\input texinfo @c -*-texinfo-*-
@c %**start of header
@setfilename slib.info
@settitle slib
@include version.txi
@setchapternewpage on
@c Choices for setchapternewpage are {on,off,odd}.
@paragraphindent 2
@defcodeindex ft
@syncodeindex ft cp
@syncodeindex tp cp
@c %**end of header

@copying
@noindent
This manual is for SLIB (version @value{SLIBVERSION}, @value{SLIBDATE}),
the portable Scheme library.

@noindent
@c Copyright (C) 1993 Todd R. Eigenschink@*
Copyright @copyright{} 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001,
2002, 2003, 2004, 2005, 2006, 2007, 2008 Free Software Foundation, Inc.

@quotation
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with no
Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.  A
copy of the license is included in the section entitled ``GNU Free
Documentation License.''
@end quotation
@end copying

@dircategory The Algorithmic Language Scheme
@direntry
* SLIB: (slib).         Scheme Library
@end direntry

@iftex
@finalout
@c DL: lose the egregious vertical whitespace, esp. around examples
@c but paras in @defun-like things don't have parindent
@parskip 4pt plus 1pt
@end iftex

@titlepage
@title SLIB
@subtitle The Portable Scheme Library
@subtitle Version @value{SLIBVERSION}, @value{SLIBDATE}
@author Aubrey Jaffer
@page
@vskip 0pt plus 1filll
@insertcopying
@end titlepage

@contents

@ifnottex
@node Top, The Library System, (dir), (dir)
@top SLIB

@insertcopying

@menu
* The Library System::          How to use and customize.
* Universal SLIB Procedures::   Provided for all implementations.
* Scheme Syntax Extension Packages::  
* Textual Conversion Packages::  
* Mathematical Packages::       
* Database Packages::           
* Other Packages::              
* About SLIB::                  Install, etc.
* Index::                       
@end menu
@end ifnottex

@node The Library System, Universal SLIB Procedures, Top, Top
@chapter The Library System

@noindent
@dfn{SLIB} is a portable library for the programming language
@dfn{Scheme}.  It provides a platform independent framework for using
@dfn{packages} of Scheme procedures and syntax.  As distributed, SLIB
contains useful packages for all Scheme implementations.  Its catalog
can be transparently extended to accomodate packages specific to a site,
implementation, user, or directory.

@menu
* Feature::                     SLIB names.
* Require::                     
* Library Catalogs::            
* Catalog Creation::            
* Catalog Vicinities::          
* Compiling Scheme::            
@end menu


@node Feature, Require, The Library System, The Library System
@section Feature

@noindent
@cindex feature
SLIB denotes @dfn{features} by symbols.  SLIB maintains a list of
features supported by a Scheme @dfn{session}.  The set of features
@cindex session
provided by a session may change during that session.  Some features
are properties of the Scheme implementation being used.  The following
@cindex intrinsic feature
@dfn{intrinsic feature}s detail what sort of numbers are available
from an implementation:

@ftindex inexact
@ftindex rational
@ftindex real
@ftindex complex
@ftindex bignum

@itemize @bullet
@item
'inexact
@item
'rational
@item
'real
@item
'complex
@item
'bignum
@end itemize

@noindent
SLIB initialization (in @file{require.scm}) tests and @dfn{provide}s
any of these numeric features which are appropriate.

@noindent
Other features correspond to the presence of packages of Scheme
procedures or syntax (macros).

@defun provided? feature
Returns @code{#t} if @var{feature} is present in the current Scheme
session; otherwise @code{#f}.  More specifically, @code{provided?}
returns @code{#t} if the symbol @var{feature} is the
@code{software-type}, the @code{scheme-implementation-type}
@footnote{scheme-implementation-type is the name symbol of the running
Scheme implementation (RScheme, |STk|, Bigloo, chez, Elk, gambit,
gauche, guile, JScheme, kawa, MacScheme, MITScheme, Pocket-Scheme, S7,
Scheme48, Scheme->C, Scheme48, Scsh, SISC, T, umb-scheme, or Vscm).
Dependence on scheme-implementation-type is almost always the wrong
way to do things.}, or if @var{feature} has been provided by a module
already loaded; and @code{#f} otherwise.

In some implementations @code{provided?} tests whether a module has
been @code{require}d by any module or in any thread; other
implementations will have @code{provided?} reflect only the modules
@code{require}d by that particular session or thread.

To work portably in both scenarios, use @code{provided?} only to test
whether intrinsic properties (like those above) are present.

The @var{feature} argument can also be an expression calling
@code{and}, @code{or}, and @code{not} of features.  The boolean result
of the logical question asked by @var{feature} is returned.
@end defun

@noindent
The generalization of @code{provided?} for arbitrary features and catalog
is @code{feature-eval}:

@defun feature-eval expression provided?
Evaluates @code{and}, @code{or}, and @code{not} forms in
@var{expression}, using the values returned by calling @var{provided?}
on the leaf symbols.  @code{feature-eval} returns the boolean result
of the logical combinations.
@end defun

@deffn {Procedure} provide feature
Informs SLIB that @var{feature} is supported in this session.
@end deffn

@example
(provided? 'foo)    @result{} #f
(provide 'foo)
(provided? 'foo)    @result{} #t
@end example

@c @defvar slib:features
@c Is a list of symbols denoting features present in this implementation.
@c @var{slib:features} can grow as modules are @code{require}d.
@c @footnote{The variables @var{*modules*} and @var{slib:features} were
@c originally modeled on variables of the same names in common-lisp.  But
@c the distinction between features native to an implementation versus
@c those provided by loading files was not useful.  The symbols in
@c @var{slib:features} now indicate the presence of a capability regardless
@c of how it was provided.}
@c @end defvar


@node Require, Library Catalogs, Feature, The Library System
@section Require

@noindent
@cindex catalog
SLIB creates and maintains a @dfn{catalog} mapping features to locations
of files introducing procedures and syntax denoted by those features.

@defvar *catalog*
Is an association list of features (symbols) and pathnames which will
supply those features.  The pathname can be either a string or a pair.
If pathname is a pair then the first element should be a macro feature
symbol, @code{source}, @code{compiled}, or one of the other cases
described in @ref{Library Catalogs}.  The cdr of the pathname should
be either a string or a list.
@end defvar

@noindent
At the beginning of each section of this manual, there is a line like
@code{(require '@var{feature})}.
@ftindex feature
The Scheme files comprising SLIB are cataloged so that these feature
names map to the corresponding files.

@noindent
SLIB provides a form, @code{require}, which loads the files providing
the requested feature.

@deffn {Procedure} require feature
@itemize @bullet
@item
If @code{(provided? @var{feature})} is true,
then @code{require} just returns.
@item
Otherwise, if @var{feature} is found in the catalog, then the
corresponding files will be loaded and @code{(provided?
@var{feature})} will henceforth return @code{#t}.  That @var{feature}
is thereafter @code{provided}.
@item
Otherwise (@var{feature} not found in the catalog), an error is
signaled.
@end itemize
@end deffn

@noindent
There is a related form @code{require-if}, used primarily for enabling
compilers to statically include modules which would be dynamically
loaded by interpreters.

@deffn {Procedure} require-if condition feature

Requires @var{feature} if @var{condition} is true.
@end deffn

@noindent
The @code{random} module uses @code{require-if} to flag
@code{object->string} as a (dynamic) required module.

@example
(require 'byte)
(require 'logical)
(require-if 'compiling 'object->string)
@end example

@noindent
The @code{batch} module uses @code{require-if} to flag
@code{posix-time} as a module to load if the implementation supports
large precision exact integers.

@example
(require-if '(and bignum compiling) 'posix-time)
@end example

@noindent
The catalog can also be queried using @code{slib:in-catalog?}.

@defun slib:in-catalog? feature
Returns a @code{CDR} of the catalog entry if one was found for the
symbol @var{feature} in the alist @code{*catalog*} (and transitively
through any symbol aliases encountered).  Otherwise, returns
@code{#f}.  The format of catalog entries is explained in
@ref{Library Catalogs}.
@end defun


@node Library Catalogs, Catalog Creation, Require, The Library System
@section Library Catalogs

@noindent
Catalog files consist of one or more @dfn{association list}s.
@cindex Catalog File
In the circumstance where a feature symbol appears in more than one
list, the latter list's association is retrieved.  Here are the
supported formats for elements of catalog lists:

@table @code
@item (@var{feature} . @i{<symbol>})
Redirects to the feature named @i{<symbol>}.
@item (@var{feature} . "@i{<path>}")
Loads file @i{<path>}.
@item (@var{feature} source "@i{<path>"})
@cindex source
@code{slib:load}s the Scheme source file @i{<path>}.
@item (@var{feature} compiled "@i{<path>"} @dots{})
@cindex compiled
@code{slib:load-compiled}s the files @i{<path>} @dots{}.
@item (@var{feature} aggregate @i{<symbol>} @dots{})
@cindex aggregate
@code{require}s the features @i{<symbol>} @dots{}.
@end table

@noindent
The various macro styles first @code{require} the named macro package,
then just load @i{<path>} or load-and-macro-expand @i{<path>} as
appropriate for the implementation.

@table @code
@item (@var{feature} defmacro "@i{<path>"})
@cindex defmacro
@code{defmacro:load}s the Scheme source file @i{<path>}.
@item (@var{feature} macro-by-example "@i{<path>"})
@cindex macro-by-example
@code{defmacro:load}s the Scheme source file @i{<path>}.
@end table

@table @code
@item (@var{feature} macro "@i{<path>"})
@cindex macro
@code{macro:load}s the Scheme source file @i{<path>}.
@item (@var{feature} macros-that-work "@i{<path>"})
@cindex macros-that-work
@code{macro:load}s the Scheme source file @i{<path>}.
@item (@var{feature} syntax-case "@i{<path>"})
@cindex syntax-case
@code{macro:load}s the Scheme source file @i{<path>}.
@item (@var{feature} syntactic-closures "@i{<path>"})
@cindex syntactic-closures
@code{macro:load}s the Scheme source file @i{<path>}.
@end table


@node Catalog Creation, Catalog Vicinities, Library Catalogs, The Library System
@section Catalog Creation

@noindent
At the start of an interactive session no catalog is present, but is
created with the first catalog inquiry (such as @code{(require
'random)}).  Several sources of catalog information are combined to
produce the catalog:

@itemize @bullet
@item
standard SLIB packages.
@item
additional packages of interest to this site.
@item
packages specifically for the variety of Scheme which this session is
running.  This catalog, if it exists, is the file @file{implcat} in
@code{implementation-invicinity}, which is created by loading
@file{mkimpcat.scm} in @code{implementation-invicinity} if it exists.
@item
packages this user wants to always have available.  This catalog is the
file @file{homecat} in the user's @dfn{HOME} directory.
@cindex HOME
@item
packages germane to working in this (current working) directory.  This
catalog is the file @file{usercat} in the directory to which it applies.
One would typically @code{cd} to this directory before starting the
Scheme session.
@item
packages which are part of an application program.
@end itemize

@noindent
SLIB combines the catalog information which doesn't vary per user into
the file @file{slibcat} in the implementation-vicinity.  Therefore
@file{slibcat} needs change only when new software is installed or
compiled.  Because the actual pathnames of files can differ from
installation to installation, SLIB builds a separate catalog for each
implementation it is used with.

@noindent
The definition of @code{*slib-version*} in SLIB file
@file{require.scm} is checked against the catalog association of
@code{*slib-version*} to ascertain when versions have changed.  It is
a reasonable practice to change the definition of
@code{*slib-version*} whenever the library is changed.  If multiple
implementations of Scheme use SLIB, remember that recompiling one
@file{slibcat} will update only that implementation's catalog.

@noindent
The compilation scripts of Scheme implementations which work with SLIB
can automatically trigger catalog compilation by deleting
@file{slibcat} or by invoking @code{require} of a special feature:

@deffn {Procedure} require @r{'new-catalog}
@cindex new-catalog
This will load @file{mklibcat}, which compiles and writes a new
@file{slibcat}.
@end deffn

@noindent
Another special feature of @code{require} erases SLIB's catalog,
forcing it to be reloaded the next time the catalog is queried.

@deffn {Procedure} require @r{#f}
Removes SLIB's catalog information.  This should be done before saving
an executable image so that, when restored, its catalog will be loaded
afresh.
@end deffn


@node Catalog Vicinities, Compiling Scheme, Catalog Creation, The Library System
@section Catalog Vicinities

@noindent
Each file in the table below is descibed in terms of its
file-system independent @dfn{vicinity} (@pxref{Vicinity}).  The entries
of a catalog in the table override those of catalogs above it in the
table.

@table @asis

@item @code{implementation-vicinity} @file{slibcat}
@cindex slibcat
This file contains the associations for the packages comprising SLIB,
the @file{implcat} and the @file{sitecat}s.  The associations in the
other catalogs override those of the standard catalog.

@item @code{library-vicinity} @file{mklibcat.scm}
@cindex mklibcat.scm
creates @file{slibcat}.

@item @code{library-vicinity} @file{sitecat}
@cindex sitecat
This file contains the associations specific to an SLIB installation.

@item @code{implementation-vicinity} @file{implcat}
@cindex implcat
This file contains the associations specific to an implementation of
Scheme.  Different implementations of Scheme should have different
@code{implementation-vicinity}.

@item @code{implementation-vicinity} @file{mkimpcat.scm}
@cindex mkimpcat.scm
if present, creates @file{implcat}.

@item @code{implementation-vicinity} @file{sitecat}
@cindex sitecat
This file contains the associations specific to a Scheme implementation
installation.

@item @code{home-vicinity} @file{homecat}
@cindex homecat
This file contains the associations specific to an SLIB user.

@item @code{user-vicinity} @file{usercat}
@cindex usercat
This file contains associations affecting only those sessions whose
@dfn{working directory} is @code{user-vicinity}.

@end table

@noindent
Here is an example of a @file{usercat} catalog.  A program in this
directory can invoke the @samp{run} feature with @code{(require 'run)}.

@example
;;; "usercat": SLIB catalog additions for SIMSYNCH.     -*-scheme-*-
(
 (simsynch      . "../synch/simsynch.scm")
 (run           . "../synch/run.scm")
 (schlep        . "schlep.scm")
)
@end example

@noindent
Copying @file{usercat} to many directories is inconvenient.
Application programs which aren't always run in specially prepared
directories can nonetheless register their features during
initialization.

@deffn {Procedure} catalog:read vicinity catalog
Reads file named by string @var{catalog} in @var{vicinity}, resolving
all paths relative to @var{vicinity}, and adds those feature
associations to @var{*catalog*}.

@code{catalog:read} would typically be used by an application program
having dynamically loadable modules.  For instance, to register
factoring and other modules in @var{*catalog*}, JACAL does:

@example
(catalog:read (program-vicinity) "jacalcat")
@end example

@end deffn

@noindent
For an application program there are three appropriate venues for
registering its catalog associations:

@itemize @bullet
@item
in a @file{usercat} file in the directory where the program runs; or
@item
in an @file{implcat} file in the @code{implementation-vicinity}; or
@item
in an application program directory; loaded by calling
@code{catalog:read}.
@end itemize


@node Compiling Scheme,  , Catalog Vicinities, The Library System
@section Compiling Scheme

To use Scheme compilers effectively with SLIB the compiler needs to
know which SLIB modules are to be compiled and which symbols are
exported from those modules.

The procedures in this section automate the extraction of this
information from SLIB modules.  They are guaranteed to work on SLIB
modules; to use them on other sources, those sources should follow
SLIB conventions.

@menu
* Module Conventions::          
* Module Manifests::            
* Module Semantics::            
* Top-level Variable References::  
* Module Analysis::             
@end menu

@node Module Conventions, Module Manifests, Compiling Scheme, Compiling Scheme
@subsection Module Conventions

@itemize @bullet
@item
All the top-level @code{require} commands have one quoted argument and
are positioned before other Scheme definitions and expressions in the
file.
@item
Any conditionally @code{require}d SLIB modules
@footnote{There are some functions with internal @code{require} calls
to delay loading modules until they are needed.  While this reduces
startup latency for interpreters, it can produce headaches for
compilers.}
also appear at the beginning of their files conditioned on the feature
@cindex compiling
@code{compiling} using @code{require-if}
(@pxref{Require, require-if}).

@example
(require 'logical)
(require 'multiarg/and-)
(require-if 'compiling 'sort)
(require-if 'compiling 'ciexyz)
@end example

@item
Schmooz-style comments preceding a definition, identify that
definition as an exported identifier (@pxref{Schmooz}).  For
non-schmooz files, putting @samp{;@@} at the beginning of the line
immediately preceding the definition (@code{define},
@code{define-syntax}, or @code{defmacro}) suffices.

@example
;@@
(define (identity <obj>) <obj>)
@end example

@item
Syntax (macro) definitions are grouped at the end of a module file.

@item
Modules defining macros do not invoke those macros.  SLIB macro
implementations are exempt from this rule.

An example of how to expand macro invocations is:

@example
(require 'macros-that-work)
(require 'yasos)
(require 'pprint-file)
(pprint-filter-file "collect.scm" macwork:expand)
@end example

@end itemize


@node Module Manifests, Module Semantics, Module Conventions, Compiling Scheme
@subsection Module Manifests

@include manifest.txi


@node Module Semantics, Top-level Variable References, Module Manifests, Compiling Scheme
@subsection Module Semantics

For the purpose of compiling Scheme code, each top-level
@code{require} makes the identifiers exported by its feature's module
@code{defined} (or defmacroed or defined-syntaxed) within the file
(being compiled) headed with those requires.

Top-level occurrences of @code{require-if} make defined the exports
from the module named by the second argument @emph{if} the
@var{feature-expression} first argument is true in the target
environment.  The target feature @code{compiling} should be provided
during this phase of compilation.

Non-top-level SLIB occurences of @code{require} and @code{require-if}
of quoted features can be ignored by compilers.  The SLIB modules will
all have top-level constructs for those features.

@cindex aggregate
Note that aggregate catalog entries import more than one module.
Implementations of @code{require} may or may @emph{not} be transitive;
code which uses module exports without requiring the providing module
is in error.

In the SLIB modules @code{modular}, @code{batch}, @code{hash},
@code{common-lisp-time}, @code{commutative-ring}, @code{charplot},
@code{logical}, @code{common-list-functions}, @code{coerce} and
@code{break} there is code conditional on features being
@code{provided?}.  Most are testing for the presence of features which
are intrinsic to implementations (inexacts, bignums, ...).

In all cases these @code{provided?} tests can be evaluated at
compile-time using @code{feature-eval}
(@pxref{Feature, feature-eval}).  The simplest way to compile these
constructs may be to treat @code{provided?} as a macro.


@node Top-level Variable References, Module Analysis, Module Semantics, Compiling Scheme
@subsection Top-level Variable References

@include top-refs.txi


@node Module Analysis,  , Top-level Variable References, Compiling Scheme
@subsection Module Analysis

@include vet.txi


@node Universal SLIB Procedures, Scheme Syntax Extension Packages, The Library System, Top
@chapter Universal SLIB Procedures

@noindent
The procedures described in these sections are supported by all
implementations as part of the @samp{*.init} files or by
@file{require.scm}.

@menu
* Vicinity::                    Pathname Management
* Configuration::               Characteristics of Scheme Implementation
* Input/Output::                Things not provided by the Scheme specs.
* System::                      LOADing, EVALing, ERRORing, and EXITing
* Miscellany::                  
@end menu

@node Vicinity, Configuration, Universal SLIB Procedures, Universal SLIB Procedures
@section Vicinity

@noindent
A vicinity is a descriptor for a place in the file system.  Vicinities
hide from the programmer the concepts of host, volume, directory, and
version.  Vicinities express only the concept of a file environment
where a file name can be resolved to a file in a system independent
manner.  Vicinities can even be used on @dfn{flat} file systems (which
have no directory structure) by having the vicinity express constraints
on the file name.

All of these procedures are file-system dependent.  Use of these
vicinity procedures can make programs file-system @emph{in}dependent.

@noindent
These procedures are provided by all implementations.
On most systems a vicinity is a string.

@defun make-vicinity dirpath
Returns @var{dirpath} as a vicinity for use as first argument to
@code{in-vicinity}.
@end defun

@defun pathname->vicinity path
Returns the vicinity containing @var{path}.
@example
(pathname->vicinity "/usr/local/lib/scm/Link.scm")
                    @result{} "/usr/local/lib/scm/"
@end example
@end defun

@defun program-vicinity
Returns the vicinity of the currently loading Scheme code.  For an
interpreter this would be the directory containing source code.  For a
compiled system (with multiple files) this would be the directory
where the object or executable files are.  If no file is currently
loading, then the result is undefined.  @strong{Warning:}
@code{program-vicinity} can return incorrect values if your program
escapes back into a @code{load} continuation.
@end defun

@defun library-vicinity
Returns the vicinity of the shared Scheme library.
@end defun

@defun implementation-vicinity
Returns the vicinity of the underlying Scheme implementation.  This
vicinity will likely contain startup code and messages and a compiler.
@end defun

@defun user-vicinity
Returns the vicinity of the current directory of the user.  On most
systems this is @file{""} (the empty string).
@end defun

@defun home-vicinity
Returns the vicinity of the user's @dfn{HOME} directory, the directory
@cindex HOME
which typically contains files which customize a computer environment
for a user.  If scheme is running without a user (eg. a daemon) or if
this concept is meaningless for the platform, then @code{home-vicinity}
returns @code{#f}.
@end defun

@c @defun scheme-file-suffix
@c Returns the default filename suffix for scheme source files.  On most
@c systems this is @samp{.scm}.
@c @end defun

@defun vicinity:suffix? chr
Returns the @samp{#t} if @var{chr} is a vicinity suffix character; and
@code{#f} otherwise.  Typical vicinity suffixes are @samp{/},
@samp{:}, and @samp{\},
@end defun

@defun in-vicinity vicinity filename
Returns a filename suitable for use by @code{slib:load},
@code{slib:load-source}, @code{slib:load-compiled},
@code{open-input-file}, @code{open-output-file}, etc.  The returned
filename is @var{filename} in @var{vicinity}.  @code{in-vicinity} should
allow @var{filename} to override @var{vicinity} when @var{filename} is
an absolute pathname and @var{vicinity} is equal to the value of
@code{(user-vicinity)}.  The behavior of @code{in-vicinity} when
@var{filename} is absolute and @var{vicinity} is not equal to the value
of @code{(user-vicinity)} is unspecified.  For most systems
@code{in-vicinity} can be @code{string-append}.
@end defun

@defun sub-vicinity vicinity name
Returns the vicinity of @var{vicinity} restricted to @var{name}.  This
is used for large systems where names of files in subsystems could
conflict.  On systems with directory structure @code{sub-vicinity} will
return a pathname of the subdirectory @var{name} of
@var{vicinity}.
@end defun

@defun with-load-pathname path thunk
@var{path} should be a string naming a file being read or loaded.
@code{with-load-pathname} evaluates @var{thunk} in a dynamic scope
where an internal variable is bound to @var{path}; the internal
variable is used for messages and @code{program-vicinity}.
@code{with-load-pathname} returns the value returned by @var{thunk}.
@end defun


@node Configuration, Input/Output, Vicinity, Universal SLIB Procedures
@section Configuration

@noindent
These constants and procedures describe characteristics of the Scheme
and underlying operating system.  They are provided by all
implementations.

@defvr Constant char-code-limit
An integer 1 larger that the largest value which can be returned by
@code{char->integer}.
@end defvr

@defvr Constant most-positive-fixnum
In implementations which support integers of practically unlimited size,
@var{most-positive-fixnum} is a large exact integer within the range of
exact integers that may result from computing the length of a list,
vector, or string.

In implementations which do not support integers of practically
unlimited size, @var{most-positive-fixnum} is the largest exact integer
that may result from computing the length of a list, vector, or string.
@end defvr

@defvr Constant slib:tab
The tab character.
@end defvr

@defvr Constant slib:form-feed
The form-feed character.
@end defvr

@defun software-type
Returns a symbol denoting the generic operating system type.  For
instance, @code{unix}, @code{vms}, @code{macos}, @code{amiga}, or
@code{ms-dos}.
@end defun

@defun slib:report-version
Displays the versions of SLIB and the underlying Scheme implementation
and the name of the operating system.  An unspecified value is returned.

@example
(slib:report-version) @result{} slib "@value{SLIBVERSION}" on scm "5b1" on unix
@end example
@end defun

@defun slib:report
Displays the information of @code{(slib:report-version)} followed by
almost all the information neccessary for submitting a problem report.
An unspecified value is returned.
@end defun

@defun slib:report #t
provides a more verbose listing.
@end defun

@defun slib:report filename
Writes the verbose report to file @file{filename}.

@example
(slib:report)
@result{}
slib "@value{SLIBVERSION}" on scm "5b1" on unix
(implementation-vicinity) is "/usr/local/lib/scm/"
(library-vicinity) is "/usr/local/lib/slib/"
(scheme-file-suffix) is ".scm"
loaded slib:features :
        trace alist qp sort
        common-list-functions macro values getopt
        compiled
implementation slib:features :
        bignum complex real rational
        inexact vicinity ed getenv
        tmpnam abort transcript with-file
        ieee-p1178 r4rs rev4-optional-procedures hash
        object-hash delay eval dynamic-wind
        multiarg-apply multiarg/and- logical defmacro
        string-port source current-time record
        rev3-procedures rev2-procedures sun-dl string-case
        array dump char-ready? full-continuation
        system
implementation *catalog* :
        (i/o-extensions compiled "/usr/local/lib/scm/ioext.so")
        ...
@end example
@end defun


@node Input/Output, System, Configuration, Universal SLIB Procedures
@section Input/Output

@noindent
These procedures are provided by all implementations.

@defun file-exists? filename
Returns @code{#t} if the specified file exists.  Otherwise, returns
@code{#f}.  If the underlying implementation does not support this
feature then @code{#f} is always returned.
@end defun

@defun delete-file filename
Deletes the file specified by @var{filename}.  If @var{filename} can not
be deleted, @code{#f} is returned.  Otherwise, @code{#t} is
returned.
@end defun

@defun open-file filename modes
@var{filename} should be a string naming a file.  @code{open-file}
returns a port depending on the symbol @var{modes}:

@table @r
@item r
an input port capable of delivering characters from the file.
@item rb
a @emph{binary} input port capable of delivering characters from the file.
@item w
an output port capable of writing characters to a new file by that name.
@item wb
a @emph{binary} output port capable of writing characters to a new file
by that name.
@end table

If an implementation does not distinguish between binary and non-binary
files, then it must treat @r{rb} as @r{r} and @r{wb} as @r{w}.

If the file cannot be opened, either #f is returned or an error is
signalled.  For output, if a file with the given name already exists,
the effect is unspecified.
@end defun

@defun port? obj
Returns @t{#t} if @var{obj} is an input or output port, otherwise
returns @t{#f}.
@end defun

@deffn {Procedure} close-port port
Closes the file associated with @var{port}, rendering the @var{port}
incapable of delivering or accepting characters.

@code{close-file} has no effect if the file has already been closed.
The value returned is unspecified.
@end deffn

@defun call-with-open-ports proc ports @dots{}
@defunx call-with-open-ports ports @dots{} proc
@var{Proc} should be a procedure that accepts as many arguments as there
are @var{ports} passed to @code{call-with-open-ports}.
@code{call-with-open-ports} calls @var{proc} with @var{ports} @dots{}.
If @var{proc} returns, then the ports are closed automatically and the
value yielded by the @var{proc} is returned.  If @var{proc} does not
return, then the ports will not be closed automatically unless it is
possible to prove that the ports will never again be used for a read or
write operation.
@end defun

@defun tmpnam
Returns a pathname for a file which will likely not be used by any other
process.  Successive calls to @code{(tmpnam)} will return different
pathnames.
@end defun

@defun current-error-port
Returns the current port to which diagnostic and error output is
directed.
@end defun

@deffn {Procedure} force-output
@deffnx {Procedure} force-output port
Forces any pending output on @var{port} to be delivered to the output
device and returns an unspecified value.  The @var{port} argument may be
omitted, in which case it defaults to the value returned by
@code{(current-output-port)}.
@end deffn

@defun file-position port
@defunx file-position port #f
@var{port} must be open to a file.  @code{file-position} returns the
current position of the character in @var{port} which will next be
read or written.  If the implementation does not support
file-position, then @code{#f} is returned.
@end defun

@defun file-position port k
@var{port} must be open to a file.  @code{file-position} sets the
current position in @var{port} which will next be read or written.  If
successful, @code{#t} is returned; otherwise @code{file-position}
returns @code{#f}.
@end defun

@defun output-port-width
@defunx output-port-width port

Returns the width of @var{port}, which defaults to
@code{(current-output-port)} if absent.  If the width cannot be
determined 79 is returned.
@end defun

@defun output-port-height
@defunx output-port-height port

Returns the height of @var{port}, which defaults to
@code{(current-output-port)} if absent.  If the height cannot be
determined 24 is returned.
@end defun


@node System, Miscellany, Input/Output, Universal SLIB Procedures
@section System

@noindent
These procedures are provided by all implementations.

@deffn {Procedure} slib:load-source name
Loads a file of Scheme source code from @var{name} with the default
filename extension used in SLIB.  For instance if the filename extension
used in SLIB is @file{.scm} then @code{(slib:load-source "foo")} will
load from file @file{foo.scm}.
@end deffn

@deffn {Procedure} slib:load-compiled name
On implementations which support separtely loadable compiled modules,
loads a file of compiled code from @var{name} with the implementation's
filename extension for compiled code appended.
@end deffn

@deffn {Procedure} slib:load name
Loads a file of Scheme source or compiled code from @var{name} with the
appropriate suffixes appended.  If both source and compiled code are
present with the appropriate names then the implementation will load
just one.  It is up to the implementation to choose which one will be
loaded.

If an implementation does not support compiled code then
@code{slib:load} will be identical to @code{slib:load-source}.
@end deffn

@deffn {Procedure} slib:eval obj
@code{eval} returns the value of @var{obj} evaluated in the current top
level environment.  @ref{Eval} provides a more general evaluation
facility.
@end deffn

@deffn {Procedure} slib:eval-load filename eval
@var{filename} should be a string.  If filename names an existing
file, the Scheme source code expressions and definitions are read from
the file and @var{eval} called with them sequentially.  The
@code{slib:eval-load} procedure does not affect the values returned by
@code{current-input-port}, @code{current-error-port}, and
@code{current-output-port}.
@end deffn

@deffn {Procedure} slib:warn arg1 arg2 @dots{}
Outputs a warning message containing the arguments.
@end deffn

@deffn {Procedure} slib:error arg1 arg2 @dots{}
Outputs an error message containing the arguments, aborts evaluation of
the current form and responds in a system dependent way to the error.
Typical responses are to abort the program or to enter a read-eval-print
loop.
@end deffn

@deffn {Procedure} slib:exit n
@deffnx {Procedure} slib:exit
Exits from the Scheme session returning status @var{n} to the system.
If @var{n} is omitted or @code{#t}, a success status is returned to
the system (if possible).  If @var{n} is @code{#f} a failure is
returned to the system (if possible).  If @var{n} is an integer, then
@var{n} is returned to the system (if possible).  If the Scheme
session cannot exit, then an unspecified value is returned from
@code{slib:exit}.
@end deffn

@defun browse-url url
Web browsers have become so ubiquitous that programming languagues
should support a uniform interface to them.

If a browser is running, @code{browse-url} causes the browser to
display the page specified by string @var{url} and returns @code{#t}.

If the browser is not running, @code{browse-url} starts a browser
displaying the argument @var{url}.  If the browser starts as a
background job, @code{browse-url} returns @code{#t} immediately; if
the browser starts as a foreground job, then @code{browse-url} returns
@code{#t} when the browser exits; otherwise (if no browser) it returns
@code{#f}.
@end defun


@node Miscellany,  , System, Universal SLIB Procedures
@section Miscellany

These procedures are provided by all implementations.

@defun identity x
@var{identity} returns its argument.

Example:
@lisp
(identity 3)
   @result{} 3
(identity '(foo bar))
   @result{} (foo bar)
(map identity @var{lst})
   @equiv{} (copy-list @var{lst})
@end lisp
@end defun


@subsection Mutual Exclusion

@noindent
An @dfn{exchanger} is a procedure of one argument regulating mutually
@cindex exchanger
exclusive access to a resource.  When a exchanger is called, its current
content is returned, while being replaced by its argument in an atomic
operation.

@defun make-exchanger obj

Returns a new exchanger with the argument @var{obj} as its initial
content.

@example
(define queue (make-exchanger (list a)))
@end example

A queue implemented as an exchanger holding a list can be protected from
reentrant execution thus:

@example
(define (pop queue)
  (let ((lst #f))
    (dynamic-wind
        (lambda () (set! lst (queue #f)))
        (lambda () (and lst (not (null? lst))
                        (let ((ret (car lst)))
                          (set! lst (cdr lst))
                          ret)))
        (lambda () (and lst (queue lst))))))

(pop queue)         @result{} a

(pop queue)         @result{} #f
@end example
@end defun


@subsection Legacy

@noindent
The following procedures were present in Scheme until R4RS
(@pxref{Notes, , Language changes ,r4rs, Revised(4) Scheme}).
They are provided by all SLIB implementations.

@defvr Constant t
Defined as @code{#t}.
@end defvr

@defvr Constant nil
Defined as @code{#f}.
@end defvr

@defun last-pair l
Returns the last pair in the list @var{l}.  Example:
@lisp
(last-pair (cons 1 2))
   @result{} (1 . 2)
(last-pair '(1 2))
   @result{} (2)
    @equiv{} (cons 2 '())
@end lisp
@end defun


@node Scheme Syntax Extension Packages, Textual Conversion Packages, Universal SLIB Procedures, Top
@chapter Scheme Syntax Extension Packages

@menu
* Defmacro::                    Supported by all implementations

* R4RS Macros::                 'macro
* Macro by Example::            'macro-by-example
* Macros That Work::            'macros-that-work
* Syntactic Closures::          'syntactic-closures
* Syntax-Case Macros::          'syntax-case

Syntax extensions (macros) included with SLIB.

* Define-Structure::            'structure
* Define-Record-Type::          'define-record-type, 'srfi-9
* Fluid-Let::                   'fluid-let
* Parameter Objects::           'srfi-39
* Binding to multiple values::  'receive, 'srfi-8
* Guarded LET* special form::   'and-let*, 'srfi-2
* Guarded COND Clause::         'guarded-cond-clause, 'srfi-61
* Yasos::                       'yasos, 'oop, 'collect
@end menu

@node Defmacro, R4RS Macros, Scheme Syntax Extension Packages, Scheme Syntax Extension Packages
@section Defmacro

Defmacros are supported by all implementations.
@c See also @code{gentemp}, in @ref{Macros}.

@defun gentemp
Returns a new (interned) symbol each time it is called.  The symbol
names are implementation-dependent
@lisp
(gentemp) @result{} scm:G0
(gentemp) @result{} scm:G1
@end lisp
@end defun

@defun defmacro:eval e
Returns the @code{slib:eval} of expanding all defmacros in scheme
expression @var{e}.
@end defun

@defun defmacro:load filename
@var{filename} should be a string.  If filename names an existing
file, the @code{defmacro:load} procedure reads Scheme source code
expressions and definitions from the file and evaluates them
sequentially.  These source code expressions and definitions may
contain defmacro definitions.  The @code{defmacro:load} procedure does
not affect the values returned by @code{current-input-port},
@code{current-error-port}, and @code{current-output-port}.
@end defun

@defun defmacro? sym
Returns @code{#t} if @var{sym} has been defined by @code{defmacro},
@code{#f} otherwise.
@end defun

@defun macroexpand-1 form
@defunx macroexpand form
If @var{form} is a macro call, @code{macroexpand-1} will expand the
macro call once and return it.  A @var{form} is considered to be a macro
call only if it is a cons whose @code{car} is a symbol for which a
@code{defmacro} has been defined.

@code{macroexpand} is similar to @code{macroexpand-1}, but repeatedly
expands @var{form} until it is no longer a macro call.
@end defun

@defmac defmacro name lambda-list form @dots{}
When encountered by @code{defmacro:eval}, @code{defmacro:macroexpand*},
or @code{defmacro:load} defines a new macro which will henceforth be
expanded when encountered by @code{defmacro:eval},
@code{defmacro:macroexpand*}, or @code{defmacro:load}.
@end defmac

@subsection Defmacroexpand
@code{(require 'defmacroexpand)}
@ftindex defmacroexpand

@defun defmacro:expand* e
Returns the result of expanding all defmacros in scheme expression
@var{e}.
@end defun


@node R4RS Macros, Macro by Example, Defmacro, Scheme Syntax Extension Packages
@section R4RS Macros

@code{(require 'macro)} is the appropriate call if you want R4RS
@ftindex macro
high-level macros but don't care about the low level implementation.  If
an SLIB R4RS macro implementation is already loaded it will be used.
Otherwise, one of the R4RS macros implemetations is loaded.

The SLIB R4RS macro implementations support the following uniform
interface:

@defun macro:expand sexpression
Takes an R4RS expression, macro-expands it, and returns the result of
the macro expansion.
@end defun

@defun macro:eval sexpression
Takes an R4RS expression, macro-expands it, evals the result of the
macro expansion, and returns the result of the evaluation.
@end defun

@deffn {Procedure} macro:load filename
@var{filename} should be a string.  If filename names an existing
file, the @code{macro:load} procedure reads Scheme source code
expressions and definitions from the file and evaluates them
sequentially.  These source code expressions and definitions may
contain macro definitions.  The @code{macro:load} procedure does not
affect the values returned by @code{current-input-port},
@code{current-error-port}, and @code{current-output-port}.
@end deffn


@node  Macro by Example, Macros That Work, R4RS Macros, Scheme Syntax Extension Packages
@section Macro by Example

@code{(require 'macro-by-example)}
@ftindex macro-by-example

A vanilla implementation of @cite{Macro by Example} (Eugene Kohlbecker,
R4RS) by Dorai Sitaram, (dorai @@ cs.rice.edu) using @code{defmacro}.

@itemize @bullet

@item
generating hygienic global @code{define-syntax} Macro-by-Example macros
@strong{cheaply}.

@item
can define macros which use @code{...}.

@item
needn't worry about a lexical variable in a macro definition
clashing with a variable from the macro use context

@item
don't suffer the overhead of redefining the repl if @code{defmacro}
natively supported (most implementations)

@end itemize
@subsection Caveat
These macros are not referentially transparent
(@pxref{Macros, , ,r4rs, Revised(4) Scheme}).  Lexically scoped macros
(i.e., @code{let-syntax} and @code{letrec-syntax}) are not supported.
In any case, the problem
of referential transparency gains poignancy only when @code{let-syntax}
and @code{letrec-syntax} are used.  So you will not be courting
large-scale disaster unless you're using system-function names as local
variables with unintuitive bindings that the macro can't use.  However,
if you must have the full @cite{r4rs} macro functionality, look to the
more featureful (but also more expensive) versions of syntax-rules
available in slib @ref{Macros That Work}, @ref{Syntactic Closures}, and
@ref{Syntax-Case Macros}.

@defmac define-syntax keyword transformer-spec
The @var{keyword} is an identifier, and the @var{transformer-spec}
should be an instance of @code{syntax-rules}.

The top-level syntactic environment is extended by binding the
@var{keyword} to the specified transformer.

@example
(define-syntax let*
  (syntax-rules ()
    ((let* () body1 body2 ...)
     (let () body1 body2 ...))
    ((let* ((name1 val1) (name2 val2) ...)
       body1 body2 ...)
     (let ((name1 val1))
       (let* (( name2 val2) ...)
         body1 body2 ...)))))
@end example
@end defmac

@defmac syntax-rules literals syntax-rule @dots{}
@var{literals} is a list of identifiers, and each @var{syntax-rule}
should be of the form

@code{(@var{pattern} @var{template})}

where the @var{pattern} and  @var{template} are as in the grammar above.

An instance of @code{syntax-rules} produces a new macro transformer by
specifying a sequence of hygienic rewrite rules.  A use of a macro whose
keyword is associated with a transformer specified by
@code{syntax-rules} is matched against the patterns contained in the
@var{syntax-rule}s, beginning with the leftmost @var{syntax-rule}.
When a match is found, the macro use is trancribed hygienically
according to the template.

Each pattern begins with the keyword for the macro.  This keyword is not
involved in the matching and is not considered a pattern variable or
literal identifier.
@end defmac


@node Macros That Work, Syntactic Closures, Macro by Example, Scheme Syntax Extension Packages
@section Macros That Work

@code{(require 'macros-that-work)}
@ftindex macros-that-work

@cite{Macros That Work} differs from the other R4RS macro
implementations in that it does not expand derived expression types to
primitive expression types.

@defun macro:expand expression
@defunx macwork:expand expression
Takes an R4RS expression, macro-expands it, and returns the result of
the macro expansion.
@end defun

@defun macro:eval expression
@defunx macwork:eval expression
@code{macro:eval} returns the value of @var{expression} in the current
top level environment.  @var{expression} can contain macro definitions.
Side effects of @var{expression} will affect the top level
environment.
@end defun

@deffn {Procedure} macro:load filename
@deffnx {Procedure} macwork:load filename
@var{filename} should be a string.  If filename names an existing
file, the @code{macro:load} procedure reads Scheme source code
expressions and definitions from the file and evaluates them
sequentially.  These source code expressions and definitions may
contain macro definitions.  The @code{macro:load} procedure does not
affect the values returned by @code{current-input-port},
@code{current-error-port}, and @code{current-output-port}.
@end deffn

References:

The @cite{Revised^4 Report on the Algorithmic Language Scheme} Clinger
and Rees [editors].  To appear in LISP Pointers.  Also available as a
technical report from the University of Oregon, MIT AI Lab, and
Cornell.

@center Macros That Work.  Clinger and Rees.  POPL '91.

The supported syntax differs from the R4RS in that vectors are allowed
as patterns and as templates and are not allowed as pattern or template
data.

@example
transformer spec  @expansion{}  (syntax-rules literals rules)

rules  @expansion{}  ()
         |  (rule . rules)

rule  @expansion{}  (pattern template)

pattern  @expansion{}  pattern_var      ; a symbol not in literals
           |  symbol           ; a symbol in literals
           |  ()
           |  (pattern . pattern)
           |  (ellipsis_pattern)
           |  #(pattern*)                     ; extends R4RS
           |  #(pattern* ellipsis_pattern)    ; extends R4RS
           |  pattern_datum

template  @expansion{}  pattern_var
            |  symbol
            |  ()
            |  (template2 . template2)
            |  #(template*)                   ; extends R4RS
            |  pattern_datum

template2  @expansion{}  template
             |  ellipsis_template

pattern_datum  @expansion{}  string                    ; no vector
                 |  character
                 |  boolean
                 |  number

ellipsis_pattern  @expansion{} pattern ...

ellipsis_template  @expansion{}  template ...

pattern_var  @expansion{}  symbol   ; not in literals

literals  @expansion{}  ()
            |  (symbol . literals)
@end example

@subsection Definitions

@table @asis

@item Scope of an ellipsis
Within a pattern or template, the scope of an ellipsis (@code{...}) is
the pattern or template that appears to its left.

@item Rank of a pattern variable
The rank of a pattern variable is the number of ellipses within whose
scope it appears in the pattern.

@item Rank of a subtemplate
The rank of a subtemplate is the number of ellipses within whose scope
it appears in the template.

@item Template rank of an occurrence of a pattern variable
The template rank of an occurrence of a pattern variable within a
template is the rank of that occurrence, viewed as a subtemplate.

@item Variables bound by a pattern
The variables bound by a pattern are the pattern variables that appear
within it.

@item Referenced variables of a subtemplate
The referenced variables of a subtemplate are the pattern variables that
appear within it.

@item Variables opened by an ellipsis template
The variables opened by an ellipsis template are the referenced pattern
variables whose rank is greater than the rank of the ellipsis template.

@end table

@subsection Restrictions

No pattern variable appears more than once within a pattern.

For every occurrence of a pattern variable within a template, the
template rank of the occurrence must be greater than or equal to the
pattern variable's rank.

Every ellipsis template must open at least one variable.

For every ellipsis template, the variables opened by an ellipsis
template must all be bound to sequences of the same length.

The compiled form of a @var{rule} is

@example
rule  @expansion{}  (pattern template inserted)

pattern  @expansion{}  pattern_var
           |  symbol
           |  ()
           |  (pattern . pattern)
           |  ellipsis_pattern
           |  #(pattern)
           |  pattern_datum

template  @expansion{}  pattern_var
            |  symbol
            |  ()
            |  (template2 . template2)
            |  #(pattern)
            |  pattern_datum

template2  @expansion{}  template
             |  ellipsis_template

pattern_datum  @expansion{}  string
                 |  character
                 |  boolean
                 |  number

pattern_var  @expansion{}  #(V symbol rank)

ellipsis_pattern  @expansion{}  #(E pattern pattern_vars)

ellipsis_template  @expansion{}  #(E template pattern_vars)

inserted  @expansion{}  ()
            |  (symbol . inserted)

pattern_vars  @expansion{}  ()
                |  (pattern_var . pattern_vars)

rank  @expansion{}  exact non-negative integer
@end example

where V and E are unforgeable values.

The pattern variables associated with an ellipsis pattern are the
variables bound by the pattern, and the pattern variables associated
with an ellipsis template are the variables opened by the ellipsis
template.

If the template contains a big chunk that contains no pattern variables
or inserted identifiers, then the big chunk will be copied
unnecessarily.  That shouldn't matter very often.


@node Syntactic Closures, Syntax-Case Macros, Macros That Work, Scheme Syntax Extension Packages
@section Syntactic Closures

@code{(require 'syntactic-closures)}
@ftindex syntactic-closures

@defun macro:expand expression
@defunx synclo:expand expression
Returns scheme code with the macros and derived expression types of
@var{expression} expanded to primitive expression types.
@end defun

@defun macro:eval expression
@defunx synclo:eval expression
@code{macro:eval} returns the value of @var{expression} in the current
top level environment.  @var{expression} can contain macro definitions.
Side effects of @var{expression} will affect the top level
environment.
@end defun

@deffn {Procedure} macro:load filename
@deffnx {Procedure} synclo:load filename
@var{filename} should be a string.  If filename names an existing
file, the @code{macro:load} procedure reads Scheme source code
expressions and definitions from the file and evaluates them
sequentially.  These source code expressions and definitions may
contain macro definitions.  The @code{macro:load} procedure does not
affect the values returned by @code{current-input-port},
@code{current-error-port}, and @code{current-output-port}.
@end deffn

@subsection Syntactic Closure Macro Facility

@center A Syntactic Closures Macro Facility
@center by Chris Hanson
@center 9 November 1991

This document describes @dfn{syntactic closures}, a low-level macro
facility for the Scheme programming language.  The facility is an
alternative to the low-level macro facility described in the
@cite{Revised^4 Report on Scheme.} This document is an addendum to that
report.

The syntactic closures facility extends the BNF rule for
@var{transformer spec} to allow a new keyword that introduces a
low-level macro transformer:

@example
@var{transformer spec} := (transformer @var{expression})
@end example

Additionally, the following procedures are added:
@lisp
make-syntactic-closure
capture-syntactic-environment
identifier?
identifier=?
@end lisp

The description of the facility is divided into three parts.  The first
part defines basic terminology.  The second part describes how macro
transformers are defined.  The third part describes the use of
@dfn{identifiers}, which extend the syntactic closure mechanism to be
compatible with @code{syntax-rules}.

@subsubsection Terminology

This section defines the concepts and data types used by the syntactic
closures facility.

@itemize @bullet

@item @dfn{Forms} are the syntactic entities out of which programs are
recursively constructed.  A form is any expression, any definition, any
syntactic keyword, or any syntactic closure.  The variable name that
appears in a @code{set!} special form is also a form.  Examples of
forms:

@lisp
17
#t
car
(+ x 4)
(lambda (x) x)
(define pi 3.14159)
if
define
@end lisp

@item An @dfn{alias} is an alternate name for a given symbol.  It can
appear anywhere in a form that the symbol could be used, and when quoted
it is replaced by the symbol; however, it does not satisfy the predicate
@code{symbol?}.  Macro transformers rarely distinguish symbols from
aliases, referring to both as identifiers.

@item A @dfn{syntactic} environment maps identifiers to their
meanings.  More precisely, it determines whether an identifier is a
syntactic keyword or a variable.  If it is a keyword, the meaning is an
interpretation for the form in which that keyword appears.  If it is a
variable, the meaning identifies which binding of that variable is
referenced.  In short, syntactic environments contain all of the
contextual information necessary for interpreting the meaning of a
particular form.

@item A @dfn{syntactic closure} consists of a form, a syntactic
environment, and a list of identifiers.  All identifiers in the form
take their meaning from the syntactic environment, except those in the
given list.  The identifiers in the list are to have their meanings
determined later.  A syntactic closure may be used in any context in
which its form could have been used.  Since a syntactic closure is also
a form, it may not be used in contexts where a form would be illegal.
For example, a form may not appear as a clause in the cond special form.
A syntactic closure appearing in a quoted structure is replaced by its
form.

@end itemize

@subsubsection Transformer Definition

This section describes the @code{transformer} special form and the
procedures @code{make-syntactic-closure} and
@code{capture-syntactic-environment}.

@deffn Syntax transformer expression

Syntax: It is an error if this syntax occurs except as a
@var{transformer spec}.

Semantics: The @var{expression} is evaluated in the standard transformer
environment to yield a macro transformer as described below.  This macro
transformer is bound to a macro keyword by the special form in which the
@code{transformer} expression appears (for example,
@code{let-syntax}).

A @dfn{macro transformer} is a procedure that takes two arguments, a
form and a syntactic environment, and returns a new form.  The first
argument, the @dfn{input form}, is the form in which the macro keyword
occurred.  The second argument, the @dfn{usage environment}, is the
syntactic environment in which the input form occurred.  The result of
the transformer, the @dfn{output form}, is automatically closed in the
@dfn{transformer environment}, which is the syntactic environment in
which the @code{transformer} expression occurred.

For example, here is a definition of a push macro using
@code{syntax-rules}:

@lisp
(define-syntax  push
  (syntax-rules ()
    ((push item list)
     (set! list (cons item list)))))
@end lisp

Here is an equivalent definition using @code{transformer}:
@lisp
(define-syntax push
  (transformer
   (lambda (exp env)
     (let ((item
            (make-syntactic-closure env '() (cadr exp)))
           (list
            (make-syntactic-closure env '() (caddr exp))))
       `(set! ,list (cons ,item ,list))))))
@end lisp

In this example, the identifiers @code{set!} and @code{cons} are closed
in the transformer environment, and thus will not be affected by the
meanings of those identifiers in the usage environment
@code{env}.

Some macros may be non-hygienic by design.  For example, the following
defines a loop macro that implicitly binds @code{exit} to an escape
procedure.  The binding of @code{exit} is intended to capture free
references to @code{exit} in the body of the loop, so @code{exit} must
be left free when the body is closed:

@lisp
(define-syntax loop
  (transformer
   (lambda (exp env)
     (let ((body (cdr exp)))
       `(call-with-current-continuation
         (lambda (exit)
           (let f ()
             ,@@(map (lambda  (exp)
                       (make-syntactic-closure env '(exit)
                                               exp))
                     body)
             (f))))))))
@end lisp

To assign meanings to the identifiers in a form, use
@code{make-syntactic-closure} to close the form in a syntactic
environment.
@end deffn

@defun make-syntactic-closure environment free-names form

@var{environment} must be a syntactic environment, @var{free-names} must
be a list of identifiers, and @var{form} must be a form.
@code{make-syntactic-closure} constructs and returns a syntactic closure
of @var{form} in @var{environment}, which can be used anywhere that
@var{form} could have been used.  All the identifiers used in
@var{form}, except those explicitly excepted by @var{free-names}, obtain
their meanings from @var{environment}.

Here is an example where @var{free-names} is something other than the
empty list.  It is instructive to compare the use of @var{free-names} in
this example with its use in the @code{loop} example above: the examples
are similar except for the source of the identifier being left
free.
@lisp
(define-syntax let1
  (transformer
   (lambda (exp env)
     (let ((id (cadr exp))
           (init (caddr exp))
           (exp (cadddr exp)))
       `((lambda (,id)
           ,(make-syntactic-closure env (list id) exp))
         ,(make-syntactic-closure env '() init))))))
@end lisp

@code{let1} is a simplified version of @code{let} that only binds a
single identifier, and whose body consists of a single expression.  When
the body expression is syntactically closed in its original syntactic
environment, the identifier that is to be bound by @code{let1} must be
left free, so that it can be properly captured by the @code{lambda} in
the output form.

To obtain a syntactic environment other than the usage environment, use
@code{capture-syntactic-environment}.
@end defun

@defun capture-syntactic-environment procedure

@code{capture-syntactic-environment} returns a form that will, when
transformed, call @var{procedure} on the current syntactic environment.
@var{procedure} should compute and return a new form to be transformed,
in that same syntactic environment, in place of the form.

An example will make this clear.  Suppose we wanted to define a simple
@code{loop-until} keyword equivalent to

@lisp
(define-syntax loop-until
  (syntax-rules ()
    ((loop-until id init test return step)
     (letrec ((loop
               (lambda (id)
                 (if test return (loop step)))))
       (loop init)))))
@end lisp

The following attempt at defining @code{loop-until} has a subtle bug:
@lisp
(define-syntax loop-until
  (transformer
   (lambda (exp env)
     (let ((id (cadr exp))
           (init (caddr exp))
           (test (cadddr exp))
           (return (cadddr (cdr exp)))
           (step (cadddr (cddr exp)))
           (close
            (lambda (exp free)
              (make-syntactic-closure env free exp))))
       `(letrec ((loop
                  (lambda (,id)
                    (if ,(close test (list id))
                        ,(close return (list id))
                        (loop ,(close step (list id)))))))
          (loop ,(close init '())))))))
@end lisp

This definition appears to take all of the proper precautions to prevent
unintended captures.  It carefully closes the subexpressions in their
original syntactic environment and it leaves the @code{id} identifier
free in the @code{test}, @code{return}, and @code{step} expressions, so
that it will be captured by the binding introduced by the @code{lambda}
expression.  Unfortunately it uses the identifiers @code{if} and
@code{loop} within that @code{lambda} expression, so if the user of
@code{loop-until} just happens to use, say, @code{if} for the
identifier, it will be inadvertently captured.

The syntactic environment that @code{if} and @code{loop} want to be
exposed to is the one just outside the @code{lambda} expression: before
the user's identifier is added to the syntactic environment, but after
the identifier loop has been added.
@code{capture-syntactic-environment} captures exactly that environment
as follows:

@lisp
(define-syntax loop-until
  (transformer
   (lambda (exp env)
     (let ((id (cadr exp))
           (init (caddr exp))
           (test (cadddr exp))
           (return (cadddr (cdr exp)))
           (step (cadddr (cddr exp)))
           (close
            (lambda (exp free)
              (make-syntactic-closure env free exp))))
       `(letrec ((loop
                  ,(capture-syntactic-environment
                    (lambda (env)
                      `(lambda (,id)
                         (,(make-syntactic-closure env '() `if)
                          ,(close test (list id))
                          ,(close return (list id))
                          (,(make-syntactic-closure env '()
                                                    `loop)
                           ,(close step (list id)))))))))
          (loop ,(close init '())))))))
@end lisp

In this case, having captured the desired syntactic environment, it is
convenient to construct syntactic closures of the identifiers @code{if}
and the @code{loop} and use them in the body of the
@code{lambda}.

A common use of @code{capture-syntactic-environment} is to get the
transformer environment of a macro transformer:

@lisp
(transformer
 (lambda (exp env)
   (capture-syntactic-environment
    (lambda (transformer-env)
      ...))))
@end lisp
@end defun

@subsubsection Identifiers

This section describes the procedures that create and manipulate
identifiers.  Previous syntactic closure proposals did not have an
identifier data type -- they just used symbols.  The identifier data
type extends the syntactic closures facility to be compatible with the
high-level @code{syntax-rules} facility.

As discussed earlier, an identifier is either a symbol or an
@dfn{alias}.  An alias is implemented as a syntactic closure whose
@dfn{form} is an identifier:

@lisp
(make-syntactic-closure env '() 'a)
   @result{} an @dfn{alias}
@end lisp

Aliases are implemented as syntactic closures because they behave just
like syntactic closures most of the time.  The difference is that an
alias may be bound to a new value (for example by @code{lambda} or
@code{let-syntax}); other syntactic closures may not be used this way.
If an alias is bound, then within the scope of that binding it is looked
up in the syntactic environment just like any other identifier.

Aliases are used in the implementation of the high-level facility
@code{syntax-rules}.  A macro transformer created by @code{syntax-rules}
uses a template to generate its output form, substituting subforms of
the input form into the template.  In a syntactic closures
implementation, all of the symbols in the template are replaced by
aliases closed in the transformer environment, while the output form
itself is closed in the usage environment.  This guarantees that the
macro transformation is hygienic, without requiring the transformer to
know the syntactic roles of the substituted input subforms.

@defun identifier?  object
Returns @code{#t} if @var{object} is an identifier, otherwise returns
@code{#f}.  Examples:

@lisp
(identifier? 'a)
   @result{} #t
(identifier? (make-syntactic-closure env '() 'a))
   @result{} #t
(identifier? "a")
   @result{} #f
(identifier? #\a)
   @result{} #f
(identifier? 97)
   @result{} #f
(identifier? #f)
   @result{} #f
(identifier? '(a))
   @result{} #f
(identifier? '#(a))
   @result{} #f
@end lisp

The predicate @code{eq?} is used to determine if two identifers are
``the same''.  Thus @code{eq?} can be used to compare identifiers
exactly as it would be used to compare symbols.  Often, though, it is
useful to know whether two identifiers ``mean the same thing''.  For
example, the @code{cond} macro uses the symbol @code{else} to identify
the final clause in the conditional.  A macro transformer for
@code{cond} cannot just look for the symbol @code{else}, because the
@code{cond} form might be the output of another macro transformer that
replaced the symbol @code{else} with an alias.  Instead the transformer
must look for an identifier that ``means the same thing'' in the usage
environment as the symbol @code{else} means in the transformer
environment.
@end defun

@defun identifier=? environment1 identifier1 environment2 identifier2
@var{environment1} and @var{environment2} must be syntactic
environments, and @var{identifier1} and @var{identifier2} must be
identifiers.  @code{identifier=?} returns @code{#t} if the meaning of
@var{identifier1} in @var{environment1} is the same as that of
@var{identifier2} in @var{environment2}, otherwise it returns @code{#f}.
Examples:

@lisp
(let-syntax
    ((foo
      (transformer
       (lambda (form env)
         (capture-syntactic-environment
          (lambda (transformer-env)
            (identifier=? transformer-env 'x env 'x)))))))
  (list (foo)
        (let ((x 3))
          (foo))))
   @result{} (#t #f)
@end lisp

@lisp
(let-syntax ((bar foo))
  (let-syntax
      ((foo
        (transformer
         (lambda (form env)
           (capture-syntactic-environment
            (lambda (transformer-env)
              (identifier=? transformer-env 'foo
                            env (cadr form))))))))
    (list (foo foo)
          (foobar))))
   @result{} (#f #t)
@end lisp
@end defun

@subsubsection Acknowledgements

The syntactic closures facility was invented by Alan Bawden and Jonathan
Rees.  The use of aliases to implement @code{syntax-rules} was invented
by Alan Bawden (who prefers to call them @dfn{synthetic names}).  Much
of this proposal is derived from an earlier proposal by Alan
Bawden.


@node Syntax-Case Macros, Define-Structure, Syntactic Closures, Scheme Syntax Extension Packages
@section Syntax-Case Macros

@code{(require 'syntax-case)}
@ftindex syntax-case

@defun macro:expand expression
@defunx syncase:expand expression
Returns scheme code with the macros and derived expression types of
@var{expression} expanded to primitive expression types.
@end defun

@defun macro:eval expression
@defunx syncase:eval expression
@code{macro:eval} returns the value of @var{expression} in the current
top level environment.  @var{expression} can contain macro definitions.
Side effects of @var{expression} will affect the top level
environment.
@end defun

@deffn {Procedure} macro:load filename
@deffnx {Procedure} syncase:load filename
@var{filename} should be a string.  If filename names an existing
file, the @code{macro:load} procedure reads Scheme source code
expressions and definitions from the file and evaluates them
sequentially.  These source code expressions and definitions may
contain macro definitions.  The @code{macro:load} procedure does not
affect the values returned by @code{current-input-port},
@code{current-error-port}, and @code{current-output-port}.
@end deffn

This is version 2.1 of @code{syntax-case}, the low-level macro facility
proposed and implemented by Robert Hieb and R. Kent Dybvig.

This version is further adapted by Harald Hanche-Olsen
<hanche @@ imf.unit.no> to make it compatible with, and easily usable
with, SLIB.  Mainly, these adaptations consisted of:

@itemize @bullet
@item
Removing white space from @file{expand.pp} to save space in the
distribution.  This file is not meant for human readers anyway@dots{}

@item
Removed a couple of Chez scheme dependencies.

@item
Renamed global variables used to minimize the possibility of name
conflicts.

@item
Adding an SLIB-specific initialization file.

@item
Removing a couple extra files, most notably the documentation (but see
below).
@end itemize

If you wish, you can see exactly what changes were done by reading the
shell script in the file @file{syncase.sh}.

The two PostScript files were omitted in order to not burden the SLIB
distribution with them.  If you do intend to use @code{syntax-case},
however, you should get these files and print them out on a PostScript
printer.  They are available with the original @code{syntax-case}
distribution by anonymous FTP in
@file{cs.indiana.edu:/pub/scheme/syntax-case}.

In order to use syntax-case from an interactive top level, execute:
@lisp
(require 'syntax-case)
@ftindex syntax-case
(require 'repl)
@ftindex repl
(repl:top-level macro:eval)
@end lisp
See the section Repl (@pxref{Repl}) for more information.

To check operation of syntax-case get
@file{cs.indiana.edu:/pub/scheme/syntax-case}, and type
@lisp
(require 'syntax-case)
@ftindex syntax-case
@findex syncase:sanity-check
(syncase:sanity-check)
@end lisp

Beware that @code{syntax-case} takes a long time to load -- about 20s on
a SPARCstation SLC (with SCM) and about 90s on a Macintosh SE/30 (with
Gambit).

@subsection Notes

All R4RS syntactic forms are defined, including @code{delay}.  Along
with @code{delay} are simple definitions for @code{make-promise} (into
which @code{delay} expressions expand) and @code{force}.

@code{syntax-rules} and @code{with-syntax} (described in @cite{TR356})
are defined.

@code{syntax-case} is actually defined as a macro that expands into
calls to the procedure @code{syntax-dispatch} and the core form
@code{syntax-lambda}; do not redefine these names.

Several other top-level bindings not documented in TR356 are created:
@itemize @bullet
@item the ``hooks'' in @file{hooks.ss}
@item the @code{build-} procedures in @file{output.ss}
@item @code{expand-syntax} (the expander)
@end itemize

The syntax of define has been extended to allow @code{(define @var{id})},
which assigns @var{id} to some unspecified value.

We have attempted to maintain R4RS compatibility where possible.  The
incompatibilities should be confined to @file{hooks.ss}.  Please let us
know if there is some incompatibility that is not flagged as such.

Send bug reports, comments, suggestions, and questions to Kent Dybvig
(dyb @@ iuvax.cs.indiana.edu).


@node Define-Structure, Define-Record-Type, Syntax-Case Macros, Scheme Syntax Extension Packages
@section Define-Structure

@code{(require 'structure)}

@noindent
Included with the @code{syntax-case} files was @file{structure.scm}
which defines a macro @code{define-structure}.  Here is its
documentation from Gambit-4.0:

@deffn {special form} define-structure (@var{name} @var{field}@dots{})

Record data types similar to Pascal records and C @code{struct}
types can be defined using the @code{define-structure} special form.
The identifier @var{name} specifies the name of the new data type.  The
structure name is followed by @var{k} identifiers naming each field of
the record.  The @code{define-structure} expands into a set of definitions
of the following procedures:

@itemize @bullet{}

@item
`@t{make-}@var{name}' -- A @var{k} argument procedure which constructs
a new record from the value of its @var{k} fields.

@item
`@var{name}@t{?}' -- A procedure which tests if its single argument
is of the given record type.

@item
`@var{name}@t{-}@var{field}' -- For each field, a procedure taking
as its single argument a value of the given record type and returning
the content of the corresponding field of the record.

@item
`@var{name}@t{-}@var{field}@t{-set!}' -- For each field, a two
argument procedure taking as its first argument a value of the given
record type.  The second argument gets assigned to the corresponding
field of the record and the void object is returned.

@end itemize

Gambit record data types have a printed representation that includes
the name of the type and the name and value of each field.

For example:

@smallexample
> @b{(require 'syntax-case)}
> @b{(require 'repl)}
> @b{(repl:top-level macro:eval)}
> @b{(require 'structure)}
> @b{(define-structure (point x y color))}
> @b{(define p (make-point 3 5 'red))}
> @b{p}
#<point #3 x: 3 y: 5 color: red>
> @b{(point-x p)}
3
> @b{(point-color p)}
red
> @b{(point-color-set! p 'black)}
> @b{p}
#<point #3 x: 3 y: 5 color: black>
@end smallexample

@end deffn


@node Define-Record-Type, Fluid-Let, Define-Structure, Scheme Syntax Extension Packages
@section Define-Record-Type

@code{(require 'define-record-type)} or @code{(require 'srfi-9)}
@ftindex srfi-9
@ftindex define-record-type

@url{http://srfi.schemers.org/srfi-9/srfi-9.html}

@defspec define-record-type <type-name> (<constructor-name> <field-tag> ...) <predicate-name> <field-spec> ...

Where
@lisp
<field-spec> @equiv{} (<field-tag> <accessor-name>)
             @equiv{} (<field-tag> <accessor-name> <modifier-name>)

@end lisp

@code{define-record-type} is a syntax wrapper for the SLIB
@code{record} module.
@end defspec


@node Fluid-Let, Parameter Objects, Define-Record-Type, Scheme Syntax Extension Packages
@section Fluid-Let

@code{(require 'fluid-let)}
@ftindex fluid-let

@quotation
@emph{Note:} @code{fluid-let} is not thread-safe.  It is better to use
@ref{Parameter Objects} (srfi-39) or @ref{Dynamic Data Type}, both of
which will be made thread-safe in the future.
@end quotation

@deffn Syntax fluid-let @code{(@var{bindings} @dots{})} @var{forms}@dots{}
@end deffn
@lisp
(fluid-let ((@var{variable} @var{init}) @dots{})
   @var{expression} @var{expression} @dots{})
@end lisp

The @var{init}s are evaluated in the current environment (in some
unspecified order), the current values of the @var{variable}s are saved,
the results are assigned to the @var{variable}s, the @var{expression}s
are evaluated sequentially in the current environment, the
@var{variable}s are restored to their original values, and the value of
the last @var{expression} is returned.

The syntax of this special form is similar to that of @code{let}, but
@code{fluid-let} temporarily rebinds existing @var{variable}s.  Unlike
@code{let}, @code{fluid-let} creates no new bindings; instead it
@emph{assigns} the values of each @var{init} to the binding (determined
by the rules of lexical scoping) of its corresponding
@var{variable}.


@node Parameter Objects, Binding to multiple values, Fluid-Let, Scheme Syntax Extension Packages
@section Parameter Objects

@code{(require 'srfi-39)}
@ftindex srfi-39

@url{http://srfi.schemers.org/srfi-39/srfi-39.html}


@node Binding to multiple values, Guarded LET* special form, Parameter Objects, Scheme Syntax Extension Packages
@section Binding to multiple values

@code{(require 'receive)} or @code{(require 'srfi-8)}
@ftindex srfi-8
@ftindex receive

@defspec receive formals expression body @dots{}

@url{http://srfi.schemers.org/srfi-8/srfi-8.html}
@end defspec

@code{(require 'let-values)} or @code{(require 'srfi-11)}
@ftindex srfi-11
@ftindex let-values

@defspec let-values ((formals expression) ...) body @dots{}
@defspecx let-values* ((formals expression) ...) body @dots{}

@url{http://srfi.schemers.org/srfi-11/srfi-11.html}
@end defspec


@node Guarded LET* special form, Guarded COND Clause, Binding to multiple values, Scheme Syntax Extension Packages
@section Guarded LET* special form

@code{(require 'and-let*)} or @code{(require 'srfi-2)}
@ftindex srfi-2
@ftindex and-let*

@defmac and-let* claws body @dots{}

@url{http://srfi.schemers.org/srfi-2/srfi-2.html}
@end defmac


@node Guarded COND Clause, Yasos, Guarded LET* special form, Scheme Syntax Extension Packages
@section Guarded COND Clause

@code{(require 'guarded-cond-clause)} or @code{(require 'srfi-61)}
@ftindex srfi-61
@ftindex guarded-cond-clause

@url{http://srfi.schemers.org/srfi-61/srfi-61.html}

@deffn {library syntax} cond  <clause1> <clause2> @dots{}

@emph{Syntax:}
Each @r{<clause>} should be of the form

@format
@t{(@r{<test>} @r{<expression1>} @dots{})
}
@end format

where @r{<test>} is any expression.  Alternatively, a @r{<clause>} may be
of the form

@format
@t{(@r{<test>} => @r{<expression>})
}
@end format

The @r{<clause>} production in the formal syntax of Scheme as
written by R5RS in section 7.1.3 is extended with a new option:
@cindex @w{=>}

@format
@t{@r{<clause>} => (@r{<generator>} @r{<guard>} => @r{<receiver>})
}
@end format

where @r{<generator>}, @r{<guard>}, & @r{<receiver>} are all
@r{<expression>}s.

@quotation
Clauses of this form have the following semantics: @r{<generator>} is
evaluated.  It may return arbitrarily many values.  @r{<Guard>} is
applied to an argument list containing the values in order that
@r{<generator>} returned.  If @r{<guard>} returns a true value for
that argument list, @r{<receiver>} is applied with an equivalent
argument list.  If @r{<guard>} returns a false value, however, the
clause is abandoned and the next one is tried.
@end quotation

The last @r{<clause>} may be
an ``else clause,'' which has the form

@format
@t{(else @r{<expression1>} @r{<expression2>} @dots{})@r{.}
}
@end format
@end deffn

@noindent
This @code{port->char-list} procedure accepts an input port and
returns a list of all the characters it produces until the end.

@example
(define (port->char-list port)
  (cond ((read-char port) char?
         => (lambda (c) (cons c (port->char-list port))))
        (else '())))

(call-with-input-string "foo" port->char-list)  ==>  (#\f #\o #\o)
@end example


@node Yasos,  , Guarded COND Clause, Scheme Syntax Extension Packages
@section Yasos

@c Much of the documentation in this section was written by Dave Love
@c (d.love@dl.ac.uk) -- don't blame Ken Dickey for its faults.
@c but we can blame him for not writing it!

@code{(require 'oop)} or @code{(require 'yasos)}
@ftindex oop
@ftindex yasos

`Yet Another Scheme Object System' is a simple object system for Scheme
based on the paper by Norman Adams and Jonathan Rees: @cite{Object
Oriented Programming in Scheme}, Proceedings of the 1988 ACM Conference
on LISP and Functional Programming, July 1988 [ACM #552880].

Another reference is:

Ken Dickey.@*
Scheming with Objects@*
@cite{AI Expert} Volume 7, Number 10 (October 1992), pp. 24-33.@*
@url{ftp://ftp.cs.indiana.edu/pub/scheme-repository/doc/pubs/swob.txt}

@menu
* Yasos terms::                 Definitions and disclaimer.
* Yasos interface::             The Yasos macros and procedures.
* Setters::                     Dylan-like setters in Yasos.
* Yasos examples::              Usage of Yasos and setters.
@end menu

@node Yasos terms, Yasos interface, Yasos, Yasos
@subsection Terms

@table @asis
@item @dfn{Object}
Any Scheme data object.

@item @dfn{Instance}
An instance of the OO system; an @dfn{object}.

@item @dfn{Operation}
A @var{method}.
@end table

@table @emph
@item Notes:
The object system supports multiple inheritance.  An instance can
inherit from 0 or more ancestors.  In the case of multiple inherited
operations with the same identity, the operation used is that from the
first ancestor which contains it (in the ancestor @code{let}).  An
operation may be applied to any Scheme data object---not just instances.
As code which creates instances is just code, there are no @dfn{classes}
and no meta-@var{anything}.  Method dispatch is by a procedure call a la
CLOS rather than by @code{send} syntax a la Smalltalk.

@item Disclaimer:
There are a number of optimizations which can be made.  This
implementation is expository (although performance should be quite
reasonable).  See the L&FP paper for some suggestions.
@end table


@node Yasos interface, Setters, Yasos terms, Yasos
@subsection Interface

@deffn Syntax define-operation @code{(}opname self arg @dots{}@code{)} @var{default-body}
Defines a default behavior for data objects which don't handle the
operation @var{opname}.  The default behavior (for an empty
@var{default-body}) is to generate an error.
@end deffn

@deffn Syntax define-predicate opname?
Defines a predicate @var{opname?}, usually used for determining the
@dfn{type} of an object, such that @code{(@var{opname?} @var{object})}
returns @code{#t} if @var{object} has an operation @var{opname?} and
@code{#f} otherwise.
@end deffn

@deffn Syntax object @code{((@var{name} @var{self} @var{arg} @dots{}) @var{body})} @dots{}
Returns an object (an instance of the object system) with operations.
Invoking @code{(@var{name} @var{object} @var{arg} @dots{})} executes the
@var{body} of the @var{object} with @var{self} bound to @var{object} and
with argument(s) @var{arg}@dots{}.
@end deffn

@deffn Syntax object-with-ancestors @code{((}ancestor1 init1@code{)} @dots{}@code{)} operation @dots{}
A @code{let}-like form of @code{object} for multiple inheritance.  It
returns an object inheriting the behaviour of @var{ancestor1} etc.  An
operation will be invoked in an ancestor if the object itself does not
provide such a method.  In the case of multiple inherited operations
with the same identity, the operation used is the one found in the first
ancestor in the ancestor list.
@end deffn

@deffn Syntax operate-as component operation self arg @dots{}
Used in an operation definition (of @var{self}) to invoke the
@var{operation} in an ancestor @var{component} but maintain the object's
identity.  Also known as ``send-to-super''.
@end deffn

@deffn {Procedure} print obj port
A default @code{print} operation is provided which is just @code{(format
@var{port} @var{obj})} (@pxref{Format}) for non-instances and prints
@var{obj} preceded by @samp{#<INSTANCE>} for instances.
@end deffn

@defun size obj
The default method returns the number of elements in @var{obj} if it is
a vector, string or list, @code{2} for a pair, @code{1} for a character
and by default id an error otherwise.  Objects such as collections
(@pxref{Collections}) may override the default in an obvious way.
@end defun


@node Setters, Yasos examples, Yasos interface, Yasos
@subsection Setters

@dfn{Setters} implement @dfn{generalized locations} for objects
associated with some sort of mutable state.  A @dfn{getter} operation
retrieves a value from a generalized location and the corresponding
setter operation stores a value into the location.  Only the getter is
named -- the setter is specified by a procedure call as below.  (Dylan
uses special syntax.)  Typically, but not necessarily, getters are
access operations to extract values from Yasos objects (@pxref{Yasos}).
Several setters are predefined, corresponding to getters @code{car},
@code{cdr}, @code{string-ref} and @code{vector-ref} e.g., @code{(setter
car)} is equivalent to @code{set-car!}.

This implementation of setters is similar to that in Dylan(TM)
(@cite{Dylan: An object-oriented dynamic language}, Apple Computer
Eastern Research and Technology).  Common LISP provides similar
facilities through @code{setf}.

@defun setter getter
Returns the setter for the procedure @var{getter}.  E.g., since
@code{string-ref} is the getter corresponding to a setter which is
actually @code{string-set!}:
@example
(define foo "foo")
((setter string-ref) foo 0 #\F) ; set element 0 of foo
foo @result{} "Foo"
@end example
@end defun

@deffn Syntax set place new-value
If @var{place} is a variable name, @code{set} is equivalent to
@code{set!}.  Otherwise, @var{place} must have the form of a procedure
call, where the procedure name refers to a getter and the call indicates
an accessible generalized location, i.e., the call would return a value.
The return value of @code{set} is usually unspecified unless used with a
setter whose definition guarantees to return a useful value.
@example
(set (string-ref foo 2) #\O)  ; generalized location with getter
foo @result{} "FoO"
(set foo "foo")               ; like set!
foo @result{} "foo"
@end example
@end deffn

@deffn {Procedure} add-setter getter setter
Add procedures @var{getter} and @var{setter} to the (inaccessible) list
of valid setter/getter pairs.  @var{setter} implements the store
operation corresponding to the @var{getter} access operation for the
relevant state.  The return value is unspecified.
@end deffn

@deffn {Procedure} remove-setter-for getter
Removes the setter corresponding to the specified @var{getter} from the
list of valid setters.  The return value is unspecified.
@end deffn

@deffn Syntax define-access-operation getter-name
Shorthand for a Yasos @code{define-operation} defining an operation
@var{getter-name} that objects may support to return the value of some
mutable state.  The default operation is to signal an error.  The return
value is unspecified.
@end deffn


@node Yasos examples,  , Setters, Yasos
@subsection Examples

@lisp
;;; These definitions for PRINT and SIZE are
;;; already supplied by
(require 'yasos)

(define-operation (print obj port)
  (format port
          (if (instance? obj) "#<instance>" "~s")
          obj))

(define-operation (size obj)
  (cond
   ((vector? obj) (vector-length obj))
   ((list?   obj) (length obj))
   ((pair?   obj) 2)
   ((string? obj) (string-length obj))
   ((char?   obj) 1)
   (else
    (slib:error "Operation not supported: size" obj))))

(define-predicate cell?)
(define-operation (fetch obj))
(define-operation (store! obj newValue))

(define (make-cell value)
  (object
   ((cell? self) #t)
   ((fetch self) value)
   ((store! self newValue)
    (set! value newValue)
    newValue)
   ((size self) 1)
   ((print self port)
    (format port "#<Cell: ~s>" (fetch self)))))

(define-operation (discard obj value)
  (format #t "Discarding ~s~%" value))

(define (make-filtered-cell value filter)
  (object-with-ancestors
   ((cell (make-cell value)))
   ((store! self newValue)
   (if (filter newValue)
       (store! cell newValue)
       (discard self newValue)))))

(define-predicate array?)
(define-operation (array-ref array index))
(define-operation (array-set! array index value))

(define (make-array num-slots)
  (let ((anArray (make-vector num-slots)))
    (object
     ((array? self) #t)
     ((size self) num-slots)
     ((array-ref self index)
      (vector-ref  anArray index))
     ((array-set! self index newValue)
      (vector-set! anArray index newValue))
     ((print self port)
      (format port "#<Array ~s>" (size self))))))

(define-operation (position obj))
(define-operation (discarded-value obj))

(define (make-cell-with-history value filter size)
  (let ((pos 0) (most-recent-discard #f))
    (object-with-ancestors
     ((cell (make-filtered-call value filter))
      (sequence (make-array size)))
     ((array? self) #f)
     ((position self) pos)
     ((store! self newValue)
      (operate-as cell store! self newValue)
      (array-set! self pos newValue)
      (set! pos (+ pos 1)))
     ((discard self value)
      (set! most-recent-discard value))
     ((discarded-value self) most-recent-discard)
     ((print self port)
      (format port "#<Cell-with-history ~s>"
              (fetch self))))))

(define-access-operation fetch)
(add-setter fetch store!)
(define foo (make-cell 1))
(print foo #f)
@result{} "#<Cell: 1>"
(set (fetch foo) 2)
@result{}
(print foo #f)
@result{} "#<Cell: 2>"
(fetch foo)
@result{} 2
@end lisp


@node Textual Conversion Packages, Mathematical Packages, Scheme Syntax Extension Packages, Top
@chapter Textual Conversion Packages

@menu
* Precedence Parsing::          
* Format::                      Common-Lisp Format
* Standard Formatted I/O::      Posix printf and scanf
* Programs and Arguments::      
* HTML::                        Generating
* HTML Tables::                 Databases meet HTML
* HTTP and CGI::                Serve WWW sites
* Parsing HTML::                'html-for-each
* URI::                         Uniform Resource Identifier
* Parsing XML::                 'parse-xml or 'ssax
* Printing Scheme::             Nicely
* Time and Date::               
* NCBI-DNA::                    DNA and protein sequences
* Schmooz::                     Documentation markup for Scheme programs
@end menu

@node Precedence Parsing, Format, Textual Conversion Packages, Textual Conversion Packages
@section Precedence Parsing

@code{(require 'precedence-parse)} or @code{(require 'parse)}
@ftindex parse
@ftindex precedence

@noindent
This package implements:

@itemize @bullet
@item
a Pratt style precedence parser;
@item
a @dfn{tokenizer} which congeals tokens according to assigned classes of
constituent characters;
@item
procedures giving direct control of parser rulesets;
@item
procedures for higher level specification of rulesets.
@end itemize

@menu
* Precedence Parsing Overview::  
* Rule Types::                  
* Ruleset Definition and Use::  
* Token definition::            
* Nud and Led Definition::      
* Grammar Rule Definition::     
@end menu

@node Precedence Parsing Overview, Rule Types, Precedence Parsing, Precedence Parsing
@subsection Precedence Parsing Overview

@noindent
This package offers improvements over previous parsers.

@itemize @bullet
@item
Common computer language constructs are concisely specified.
@item
Grammars can be changed dynamically.  Operators can be assigned
different meanings within a lexical context.
@item
Rulesets don't need compilation.  Grammars can be changed incrementally.
@item
Operator precedence is specified by integers.
@item
All possibilities of bad input are handled @footnote{How do I know this?
I parsed 250kbyte of random input (an e-mail file) with a non-trivial
grammar utilizing all constructs.} and return as much structure as was
parsed when the error occured; The symbol @code{?} is substituted for
missing input.
@end itemize

@noindent
@cindex binding power
The notion of @dfn{binding power} may be unfamiliar to those
accustomed to BNF grammars.

@noindent
When two consecutive objects are parsed, the first might be the prefix
to the second, or the second might be a suffix of the first.
Comparing the left and right binding powers of the two objects decides
which way to interpret them.

@noindent
Objects at each level of syntactic grouping have binding powers.

@noindent
@cindex syntax tree
A syntax tree is not built unless the rules explicitly do so.  The
call graph of grammar rules effectively instantiate the sytnax tree.

@noindent
The JACAL symbolic math system
(@url{http://people.csail.mit.edu/jaffer/JACAL}) uses
@t{precedence-parse}.  Its grammar definitions in the file
@file{jacal/English.scm} can serve as examples of use.


@node Rule Types, Ruleset Definition and Use, Precedence Parsing Overview, Precedence Parsing
@subsection Rule Types

@noindent
Here are the higher-level syntax types and an example of each.
Precedence considerations are omitted for clarity.
See @ref{Grammar Rule Definition} for full details.
@deftp Grammar nofix bye exit
@example
bye
@end example
calls the function @code{exit} with no arguments.
@end deftp
@deftp Grammar prefix - negate
@example
- 42
@end example
Calls the function @code{negate} with the argument @code{42}.
@end deftp
@deftp Grammar infix - difference
@example
x - y
@end example
Calls the function @code{difference} with arguments @code{x} and @code{y}.
@end deftp
@deftp Grammar nary + sum
@example
x + y + z
@end example
Calls the function @code{sum} with arguments @code{x}, @code{y}, and
@code{y}.
@end deftp
@deftp Grammar postfix ! factorial
@example
5 !
@end example
Calls the function @code{factorial} with the argument @code{5}.
@end deftp
@deftp Grammar prestfix set set!
@example
set foo bar
@end example
Calls the function @code{set!} with the arguments @code{foo} and
@code{bar}.
@end deftp
@deftp Grammar commentfix /* */
@example
/* almost any text here */
@end example
Ignores the comment delimited by @code{/*} and @code{*/}.
@end deftp
@deftp Grammar matchfix @{ list @}
@example
@{0, 1, 2@}
@end example
Calls the function @code{list} with the arguments @code{0}, @code{1},
and @code{2}.
@end deftp
@deftp Grammar inmatchfix ( funcall )
@example
f(x, y)
@end example
Calls the function @code{funcall} with the arguments @code{f}, @code{x},
and @code{y}.
@end deftp
@deftp Grammar delim ;
@example
set foo bar;
@end example
delimits the extent of the restfix operator @code{set}.
@end deftp


@node Ruleset Definition and Use, Token definition, Rule Types, Precedence Parsing
@subsection Ruleset Definition and Use

@defvar *syn-defs*
A grammar is built by one or more calls to @code{prec:define-grammar}.
The rules are appended to @var{*syn-defs*}.  The value of
@var{*syn-defs*} is the grammar suitable for passing as an argument to
@code{prec:parse}.
@end defvar

@defvr Constant *syn-ignore-whitespace*
Is a nearly empty grammar with whitespace characters set to group 0,
which means they will not be made into tokens.  Most rulesets will want
to start with @code{*syn-ignore-whitespace*}
@end defvr

@noindent
In order to start defining a grammar, either

@example
(set! *syn-defs* '())
@end example
@noindent
or

@example
(set! *syn-defs* *syn-ignore-whitespace*)
@end example

@defun prec:define-grammar rule1 @dots{}
Appends @var{rule1} @dots{} to @var{*syn-defs*}.
@code{prec:define-grammar} is used to define both the character classes
and rules for tokens.
@end defun

@noindent
Once your grammar is defined, save the value of @code{*syn-defs*} in a
variable (for use when calling @code{prec:parse}).

@example
(define my-ruleset *syn-defs*)
@end example

@defun prec:parse ruleset delim column
@defunx prec:parse ruleset delim column port
The @var{ruleset} argument must be a list of rules as constructed by
@code{prec:define-grammar} and extracted from @var{*syn-defs*}.

The token @var{delim} may be a character, symbol, or string.  A
character @var{delim} argument will match only a character token;
i.e. a character for which no token-group is assigned.  A symbol or
string will match only a token string; i.e. a token resulting from a
token group.

@code{prec:parse} reads a @var{ruleset} grammar expression delimited
by @var{delim} from the given input @var{port}.  @code{prec:parse}
returns the next object parsable from the given input @var{port},
updating @var{port} to point to the first character past the end of the
external representation of the object.

For the purpose of reporting problems in error messages, this package
keeps track of the @dfn{current column}.  Its initial value is passed
as the third argument to @code{prec:parse}.

If an end of file is encountered in the input before any characters are
found that can begin an object, then an end of file object is returned.
If a delimiter (such as @var{delim}) is found before any characters are
found that can begin an object, then @code{#f} is returned.

The @var{port} argument may be omitted, in which case it defaults to the
value returned by @code{current-input-port}.  It is an error to parse
from a closed port.
@findex current-input-port
@end defun


@node Token definition, Nud and Led Definition, Ruleset Definition and Use, Precedence Parsing
@subsection Token definition

@defun tok:char-group group chars chars-proc
The argument @var{chars} may be a single character, a list of
characters, or a string.  Each character in @var{chars} is treated as
though @code{tok:char-group} was called with that character alone.

The argument @var{chars-proc} must be a procedure of one argument, a
list of characters.  After @code{tokenize} has finished
accumulating the characters for a token, it calls @var{chars-proc} with
the list of characters.  The value returned is the token which
@code{tokenize} returns.

The argument @var{group} may be an exact integer or a procedure of one
character argument.  The following discussion concerns the treatment
which the tokenizing routine, @code{tokenize}, will accord to characters
on the basis of their groups.

When @var{group} is a non-zero integer, characters whose group number is
equal to or exactly one less than @var{group} will continue to
accumulate.  Any other character causes the accumulation to stop (until
a new token is to be read).

The @var{group} of zero is special.  These characters are ignored when
parsed pending a token, and stop the accumulation of token characters
when the accumulation has already begun.  Whitespace characters are
usually put in group 0.

If @var{group} is a procedure, then, when triggerd by the occurence of
an initial (no accumulation) @var{chars} character, this procedure will
be repeatedly called with each successive character from the input
stream until the @var{group} procedure returns a non-false value.
@end defun

@noindent
The following convenient constants are provided for use with
@code{tok:char-group}.

@defvr Constant tok:decimal-digits
Is the string @code{"0123456789"}.
@end defvr
@defvr Constant tok:upper-case
Is the string consisting of all upper-case letters
("ABCDEFGHIJKLMNOPQRSTUVWXYZ").
@end defvr
@defvr Constant tok:lower-case
Is the string consisting of all lower-case letters
("abcdefghijklmnopqrstuvwxyz").
@end defvr
@defvr Constant tok:whitespaces
Is the string consisting of all characters between 0 and 255 for which
@code{char-whitespace?} returns true.
@end defvr


@node Nud and Led Definition, Grammar Rule Definition, Token definition, Precedence Parsing
@subsection Nud and Led Definition

This section describes advanced features.  You can skip this section on
first reading.

@noindent
The @dfn{Null Denotation} (or @dfn{nud})
@cindex Null Denotation, nud
of a token is the procedure and arguments applying for that token when
@dfn{Left}, an unclaimed parsed expression is not extant.

@noindent
The @dfn{Left Denotation} (or @dfn{led})
@cindex Left Denotation, led
of a token is the procedure, arguments, and lbp applying for that token
when there is a @dfn{Left}, an unclaimed parsed expression.

@noindent
In his paper,

@quotation
Pratt, V. R.
Top Down Operator Precendence.
@cite{SIGACT/SIGPLAN Symposium on Principles of Programming Languages},
Boston, 1973, pages 41-51
@end quotation

the @dfn{left binding power} (or @dfn{lbp}) was an independent property
of tokens.  I think this was done in order to allow tokens with NUDs but
not LEDs to also be used as delimiters, which was a problem for
statically defined syntaxes.  It turns out that @emph{dynamically
binding} NUDs and LEDs allows them independence.

@noindent
For the rule-defining procedures that follow, the variable @var{tk} may
be a character, string, or symbol, or a list composed of characters,
strings, and symbols.  Each element of @var{tk} is treated as though the
procedure were called for each element.

@noindent
Character @var{tk} arguments will match only character tokens;
i.e. characters for which no token-group is assigned.  Symbols and
strings will both match token strings; i.e. tokens resulting from token
groups.

@defun prec:make-nud tk sop arg1 @dots{}
Returns a rule specifying that @var{sop} be called when @var{tk} is
parsed.  If @var{sop} is a procedure, it is called with @var{tk} and
@var{arg1} @dots{} as its arguments; the resulting value is incorporated
into the expression being built.  Otherwise, @code{(list @var{sop}
@var{arg1} @dots{})} is incorporated.
@end defun

@noindent
If no NUD has been defined for a token; then if that token is a string,
it is converted to a symbol and returned; if not a string, the token is
returned.

@defun prec:make-led tk sop arg1 @dots{}
Returns a rule specifying that @var{sop} be called when @var{tk} is
parsed and @var{left} has an unclaimed parsed expression.  If @var{sop}
is a procedure, it is called with @var{left}, @var{tk}, and @var{arg1}
@dots{} as its arguments; the resulting value is incorporated into the
expression being built.  Otherwise, @var{left} is incorporated.
@end defun

@noindent
If no LED has been defined for a token, and @var{left} is set, the
parser issues a warning.

@node Grammar Rule Definition,  , Nud and Led Definition, Precedence Parsing
@subsection Grammar Rule Definition

@noindent
Here are procedures for defining rules for the syntax types introduced
in @ref{Precedence Parsing Overview}.

@noindent
For the rule-defining procedures that follow, the variable @var{tk} may
be a character, string, or symbol, or a list composed of characters,
strings, and symbols.  Each element of @var{tk} is treated as though the
procedure were called for each element.

@noindent
For procedures prec:delim, @dots{}, prec:prestfix, if the @var{sop}
argument is @code{#f}, then the token which triggered this rule is
converted to a symbol and returned.  A false @var{sop} argument to the
procedures prec:commentfix, prec:matchfix, or prec:inmatchfix has a
different meaning.

@noindent
Character @var{tk} arguments will match only character tokens;
i.e. characters for which no token-group is assigned.  Symbols and
strings will both match token strings; i.e. tokens resulting from token
groups.

@defun prec:delim tk
Returns a rule specifying that @var{tk} should not be returned from
parsing; i.e. @var{tk}'s function is purely syntactic.  The end-of-file
is always treated as a delimiter.
@end defun

@defun prec:nofix tk sop
Returns a rule specifying the following actions take place when @var{tk}
is parsed:
@itemize @bullet
@item
If @var{sop} is a procedure, it is called with no arguments; the
resulting value is incorporated into the expression being built.
Otherwise, the list of @var{sop} is incorporated.
@end itemize
@end defun

@defun prec:prefix tk sop bp rule1 @dots{}
Returns a rule specifying the following actions take place when @var{tk}
is parsed:
@itemize @bullet
@item
The rules @var{rule1} @dots{} augment and, in case of conflict, override
rules currently in effect.
@item
@code{prec:parse1} is called with binding-power @var{bp}.
@item
If @var{sop} is a procedure, it is called with the expression returned
from @code{prec:parse1}; the resulting value is incorporated into the
expression being built.  Otherwise, the list of @var{sop} and the
expression returned from @code{prec:parse1} is incorporated.
@item
The ruleset in effect before @var{tk} was parsed is restored;
@var{rule1} @dots{} are forgotten.
@end itemize
@end defun

@defun prec:infix tk sop lbp bp rule1 @dots{}
Returns a rule declaring the left-binding-precedence of the token
@var{tk} is @var{lbp} and specifying the following actions take place
when @var{tk} is parsed:
@itemize @bullet
@item
The rules @var{rule1} @dots{} augment and, in case of conflict, override
rules currently in effect.
@item
One expression is parsed with binding-power @var{lbp}.  If instead a
delimiter is encountered, a warning is issued.
@item
If @var{sop} is a procedure, it is applied to the list of @var{left} and
the parsed expression; the resulting value is incorporated into the
expression being built.  Otherwise, the list of @var{sop}, the
@var{left} expression, and the parsed expression is incorporated.
@item
The ruleset in effect before @var{tk} was parsed is restored;
@var{rule1} @dots{} are forgotten.
@end itemize
@end defun

@defun prec:nary tk sop bp
Returns a rule declaring the left-binding-precedence of the token
@var{tk} is @var{bp} and specifying the following actions take place
when @var{tk} is parsed:
@itemize @bullet
@item
Expressions are parsed with binding-power @var{bp} as far as they are
interleaved with the token @var{tk}.
@item
If @var{sop} is a procedure, it is applied to the list of @var{left} and
the parsed expressions; the resulting value is incorporated into the
expression being built.  Otherwise, the list of @var{sop}, the
@var{left} expression, and the parsed expressions is incorporated.
@end itemize
@end defun

@defun prec:postfix tk sop lbp
Returns a rule declaring the left-binding-precedence of the token
@var{tk} is @var{lbp} and specifying the following actions take place
when @var{tk} is parsed:
@itemize @bullet
@item
If @var{sop} is a procedure, it is called with the @var{left} expression;
the resulting value is incorporated into the expression being built.
Otherwise, the list of @var{sop} and the @var{left} expression is
incorporated.
@end itemize
@end defun

@defun prec:prestfix tk sop bp rule1 @dots{}
Returns a rule specifying the following actions take place when @var{tk}
is parsed:
@itemize @bullet
@item
The rules @var{rule1} @dots{} augment and, in case of conflict, override
rules currently in effect.
@item
Expressions are parsed with binding-power @var{bp} until a delimiter is
reached.
@item
If @var{sop} is a procedure, it is applied to the list of parsed
expressions; the resulting value is incorporated into the expression
being built.  Otherwise, the list of @var{sop} and the parsed
expressions is incorporated.
@item
The ruleset in effect before @var{tk} was parsed is restored;
@var{rule1} @dots{} are forgotten.
@end itemize
@end defun

@defun prec:commentfix tk stp match rule1 @dots{}
Returns rules specifying the following actions take place when @var{tk}
is parsed:
@itemize @bullet
@item
The rules @var{rule1} @dots{} augment and, in case of conflict, override
rules currently in effect.
@item
Characters are read until and end-of-file or a sequence of characters
is read which matches the @emph{string} @var{match}.
@item
If @var{stp} is a procedure, it is called with the string of all that
was read between the @var{tk} and @var{match} (exclusive).
@item
The ruleset in effect before @var{tk} was parsed is restored;
@var{rule1} @dots{} are forgotten.
@end itemize

Parsing of commentfix syntax differs from the others in several ways.
It reads directly from input without tokenizing; It calls @var{stp} but
does not return its value; nay any value.  I added the @var{stp}
argument so that comment text could be echoed.
@end defun

@defun prec:matchfix tk sop sep match rule1 @dots{}
Returns a rule specifying the following actions take place when @var{tk}
is parsed:
@itemize @bullet
@item
The rules @var{rule1} @dots{} augment and, in case of conflict, override
rules currently in effect.
@item
A rule declaring the token @var{match} a delimiter takes effect.
@item
Expressions are parsed with binding-power @code{0} until the token
@var{match} is reached.  If the token @var{sep} does not appear between
each pair of expressions parsed, a warning is issued.
@item
If @var{sop} is a procedure, it is applied to the list of parsed
expressions; the resulting value is incorporated into the expression
being built.  Otherwise, the list of @var{sop} and the parsed
expressions is incorporated.
@item
The ruleset in effect before @var{tk} was parsed is restored;
@var{rule1} @dots{} are forgotten.
@end itemize
@end defun

@defun prec:inmatchfix tk sop sep match lbp rule1 @dots{}
Returns a rule declaring the left-binding-precedence of the token
@var{tk} is @var{lbp} and specifying the following actions take place
when @var{tk} is parsed:
@itemize @bullet
@item
The rules @var{rule1} @dots{} augment and, in case of conflict, override
rules currently in effect.
@item
A rule declaring the token @var{match} a delimiter takes effect.
@item
Expressions are parsed with binding-power @code{0} until the token
@var{match} is reached.  If the token @var{sep} does not appear between
each pair of expressions parsed, a warning is issued.
@item
If @var{sop} is a procedure, it is applied to the list of @var{left} and
the parsed expressions; the resulting value is incorporated into the
expression being built.  Otherwise, the list of @var{sop}, the
@var{left} expression, and the parsed expressions is incorporated.
@item
The ruleset in effect before @var{tk} was parsed is restored;
@var{rule1} @dots{} are forgotten.
@end itemize
@end defun


@node Format, Standard Formatted I/O, Precedence Parsing, Textual Conversion Packages
@section Format (version 3.1)

@ifset html
<A NAME="format"></A>
@end ifset
@code{(require 'format)} or @code{(require 'srfi-28)}
@ftindex format

@c The @file{format.scm} package was removed because it was not
@c reentrant.  @url{http://people.csail.mit.edu/jaffer/SLIB.FAQ} explains
@c more about FORMAT's woes.

@include format.texi


@node Standard Formatted I/O, Programs and Arguments, Format, Textual Conversion Packages
@section Standard Formatted I/O

@menu
* Standard Formatted Output::   'printf
* Standard Formatted Input::    'scanf
@end menu

@subsection stdio

@code{(require 'stdio)}
@ftindex stdio

@code{require}s @code{printf} and @code{scanf} and additionally defines
the symbols:

@defvar stdin
Defined to be @code{(current-input-port)}.
@end defvar
@defvar stdout
Defined to be @code{(current-output-port)}.
@end defvar
@defvar stderr
Defined to be @code{(current-error-port)}.
@end defvar


@node Standard Formatted Output, Standard Formatted Input, Standard Formatted I/O, Standard Formatted I/O
@subsection Standard Formatted Output

@ifset html
<A NAME="printf"></A>
@end ifset
@code{(require 'printf)}
@ftindex printf

@deffn {Procedure} printf format arg1 @dots{}
@deffnx {Procedure} fprintf port format arg1 @dots{}
@deffnx {Procedure} sprintf str format arg1 @dots{}
@deffnx {Procedure} sprintf #f format arg1 @dots{}
@deffnx {Procedure} sprintf k format arg1 @dots{}

Each function converts, formats, and outputs its @var{arg1} @dots{}
arguments according to the control string @var{format} argument and
returns the number of characters output.

@code{printf} sends its output to the port @code{(current-output-port)}.
@code{fprintf} sends its output to the port @var{port}.  @code{sprintf}
@code{string-set!}s locations of the non-constant string argument
@var{str} to the output characters.

Two extensions of @code{sprintf} return new strings.  If the first
argument is @code{#f}, then the returned string's length is as many
characters as specified by the @var{format} and data; if the first
argument is a non-negative integer @var{k}, then the length of the
returned string is also bounded by @var{k}.

The string @var{format} contains plain characters which are copied to
the output stream, and conversion specifications, each of which results
in fetching zero or more of the arguments @var{arg1} @dots{}.  The
results are undefined if there are an insufficient number of arguments
for the format.  If @var{format} is exhausted while some of the
@var{arg1} @dots{} arguments remain unused, the excess @var{arg1}
@dots{} arguments are ignored.

The conversion specifications in a format string have the form:

@example
% @r{[} @var{flags} @r{]} @r{[} @var{width} @r{]} @r{[} . @var{precision} @r{]} @r{[} @var{type} @r{]} @var{conversion}
@end example

An output conversion specifications consist of an initial @samp{%}
character followed in sequence by:

@itemize @bullet
@item
Zero or more @dfn{flag characters} that modify the normal behavior of
the conversion specification.

@table @asis
@item @samp{-}
Left-justify the result in the field.  Normally the result is
right-justified.

@item @samp{+}
For the signed @samp{%d} and @samp{%i} conversions and all inexact
conversions, prefix a plus sign if the value is positive.

@item @samp{ }
For the signed @samp{%d} and @samp{%i} conversions, if the result
doesn't start with a plus or minus sign, prefix it with a space
character instead.  Since the @samp{+} flag ensures that the result
includes a sign, this flag is ignored if both are specified.

@item @samp{#}
For inexact conversions, @samp{#} specifies that the result should
always include a decimal point, even if no digits follow it.  For the
@samp{%g} and @samp{%G} conversions, this also forces trailing zeros
after the decimal point to be printed where they would otherwise be
elided.

For the @samp{%o} conversion, force the leading digit to be @samp{0}, as
if by increasing the precision.  For @samp{%x} or @samp{%X}, prefix a
leading @samp{0x} or @samp{0X} (respectively) to the result.  This
doesn't do anything useful for the @samp{%d}, @samp{%i}, or @samp{%u}
conversions.  Using this flag produces output which can be parsed by the
@code{scanf} functions with the @samp{%i} conversion
(@pxref{Standard Formatted Input}).


@item @samp{0}
Pad the field with zeros instead of spaces.  The zeros are placed after
any indication of sign or base.  This flag is ignored if the @samp{-}
flag is also specified, or if a precision is specified for an exact
converson.
@end table

@item
An optional decimal integer specifying the @dfn{minimum field width}.
If the normal conversion produces fewer characters than this, the field
is padded (with spaces or zeros per the @samp{0} flag) to the specified
width.  This is a @emph{minimum} width; if the normal conversion
produces more characters than this, the field is @emph{not} truncated.
@cindex minimum field width (@code{printf})

Alternatively, if the field width is @samp{*}, the next argument in the
argument list (before the actual value to be printed) is used as the
field width.  The width value must be an integer.  If the value is
negative it is as though the @samp{-} flag is set (see above) and the
absolute value is used as the field width.

@item
An optional @dfn{precision} to specify the number of digits to be
written for numeric conversions and the maximum field width for string
conversions.  The precision is specified by a period (@samp{.}) followed
optionally by a decimal integer (which defaults to zero if omitted).
@cindex precision (@code{printf})

Alternatively, if the precision is @samp{.*}, the next argument in the
argument list (before the actual value to be printed) is used as the
precision.  The value must be an integer, and is ignored if negative.
If you specify @samp{*} for both the field width and precision, the
field width argument precedes the precision argument.  The @samp{.*}
precision is an enhancement.  C library versions may not accept this
syntax.

For the @samp{%f}, @samp{%e}, and @samp{%E} conversions, the precision
specifies how many digits follow the decimal-point character.  The
default precision is @code{6}.  If the precision is explicitly @code{0},
the decimal point character is suppressed.

For the @samp{%g} and @samp{%G} conversions, the precision specifies how
many significant digits to print.  Significant digits are the first
digit before the decimal point, and all the digits after it.  If the
precision is @code{0} or not specified for @samp{%g} or @samp{%G}, it is
treated like a value of @code{1}.  If the value being printed cannot be
expressed accurately in the specified number of digits, the value is
rounded to the nearest number that fits.

For exact conversions, if a precision is supplied it specifies the
minimum number of digits to appear; leading zeros are produced if
necessary.  If a precision is not supplied, the number is printed with
as many digits as necessary.  Converting an exact @samp{0} with an
explicit precision of zero produces no characters.

@item
An optional one of @samp{l}, @samp{h} or @samp{L}, which is ignored for
numeric conversions.  It is an error to specify these modifiers for
non-numeric conversions.

@item
A character that specifies the conversion to be applied.
@end itemize

Exact Conversions

@table @asis
@item @samp{b}, @samp{B}
Print an integer as an unsigned binary number.

@emph{Note:} @samp{%b} and @samp{%B} are SLIB extensions.


@item @samp{d}, @samp{i}
Print an integer as a signed decimal number.  @samp{%d} and @samp{%i}
are synonymous for output, but are different when used with @code{scanf}
for input (@pxref{Standard Formatted Input}).

@item @samp{o}
Print an integer as an unsigned octal number.

@item @samp{u}
Print an integer as an unsigned decimal number.

@item @samp{x}, @samp{X}
Print an integer as an unsigned hexadecimal number.  @samp{%x} prints
using the digits @samp{0123456789abcdef}.  @samp{%X} prints using the
digits @samp{0123456789ABCDEF}.
@end table

Inexact Conversions

@table @asis
@item @samp{f}
Print a floating-point number in fixed-point notation.

@item @samp{e}, @samp{E}
Print a floating-point number in exponential notation.  @samp{%e} prints
@samp{e} between mantissa and exponont.  @samp{%E} prints @samp{E}
between mantissa and exponont.

@item @samp{g}, @samp{G}
Print a floating-point number in either fixed or exponential notation,
whichever is more appropriate for its magnitude.  Unless an @samp{#}
flag has been supplied, trailing zeros after a decimal point will be
stripped off.  @samp{%g} prints @samp{e} between mantissa and exponont.
@samp{%G} prints @samp{E} between mantissa and exponent.

@item @samp{k}, @samp{K}
Print a number like @samp{%g}, except that an SI prefix is output
after the number, which is scaled accordingly.  @samp{%K} outputs a
dot between number and prefix, @samp{%k} does not.

@end table

Other Conversions

@table @asis
@item @samp{c}
Print a single character.  The @samp{-} flag is the only one which can
be specified.  It is an error to specify a precision.

@item @samp{s}
Print a string.  The @samp{-} flag is the only one which can be
specified.  A precision specifies the maximum number of characters to
output; otherwise all characters in the string are output.

@item @samp{a}, @samp{A}
Print a scheme expression.  The @samp{-} flag left-justifies the output.
The @samp{#} flag specifies that strings and characters should be quoted
as by @code{write} (which can be read using @code{read}); otherwise,
output is as @code{display} prints.  A precision specifies the maximum
number of characters to output; otherwise as many characters as needed
are output.

@emph{Note:} @samp{%a} and @samp{%A} are SLIB extensions.

@c @item @samp{p}
@c Print the value of a pointer.

@c @item @samp{n}
@c Get the number of characters printed so far.  See @ref{Other Output Conversions}.
@c Note that this conversion specification never produces any output.

@c @item @samp{m}
@c Print the string corresponding to the value of @code{errno}.
@c (This is a GNU extension.)
@c @xref{Other Output Conversions}.

@item @samp{%}
Print a literal @samp{%} character.  No argument is consumed.  It is an
error to specify flags, field width, precision, or type modifiers with
@samp{%%}.
@end table
@end deffn


@node Standard Formatted Input,  , Standard Formatted Output, Standard Formatted I/O
@subsection Standard Formatted Input

@code{(require 'scanf)}
@ftindex scanf

@deffn Function scanf-read-list format
@deffnx Function scanf-read-list format port
@deffnx Function scanf-read-list format string
@end deffn

@defmac scanf format arg1 @dots{}
@defmacx fscanf port format arg1 @dots{}
@defmacx sscanf str format arg1 @dots{}

Each function reads characters, interpreting them according to the
control string @var{format} argument.

@code{scanf-read-list} returns a list of the items specified as far as
the input matches @var{format}.  @code{scanf}, @code{fscanf}, and
@code{sscanf} return the number of items successfully matched and
stored.  @code{scanf}, @code{fscanf}, and @code{sscanf} also set the
location corresponding to @var{arg1} @dots{} using the methods:

@table @asis
@item symbol
@code{set!}
@item car expression
@code{set-car!}
@item cdr expression
@code{set-cdr!}
@item vector-ref expression
@code{vector-set!}
@item substring expression
@code{substring-move-left!}
@end table

The argument to a @code{substring} expression in @var{arg1} @dots{} must
be a non-constant string.  Characters will be stored starting at the
position specified by the second argument to @code{substring}.  The
number of characters stored will be limited by either the position
specified by the third argument to @code{substring} or the length of the
matched string, whichever is less.

The control string, @var{format}, contains conversion specifications and
other characters used to direct interpretation of input sequences.  The
control string contains:

@itemize @bullet
@item White-space characters (blanks, tabs, newlines, or formfeeds)
that cause input to be read (and discarded) up to the next
non-white-space character.

@item An ordinary character (not @samp{%}) that must match the next
character of the input stream.

@item Conversion specifications, consisting of the character @samp{%}, an
optional assignment suppressing character @samp{*}, an optional
numerical maximum-field width, an optional @samp{l}, @samp{h} or
@samp{L} which is ignored, and a conversion code.

@c @item The conversion specification can alternatively be prefixed by
@c the character sequence @samp{%n$} instead of the character @samp{%},
@c where @var{n} is a decimal integer in the range.  The @samp{%n$}
@c construction indicates that the value of the next input field should be
@c placed in the @var{n}th place in the return list, rather than to the next
@c unused one.  The two forms of introducing a conversion specification,
@c @samp{%} and @samp{%n$}, must not be mixed within a single format string
@c with the following exception: Skip fields (see below) can be designated
@c as @samp{%*} or @samp{%n$*}.  In the latter case, @var{n} is ignored.

@end itemize

Unless the specification contains the @samp{n} conversion character
(described below), a conversion specification directs the conversion of
the next input field.  The result of a conversion specification is
returned in the position of the corresponding argument points, unless
@samp{*} indicates assignment suppression.  Assignment suppression
provides a way to describe an input field to be skipped.  An input field
is defined as a string of characters; it extends to the next
inappropriate character or until the field width, if specified, is
exhausted.

@quotation
@emph{Note:} This specification of format strings differs from the
@cite{ANSI C} and @cite{POSIX} specifications.  In SLIB, white space
before an input field is not skipped unless white space appears before
the conversion specification in the format string.  In order to write
format strings which work identically with @cite{ANSI C} and SLIB,
prepend whitespace to all conversion specifications except @samp{[} and
@samp{c}.
@end quotation

The conversion code indicates the interpretation of the input field; For
a suppressed field, no value is returned.  The following conversion
codes are legal:

@table @asis

@item @samp{%}
A single % is expected in the input at this point; no value is returned.

@item @samp{d}, @samp{D}
A decimal integer is expected.

@item @samp{u}, @samp{U}
An unsigned decimal integer is expected.

@item @samp{o}, @samp{O}
An octal integer is expected.

@item @samp{x}, @samp{X}
A hexadecimal integer is expected.

@item @samp{i}
An integer is expected.  Returns the value of the next input item,
interpreted according to C conventions; a leading @samp{0} implies
octal, a leading @samp{0x} implies hexadecimal; otherwise, decimal is
assumed.

@item @samp{n}
Returns the total number of bytes (including white space) read by
@code{scanf}.  No input is consumed by @code{%n}.

@item @samp{f}, @samp{F}, @samp{e}, @samp{E}, @samp{g}, @samp{G}
A floating-point number is expected.  The input format for
floating-point numbers is an optionally signed string of digits,
possibly containing a radix character @samp{.}, followed by an optional
exponent field consisting of an @samp{E} or an @samp{e}, followed by an
optional @samp{+}, @samp{-}, or space, followed by an integer.

@item @samp{c}, @samp{C}
@var{Width} characters are expected.  The normal skip-over-white-space
is suppressed in this case; to read the next non-space character, use
@samp{%1s}.  If a field width is given, a string is returned; up to the
indicated number of characters is read.

@item @samp{s}, @samp{S}
A character string is expected The input field is terminated by a
white-space character.  @code{scanf} cannot read a null string.

@item @samp{[}
Indicates string data and the normal skip-over-leading-white-space is
suppressed.  The left bracket is followed by a set of characters, called
the scanset, and a right bracket; the input field is the maximal
sequence of input characters consisting entirely of characters in the
scanset.  @samp{^}, when it appears as the first character in the
scanset, serves as a complement operator and redefines the scanset as
the set of all characters not contained in the remainder of the scanset
string.  Construction of the scanset follows certain conventions.  A
range of characters may be represented by the construct first-last,
enabling @samp{[0123456789]} to be expressed @samp{[0-9]}.  Using this
convention, first must be lexically less than or equal to last;
otherwise, the dash stands for itself.  The dash also stands for itself
when it is the first or the last character in the scanset.  To include
the right square bracket as an element of the scanset, it must appear as
the first character (possibly preceded by a @samp{^}) of the scanset, in
which case it will not be interpreted syntactically as the closing
bracket.  At least one character must match for this conversion to
succeed.
@end table

The @code{scanf} functions terminate their conversions at end-of-file,
at the end of the control string, or when an input character conflicts
with the control string.  In the latter case, the offending character is
left unread in the input stream.
@end defmac


@node Programs and Arguments, HTML, Standard Formatted I/O, Textual Conversion Packages
@section Program and Arguments

@menu
* Getopt::                      Command Line option parsing
* Command Line::                A command line reader for Scheme shells
* Parameter lists::             'parameters
* Getopt Parameter lists::      'getopt-parameters
* Filenames::                   'filename
* Batch::                       'batch
@end menu

@node Getopt, Command Line, Programs and Arguments, Programs and Arguments
@subsection Getopt

@code{(require 'getopt)}
@ftindex getopt

This routine implements Posix command line argument parsing.  Notice
that returning values through global variables means that @code{getopt}
is @emph{not} reentrant.

Obedience to Posix format for the @code{getopt} calls sows confusion.
Passing @var{argc} and @var{argv} as arguments while referencing
@var{optind} as a global variable leads to strange behavior,
especially when the calls to @code{getopt} are buried in other
procedures.

Even in C, @var{argc} can be derived from @var{argv}; what purpose
does it serve beyond providing an opportunity for
@var{argv}/@var{argc} mismatch?  Just such a mismatch existed for
years in a SLIB @code{getopt--} example.

I have removed the @var{argc} and @var{argv} arguments to getopt
procedures; and replaced them with a global variable:

@defvar *argv*
Define @var{*argv*} with a list of arguments before calling getopt
procedures.  If you don't want the first (0th) element to be ignored,
set @var{*optind*} to 0 (after requiring getopt).
@end defvar

@defvar *optind*
Is the index of the current element of the command line.  It is
initially one.  In order to parse a new command line or reparse an old
one, @var{*optind*} must be reset.
@end defvar

@defvar *optarg*
Is set by getopt to the (string) option-argument of the current option.
@end defvar

@defun getopt optstring
Returns the next option letter in @var{*argv*} (starting from
@code{(vector-ref argv *optind*)}) that matches a letter in
@var{optstring}.  @var{*argv*} is a vector or list of strings, the 0th
of which getopt usually ignores.  @var{optstring} is a string of
recognized option characters; if a character is followed by a colon,
the option takes an argument which may be immediately following it in
the string or in the next element of @var{*argv*}.

@var{*optind*} is the index of the next element of the @var{*argv*} vector
to be processed.  It is initialized to 1 by @file{getopt.scm}, and
@code{getopt} updates it when it finishes with each element of
@var{*argv*}.

@code{getopt} returns the next option character from @var{*argv*} that
matches a character in @var{optstring}, if there is one that matches.
If the option takes an argument, @code{getopt} sets the variable
@var{*optarg*} to the option-argument as follows:

@itemize @bullet
@item
If the option was the last character in the string pointed to by an
element of @var{*argv*}, then @var{*optarg*} contains the next element
of @var{*argv*}, and @var{*optind*} is incremented by 2.  If the
resulting value of @var{*optind*} is greater than or equal to
@code{(length @var{*argv*})}, this indicates a missing option
argument, and @code{getopt} returns an error indication.

@item
Otherwise, @var{*optarg*} is set to the string following the option
character in that element of @var{*argv*}, and @var{*optind*} is
incremented by 1.
@end itemize

If, when @code{getopt} is called, the string @code{(vector-ref argv
*optind*)} either does not begin with the character @code{#\-} or is
just @code{"-"}, @code{getopt} returns @code{#f} without changing
@var{*optind*}.  If @code{(vector-ref argv *optind*)} is the string
@code{"--"}, @code{getopt} returns @code{#f} after incrementing
@var{*optind*}.

If @code{getopt} encounters an option character that is not contained in
@var{optstring}, it returns the question-mark @code{#\?} character.  If
it detects a missing option argument, it returns the colon character
@code{#\:} if the first character of @var{optstring} was a colon, or a
question-mark character otherwise.  In either case, @code{getopt} sets
the variable @var{getopt:opt} to the option character that caused the
error.

The special option @code{"--"} can be used to delimit the end of the
options; @code{#f} is returned, and @code{"--"} is skipped.

RETURN VALUE

@code{getopt} returns the next option character specified on the command
line.  A colon @code{#\:} is returned if @code{getopt} detects a missing
argument and the first character of @var{optstring} was a colon
@code{#\:}.

A question-mark @code{#\?} is returned if @code{getopt} encounters an
option character not in @var{optstring} or detects a missing argument
and the first character of @var{optstring} was not a colon @code{#\:}.

Otherwise, @code{getopt} returns @code{#f} when all command line options
have been parsed.

Example:
@lisp
#! /usr/local/bin/scm
(require 'program-arguments)
(require 'getopt)
(define argv (program-arguments))
@ftindex getopt
@ftindex program-arguments

(define opts ":a:b:cd")
(let loop ((opt (getopt (length argv) argv opts)))
  (case opt
    ((#\a) (print "option a: " *optarg*))
    ((#\b) (print "option b: " *optarg*))
    ((#\c) (print "option c"))
    ((#\d) (print "option d"))
    ((#\?) (print "error" getopt:opt))
    ((#\:) (print "missing arg" getopt:opt))
    ((#f) (if (< *optind* (length argv))
              (print "argv[" *optind* "]="
                     (list-ref argv *optind*)))
          (set! *optind* (+ *optind* 1))))
  (if (< *optind* (length argv))
      (loop (getopt (length argv) argv opts))))

(slib:exit)
@end lisp
@end defun

@subsection Getopt---

@defun @code{getopt--} optstring
The procedure @code{getopt--} is an extended version of @code{getopt}
which parses @dfn{long option names} of the form
@samp{--hold-the-onions} and @samp{--verbosity-level=extreme}.
@w{@code{Getopt--}} behaves as @code{getopt} except for non-empty
options beginning with @samp{--}.

Options beginning with @samp{--} are returned as strings rather than
characters.  If a value is assigned (using @samp{=}) to a long option,
@code{*optarg*} is set to the value.  The @samp{=} and value are
not returned as part of the option string.

No information is passed to @code{getopt--} concerning which long
options should be accepted or whether such options can take arguments.
If a long option did not have an argument, @code{*optarg*} will be set
to @code{#f}.  The caller is responsible for detecting and reporting
errors.

@example
(define opts ":-:b:")
(define *argv* '("foo" "-b9" "--f1" "--2=" "--g3=35234.342" "--"))
(define *optind* 1)
(define *optarg* #f)
(require 'qp)
@ftindex qp
(do ((i 5 (+ -1 i)))
    ((zero? i))
  (let ((opt (getopt-- opts)))
    (print *optind* opt *optarg*)))
@print{}
2 #\b "9"
3 "f1" #f
4 "2" ""
5 "g3" "35234.342"
5 #f "35234.342"
@end example
@end defun


@node Command Line, Parameter lists, Getopt, Programs and Arguments
@subsection Command Line

@include comparse.txi


@node Parameter lists, Getopt Parameter lists, Command Line, Programs and Arguments
@subsection Parameter lists

@code{(require 'parameters)}
@ftindex parameters

@noindent
Arguments to procedures in scheme are distinguished from each other by
their position in the procedure call.  This can be confusing when a
procedure takes many arguments, many of which are not often used.

@noindent
A @dfn{parameter-list} is a way of passing named information to a
procedure.  Procedures are also defined to set unused parameters to
default values, check parameters, and combine parameter lists.

@noindent
A @var{parameter} has the form @code{(@r{parameter-name} @r{value1}
@dots{})}.  This format allows for more than one value per
parameter-name.

@noindent
A @var{parameter-list} is a list of @var{parameter}s, each with a
different @var{parameter-name}.

@deffn Function make-parameter-list parameter-names
Returns an empty parameter-list with slots for @var{parameter-names}.
@end deffn

@deffn Function parameter-list-ref parameter-list parameter-name
@var{parameter-name} must name a valid slot of @var{parameter-list}.
@code{parameter-list-ref} returns the value of parameter
@var{parameter-name} of @var{parameter-list}.
@end deffn

@deffn Function remove-parameter parameter-name parameter-list
Removes the parameter @var{parameter-name} from @var{parameter-list}.
@code{remove-parameter} does not alter the argument
@var{parameter-list}.

If there are more than one @var{parameter-name} parameters, an error is
signaled.
@end deffn

@deffn {Procedure} adjoin-parameters! parameter-list parameter1 @dots{}
Returns @var{parameter-list} with @var{parameter1} @dots{} merged in.
@end deffn

@deffn {Procedure} parameter-list-expand expanders parameter-list
@var{expanders} is a list of procedures whose order matches the order of
the @var{parameter-name}s in the call to @code{make-parameter-list}
which created @var{parameter-list}.  For each non-false element of
@var{expanders} that procedure is mapped over the corresponding
parameter value and the returned parameter lists are merged into
@var{parameter-list}.

This process is repeated until @var{parameter-list} stops growing.  The
value returned from @code{parameter-list-expand} is unspecified.
@end deffn

@deffn Function fill-empty-parameters defaulters parameter-list
@var{defaulters} is a list of procedures whose order matches the order
of the @var{parameter-name}s in the call to @code{make-parameter-list}
which created @var{parameter-list}.  @code{fill-empty-parameters}
returns a new parameter-list with each empty parameter replaced with the
list returned by calling the corresponding @var{defaulter} with
@var{parameter-list} as its argument.
@end deffn

@deffn Function check-parameters checks parameter-list
@var{checks} is a list of procedures whose order matches the order of
the @var{parameter-name}s in the call to @code{make-parameter-list}
which created @var{parameter-list}.

@code{check-parameters} returns @var{parameter-list} if each @var{check}
of the corresponding @var{parameter-list} returns non-false.  If some
@var{check} returns @code{#f} a warning is signaled.
@end deffn

@noindent
In the following procedures @var{arities} is a list of symbols.  The
elements of @code{arities} can be:

@table @code
@item single
Requires a single parameter.
@item optional
A single parameter or no parameter is acceptable.
@item boolean
A single boolean parameter or zero parameters is acceptable.
@item nary
Any number of parameters are acceptable.
@item nary1
One or more of parameters are acceptable.
@end table

@deffn Function parameter-list->arglist positions arities parameter-list
Returns @var{parameter-list} converted to an argument list.  Parameters
of @var{arity} type @code{single} and @code{boolean} are converted to
the single value associated with them.  The other @var{arity} types are
converted to lists of the value(s).

@var{positions} is a list of positive integers whose order matches the
order of the @var{parameter-name}s in the call to
@code{make-parameter-list} which created @var{parameter-list}.  The
integers specify in which argument position the corresponding parameter
should appear.
@end deffn


@node Getopt Parameter lists, Filenames, Parameter lists, Programs and Arguments
@subsection Getopt Parameter lists

@include getparam.txi


@node Filenames, Batch, Getopt Parameter lists, Programs and Arguments
@subsection Filenames

@ftindex glob
@include glob.txi


@node Batch,  , Filenames, Programs and Arguments
@subsection Batch

@code{(require 'batch)}
@ftindex batch

@noindent
The batch procedures provide a way to write and execute portable scripts
for a variety of operating systems.  Each @code{batch:} procedure takes
as its first argument a parameter-list (@pxref{Parameter lists}).  This
parameter-list argument @var{parms} contains named associations.  Batch
currently uses 2 of these:

@table @code
@item batch-port
The port on which to write lines of the batch file.
@item batch-dialect
The syntax of batch file to generate.  Currently supported are:
@itemize @bullet
@item
unix
@item
dos
@item
vms
@item
amigaos
@item
system
@item
*unknown*
@end itemize
@end table

@noindent
The @samp{batch} module uses 2 enhanced relational tables
(@pxref{Using Databases}) to store information linking the names of
@code{operating-system}s to @code{batch-dialect}es.

@defun batch:initialize! database
Defines @code{operating-system} and @code{batch-dialect} tables and adds
the domain @code{operating-system} to the enhanced relational database
@var{database}.
@end defun

@defvar *operating-system*
Is batch's best guess as to which operating-system it is running under.
@code{*operating-system*} is set to @code{(software-type)}
(@pxref{Configuration}) unless @code{(software-type)} is @code{unix},
in which case finer distinctions are made.
@end defvar

@defun batch:call-with-output-script parms file proc
@var{proc} should be a procedure of one argument.  If @var{file} is an
output-port, @code{batch:call-with-output-script} writes an appropriate
header to @var{file} and then calls @var{proc} with @var{file} as the
only argument.  If @var{file} is a string,
@code{batch:call-with-output-script} opens a output-file of name
@var{file}, writes an appropriate header to @var{file}, and then calls
@var{proc} with the newly opened port as the only argument.  Otherwise,
@code{batch:call-with-output-script} acts as if it was called with the
result of @code{(current-output-port)} as its third argument.
@end defun

@noindent
The rest of the @code{batch:} procedures write (or execute if
@code{batch-dialect} is @code{system}) commands to the batch port which
has been added to @var{parms} or @code{(copy-tree @var{parms})} by the
code:

@example
(adjoin-parameters! @var{parms} (list 'batch-port @var{port}))
@end example

@defun batch:command parms string1 string2 @dots{}
Calls @code{batch:try-command} (below) with arguments, but signals an
error if @code{batch:try-command} returns @code{#f}.
@end defun

@noindent
These functions return a non-false value if the command was successfully
translated into the batch dialect and @code{#f} if not.  In the case of
the @code{system} dialect, the value is non-false if the operation
suceeded.

@defun batch:try-command parms string1 string2 @dots{}
Writes a command to the @code{batch-port} in @var{parms} which executes
the program named @var{string1} with arguments @var{string2} @dots{}.
@end defun

@defun batch:try-chopped-command parms arg1 arg2 @dots{} list
breaks the last argument @var{list} into chunks small enough so that the
command:

@example
@var{arg1} @var{arg2} @dots{} @var{chunk}
@end example

fits withing the platform's maximum command-line length.

@code{batch:try-chopped-command} calls @code{batch:try-command} with the
command and returns non-false only if the commands all fit and
@code{batch:try-command} of each command line returned non-false.
@end defun

@defun batch:run-script parms string1 string2 @dots{}
Writes a command to the @code{batch-port} in @var{parms} which executes
the batch script named @var{string1} with arguments @var{string2}
@dots{}.

@emph{Note:} @code{batch:run-script} and @code{batch:try-command} are not the
same for some operating systems (VMS).
@end defun

@defun batch:comment parms line1 @dots{}
Writes comment lines @var{line1} @dots{} to the @code{batch-port} in
@var{parms}.
@end defun

@defun batch:lines->file parms file line1 @dots{}
Writes commands to the @code{batch-port} in @var{parms} which create a
file named @var{file} with contents @var{line1} @dots{}.
@end defun

@defun batch:delete-file parms file
Writes a command to the @code{batch-port} in @var{parms} which deletes
the file named @var{file}.
@end defun

@defun batch:rename-file parms old-name new-name
Writes a command to the @code{batch-port} in @var{parms} which renames
the file @var{old-name} to @var{new-name}.
@end defun

@noindent
In addition, batch provides some small utilities very useful for writing
scripts:

@defun truncate-up-to path char
@defunx truncate-up-to path string
@defunx truncate-up-to path charlist
@var{path} can be a string or a list of strings.  Returns @var{path}
sans any prefixes ending with a character of the second argument.  This
can be used to derive a filename moved locally from elsewhere.

@example
(truncate-up-to "/usr/local/lib/slib/batch.scm" "/")
@result{} "batch.scm"
@end example
@end defun

@defun string-join joiner string1 @dots{}
Returns a new string consisting of all the strings @var{string1} @dots{}
in order appended together with the string @var{joiner} between each
adjacent pair.
@end defun

@defun must-be-first list1 list2
Returns a new list consisting of the elements of @var{list2} ordered so
that if some elements of @var{list1} are @code{equal?} to elements of
@var{list2}, then those elements will appear first and in the order of
@var{list1}.
@end defun

@defun must-be-last list1 list2
Returns a new list consisting of the elements of @var{list1} ordered so
that if some elements of @var{list2} are @code{equal?} to elements of
@var{list1}, then those elements will appear last and in the order of
@var{list2}.
@end defun

@defun os->batch-dialect osname
Returns its best guess for the @code{batch-dialect} to be used for the
operating-system named @var{osname}.  @code{os->batch-dialect} uses the
tables added to @var{database} by @code{batch:initialize!}.
@end defun

@noindent
Here is an example of the use of most of batch's procedures:

@example
(require 'databases)
@ftindex databases
(require 'parameters)
@ftindex parameters
(require 'batch)
@ftindex batch
(require 'filename)
@ftindex filename

(define batch (create-database #f 'alist-table))
(batch:initialize! batch)

(define my-parameters
  (list (list 'batch-dialect (os->batch-dialect *operating-system*))
        (list 'operating-system *operating-system*)
        (list 'batch-port (current-output-port)))) ;gets filled in later

(batch:call-with-output-script
 my-parameters
 "my-batch"
 (lambda (batch-port)
   (adjoin-parameters! my-parameters (list 'batch-port batch-port))
   (and
    (batch:comment my-parameters
                   "================ Write file with C program.")
    (batch:rename-file my-parameters "hello.c" "hello.c~")
    (batch:lines->file my-parameters "hello.c"
                       "#include <stdio.h>"
                       "int main(int argc, char **argv)"
                       "@{"
                       "  printf(\"hello world\\n\");"
                       "  return 0;"
                       "@}" )
    (batch:command my-parameters "cc" "-c" "hello.c")
    (batch:command my-parameters "cc" "-o" "hello"
                  (replace-suffix "hello.c" ".c" ".o"))
    (batch:command my-parameters "hello")
    (batch:delete-file my-parameters "hello")
    (batch:delete-file my-parameters "hello.c")
    (batch:delete-file my-parameters "hello.o")
    (batch:delete-file my-parameters "my-batch")
    )))
@end example

@noindent
Produces the file @file{my-batch}:

@example
#! /bin/sh
# "my-batch" script created by SLIB/batch Sun Oct 31 18:24:10 1999
# ================ Write file with C program.
mv -f hello.c hello.c~
rm -f hello.c
echo '#include <stdio.h>'>>hello.c
echo 'int main(int argc, char **argv)'>>hello.c
echo '@{'>>hello.c
echo '  printf("hello world\n");'>>hello.c
echo '  return 0;'>>hello.c
echo '@}'>>hello.c
cc -c hello.c
cc -o hello hello.o
hello
rm -f hello
rm -f hello.c
rm -f hello.o
rm -f my-batch
@end example

@noindent
When run, @file{my-batch} prints:

@example
bash$ my-batch
mv: hello.c: No such file or directory
hello world
@end example


@node HTML, HTML Tables, Programs and Arguments, Textual Conversion Packages
@section HTML

@include htmlform.txi


@node HTML Tables, HTTP and CGI, HTML, Textual Conversion Packages
@section HTML Tables

@include db2html.txi


@node HTTP and CGI, Parsing HTML, HTML Tables, Textual Conversion Packages
@section HTTP and CGI

@include http-cgi.txi


@node Parsing HTML, URI, HTTP and CGI, Textual Conversion Packages
@section Parsing HTML

@include html4each.txi


@node URI, Parsing XML, Parsing HTML, Textual Conversion Packages
@section URI

@include uri.txi


@node Parsing XML, Printing Scheme, URI, Textual Conversion Packages
@section Parsing XML

@include xml-parse.txi


@node Printing Scheme, Time and Date, Parsing XML, Textual Conversion Packages
@section Printing Scheme

@menu
* Generic-Write::               'generic-write
* Object-To-String::            'object->string
* Pretty-Print::                'pretty-print, 'pprint-file
@end menu

@node Generic-Write, Object-To-String, Printing Scheme, Printing Scheme
@subsection Generic-Write

@code{(require 'generic-write)}
@ftindex generic-write

@code{generic-write} is a procedure that transforms a Scheme data value
(or Scheme program expression) into its textual representation and
prints it.  The interface to the procedure is sufficiently general to
easily implement other useful formatting procedures such as pretty
printing, output to a string and truncated output.

@deffn {Procedure} generic-write obj display? width output
@table @var
@item obj
Scheme data value to transform.
@item display?
Boolean, controls whether characters and strings are quoted.
@item width
Extended boolean, selects format:
@table @asis
@item #f
single line format
@item integer > 0
pretty-print (value = max nb of chars per line)
@end table
@item output
Procedure of 1 argument of string type, called repeatedly with
successive substrings of the textual representation.  This procedure can
return @code{#f} to stop the transformation.
@end table

The value returned by @code{generic-write} is undefined.

Examples:
@lisp
(write obj) @equiv{} (generic-write obj #f #f @var{display-string})
(display obj) @equiv{} (generic-write obj #t #f @var{display-string})
@end lisp
@noindent
where
@lisp
@var{display-string} @equiv{}
(lambda (s) (for-each write-char (string->list s)) #t)
@end lisp
@end deffn


@node Object-To-String, Pretty-Print, Generic-Write, Printing Scheme
@subsection Object-To-String

@code{(require 'object->string)}
@ftindex object->string

@include obj2str.txi


@node Pretty-Print,  , Object-To-String, Printing Scheme
@subsection Pretty-Print

@code{(require 'pretty-print)}
@ftindex pretty-print

@deffn {Procedure} pretty-print obj
@deffnx {Procedure} pretty-print obj port

@code{pretty-print}s @var{obj} on @var{port}.  If @var{port} is not
specified, @code{current-output-port} is used.

Example:
@example
@group
(pretty-print '((1 2 3 4 5) (6 7 8 9 10) (11 12 13 14 15)
                (16 17 18 19 20) (21 22 23 24 25)))
   @print{} ((1 2 3 4 5)
   @print{}  (6 7 8 9 10)
   @print{}  (11 12 13 14 15)
   @print{}  (16 17 18 19 20)
   @print{}  (21 22 23 24 25))
@end group
@end example
@end deffn

@deffn {Procedure} pretty-print->string obj
@deffnx {Procedure} pretty-print->string obj width

Returns the string of @var{obj} @code{pretty-print}ed in @var{width}
columns.  If @var{width} is not specified, @code{(output-port-width)} is
used.

Example:
@example
@group
(pretty-print->string '((1 2 3 4 5) (6 7 8 9 10) (11 12 13 14 15)
                        (16 17 18 19 20) (21 22 23 24 25)))
@result{}
"((1 2 3 4 5)
 (6 7 8 9 10)
 (11 12 13 14 15)
 (16 17 18 19 20)
 (21 22 23 24 25))
"
@end group
@group
(pretty-print->string '((1 2 3 4 5) (6 7 8 9 10) (11 12 13 14 15)
                        (16 17 18 19 20) (21 22 23 24 25))
                      16)
@result{}
"((1 2 3 4 5)
 (6 7 8 9 10)
 (11
  12
  13
  14
  15)
 (16
  17
  18
  19
  20)
 (21
  22
  23
  24
  25))
"
@end group
@end example
@end deffn


@code{(require 'pprint-file)}
@ftindex pprint-file

@deffn {Procedure} pprint-file infile
@deffnx {Procedure} pprint-file infile outfile
Pretty-prints all the code in @var{infile}.  If @var{outfile} is
specified, the output goes to @var{outfile}, otherwise it goes to
@code{(current-output-port)}.
@end deffn

@defun pprint-filter-file infile proc outfile
@defunx pprint-filter-file infile proc
@var{infile} is a port or a string naming an existing file.  Scheme
source code expressions and definitions are read from the port (or file)
and @var{proc} is applied to them sequentially.

@var{outfile} is a port or a string.  If no @var{outfile} is specified
then @code{current-output-port} is assumed.  These expanded expressions
are then @code{pretty-print}ed to this port.

Whitepsace and comments (introduced by @code{;}) which are not part of
scheme expressions are reproduced in the output.  This procedure does
not affect the values returned by @code{current-input-port},
@code{current-error-port}, and @code{current-output-port}.
@end defun

@code{pprint-filter-file} can be used to pre-compile macro-expansion and
thus can reduce loading time.  The following will write into
@file{exp-code.scm} the result of expanding all defmacros in
@file{code.scm}.
@lisp
(require 'pprint-file)
@ftindex pprint-file
(require 'defmacroexpand)
@ftindex defmacroexpand
(defmacro:load "my-macros.scm")
(pprint-filter-file "code.scm" defmacro:expand* "exp-code.scm")
@end lisp


@node Time and Date, NCBI-DNA, Printing Scheme, Textual Conversion Packages
@section Time and Date

@menu
* Time Zone::                   
* Posix Time::                  'posix-time
* Common-Lisp Time::            'common-lisp-time
* ISO 8601::                    'iso-8601
* Time Infrastructure::         'time-core
@end menu

@noindent
If @code{(provided? 'current-time)}:

@noindent
The procedures @code{current-time}, @code{difftime}, and
@code{offset-time} deal with a @dfn{calendar time} datatype
@cindex time
@cindex calendar time
which may or may not be disjoint from other Scheme datatypes.

@defun current-time
Returns the time since 00:00:00 GMT, January 1, 1970, measured in
seconds.  Note that the reference time is different from the reference
time for @code{get-universal-time} in @ref{Common-Lisp Time}.
@end defun

@defun difftime caltime1 caltime0
Returns the difference (number of seconds) between twe calendar times:
@var{caltime1} - @var{caltime0}.  @var{caltime0} may also be a number.
@end defun

@defun offset-time caltime offset
Returns the calendar time of @var{caltime} offset by @var{offset} number
of seconds @code{(+ caltime offset)}.
@end defun


@node Time Zone, Posix Time, Time and Date, Time and Date
@subsection Time Zone

(require 'time-zone)

@deftp {Data Format} TZ-string

POSIX standards specify several formats for encoding time-zone rules.

@table @t
@item :@i{<pathname>}
If the first character of @i{<pathname>} is @samp{/}, then
@i{<pathname>} specifies the absolute pathname of a tzfile(5) format
time-zone file.  Otherwise, @i{<pathname>} is interpreted as a pathname
within @var{tzfile:vicinity} (/usr/lib/zoneinfo/) naming a tzfile(5)
format time-zone file.
@item @i{<std>}@i{<offset>}
The string @i{<std>} consists of 3 or more alphabetic characters.
@i{<offset>} specifies the time difference from GMT.  The @i{<offset>}
is positive if the local time zone is west of the Prime Meridian and
negative if it is east.  @i{<offset>} can be the number of hours or
hours and minutes (and optionally seconds) separated by @samp{:}.  For
example, @code{-4:30}.
@item @i{<std>}@i{<offset>}@i{<dst>}
@i{<dst>} is the at least 3 alphabetic characters naming the local
daylight-savings-time.
@item @i{<std>}@i{<offset>}@i{<dst>}@i{<doffset>}
@i{<doffset>} specifies the offset from the Prime Meridian when
daylight-savings-time is in effect.
@end table

The non-tzfile formats can optionally be followed by transition times
specifying the day and time when a zone changes from standard to
daylight-savings and back again.

@table @t
@item ,@i{<date>}/@i{<time>},@i{<date>}/@i{<time>}
The @i{<time>}s are specified like the @i{<offset>}s above, except that
leading @samp{+} and @samp{-} are not allowed.

Each @i{<date>} has one of the formats:

@table @t
@item J@i{<day>}
specifies the Julian day with @i{<day>} between 1 and 365.  February 29
is never counted and cannot be referenced.
@item @i{<day>}
This specifies the Julian day with n between 0 and 365.  February 29 is
counted in leap years and can be specified.
@item M@i{<month>}.@i{<week>}.@i{<day>}
This specifies day @i{<day>} (0 <= @i{<day>} <= 6) of week @i{<week>} (1
<= @i{<week>} <= 5) of month @i{<month>} (1 <= @i{<month>} <= 12).  Week
1 is the first week in which day d occurs and week 5 is the last week in
which day @i{<day>} occurs.  Day 0 is a Sunday.
@end table
@end table

@end deftp

@deftp {Data Type} time-zone
is a datatype encoding how many hours from Greenwich Mean Time the local
time is, and the @dfn{Daylight Savings Time} rules for changing it.
@end deftp

@defun time-zone TZ-string
Creates and returns a time-zone object specified by the string
@var{TZ-string}.  If @code{time-zone} cannot interpret @var{TZ-string},
@code{#f} is returned.
@end defun

@defun tz:params caltime tz
@var{tz} is a time-zone object.  @code{tz:params} returns a list of
three items:
@enumerate 0
@item
An integer.  0 if standard time is in effect for timezone @var{tz} at
@var{caltime}; 1 if daylight savings time is in effect for timezone
@var{tz} at @var{caltime}.
@item
The number of seconds west of the Prime Meridian timezone @var{tz} is at
@var{caltime}.
@item
The name for timezone @var{tz} at @var{caltime}.
@end enumerate

@code{tz:params} is unaffected by the default timezone; inquiries can be
made of any timezone at any calendar time.

@end defun

@defun tz:std-offset tz
@var{tz} is a time-zone object.  @code{tz:std-offset} returns the
number of seconds west of the Prime Meridian timezone @var{tz} is.

@end defun

@noindent
The rest of these procedures and variables are provided for POSIX
compatability.  Because of shared state they are not thread-safe.

@defun tzset
Returns the default time-zone.
@end defun

@defun tzset tz
Sets (and returns) the default time-zone to @var{tz}.
@end defun

@defun tzset TZ-string
Sets (and returns) the default time-zone to that specified by
@var{TZ-string}.

@code{tzset} also sets the variables @var{*timezone*}, @var{daylight?},
and @var{tzname}.  This function is automatically called by the time
conversion procedures which depend on the time zone
(@pxref{Time and Date}).
@end defun

@defvar *timezone*
Contains the difference, in seconds, between Greenwich Mean Time and
local standard time (for example, in the U.S.  Eastern time zone (EST),
timezone is 5*60*60).  @code{*timezone*} is initialized by @code{tzset}.
@end defvar

@defvar daylight?
is @code{#t} if the default timezone has rules for @dfn{Daylight Savings
Time}.  @emph{Note:} @var{daylight?} does not tell you when Daylight
Savings Time is in effect, just that the default zone sometimes has
Daylight Savings Time.
@end defvar

@defvar tzname
is a vector of strings.  Index 0 has the abbreviation for the standard
timezone; If @var{daylight?}, then index 1 has the abbreviation for the
Daylight Savings timezone.
@end defvar


@node Posix Time, Common-Lisp Time, Time Zone, Time and Date
@subsection Posix Time

@example
(require 'posix-time)
@ftindex posix-time
@end example

@deftp {Data Type} {Calendar-Time}
@cindex calendar time
@cindex caltime
is a datatype encapsulating time.
@end deftp

@deftp {Data Type} {Coordinated Universal Time}
@cindex Coordinated Universal Time
@cindex UTC
(abbreviated @dfn{UTC}) is a vector of integers representing time:

@enumerate 0
@item
 seconds (0 - 61)
@item
 minutes (0 - 59)
@item
 hours since midnight (0 - 23)
@item
 day of month (1 - 31)
@item
 month (0 - 11).  Note difference from @code{decode-universal-time}.
@item
 the number of years since 1900.  Note difference from
@code{decode-universal-time}.
@item
 day of week (0 - 6)
@item
 day of year (0 - 365)
@item
 1 for daylight savings, 0 for regular time
@end enumerate
@end deftp

@defun gmtime caltime
Converts the calendar time @var{caltime} to UTC and returns it.
@end defun

@defun localtime caltime tz
Returns @var{caltime} converted to UTC relative to timezone @var{tz}.
@end defun

@defun localtime caltime
converts the calendar time @var{caltime} to a vector of integers
expressed relative to the user's time zone.  @code{localtime} sets the
variable @var{*timezone*} with the difference between Coordinated
Universal Time (UTC) and local standard time in seconds
(@pxref{Time Zone,tzset}).

@end defun

@defun gmktime univtime
Converts a vector of integers in GMT Coordinated Universal Time (UTC)
format to a calendar time.
@end defun

@defun mktime univtime
Converts a vector of integers in local Coordinated Universal Time (UTC)
format to a calendar time.
@end defun

@defun mktime univtime tz
Converts a vector of integers in Coordinated Universal Time (UTC) format
(relative to time-zone @var{tz})
to calendar time.
@end defun

@defun asctime univtime
Converts the vector of integers @var{caltime} in Coordinated
Universal Time (UTC) format into a string of the form
@code{"Wed Jun 30 21:49:08 1993"}.
@end defun

@defun gtime caltime
@defunx ctime caltime
@defunx ctime caltime tz
Equivalent to @code{(asctime (gmtime @var{caltime}))},
@code{(asctime (localtime @var{caltime}))}, and
@code{(asctime (localtime @var{caltime} @var{tz}))}, respectively.
@end defun


@node Common-Lisp Time, ISO 8601, Posix Time, Time and Date
@subsection Common-Lisp Time

@example
(require 'common-lisp-time)
@ftindex common-lisp-time
@end example

@defun get-decoded-time
Equivalent to @code{(decode-universal-time (get-universal-time))}.
@end defun

@defun get-universal-time
Returns the current time as @dfn{Universal Time}, number of seconds
since 00:00:00 Jan 1, 1900 GMT.  Note that the reference time is
different from @code{current-time}.
@end defun

@defun decode-universal-time univtime
Converts @var{univtime} to @dfn{Decoded Time} format.
Nine values are returned:
@enumerate 0
@item
 seconds (0 - 61)
@item
 minutes (0 - 59)
@item
 hours since midnight
@item
 day of month
@item
 month (1 - 12).  Note difference from @code{gmtime} and @code{localtime}.
@item
 year (A.D.).  Note difference from @code{gmtime} and @code{localtime}.
@item
 day of week (0 - 6)
@item
 #t for daylight savings, #f otherwise
@item
 hours west of GMT (-24 - +24)
@end enumerate

Notice that the values returned by @code{decode-universal-time} do not
match the arguments to @code{encode-universal-time}.
@end defun

@defun encode-universal-time second minute hour date month year
@defunx encode-universal-time second minute hour date month year time-zone
Converts the arguments in Decoded Time format to Universal Time format.
If @var{time-zone} is not specified, the returned time is adjusted for
daylight saving time.  Otherwise, no adjustment is performed.

Notice that the values returned by @code{decode-universal-time} do not
match the arguments to @code{encode-universal-time}.
@end defun

@node ISO 8601, Time Infrastructure, Common-Lisp Time, Time and Date
@subsection ISO 8601

@include iso8601.txi

@node Time Infrastructure,  , ISO 8601, Time and Date
@subsection Time Infrastructure

@code{(require 'time-core)}

@defun time:gmtime tm
@defunx time:invert decoder target
@defunx time:split t tm_isdst tm_gmtoff tm_zone
@end defun

@code{(require 'tzfile)}

@defun tzfile:read path
@end defun


@node NCBI-DNA, Schmooz, Time and Date, Textual Conversion Packages
@section NCBI-DNA

@include ncbi-dna.txi


@node Schmooz,  , NCBI-DNA, Textual Conversion Packages
@section Schmooz

@include schmooz.texi


@node Mathematical Packages, Database Packages, Textual Conversion Packages, Top
@chapter Mathematical Packages

@menu
* Bit-Twiddling::               'logical
* Modular Arithmetic::          'modular
* Irrational Integer Functions::  
* Irrational Real Functions::   
* Prime Numbers::               'factor
* Random Numbers::              'random
* Discrete Fourier Transform::  'dft
* Cyclic Checksum::             'crc
* Graphing::                    
* Solid Modeling::              VRML97
* Color::                       
* Root Finding::                'root
* Minimizing::                  'minimize
* The Limit::                   'limit
* Commutative Rings::           'commutative-ring
* Matrix Algebra::              'determinant
@end menu

@node Bit-Twiddling, Modular Arithmetic, Mathematical Packages, Mathematical Packages
@section Bit-Twiddling

@code{(require 'logical)} or @code{(require 'srfi-60)}
@ftindex logical
@ftindex srfi-60

@noindent
The bit-twiddling functions are made available through the use of the
@code{logical} package.  @code{logical} is loaded by inserting
@ftindex logical
@code{(require 'logical)} before the code that uses these functions.
These functions behave as though operating on integers in
two's-complement representation.

@subsection Bitwise Operations

@defun logand n1 @dots{}
@defunx bitwise-and n1 @dots{}
Returns the integer which is the bit-wise AND of the integer
arguments.

Example:
@lisp
(number->string (logand #b1100 #b1010) 2)
   @result{} "1000"
@end lisp
@end defun

@defun logior n1 @dots{}
@defunx bitwise-ior n1 @dots{}
Returns the integer which is the bit-wise OR of the integer arguments.

Example:
@lisp
(number->string (logior #b1100 #b1010) 2)
   @result{} "1110"
@end lisp
@end defun

@defun logxor n1 @dots{}
@defunx bitwise-xor n1 @dots{}
Returns the integer which is the bit-wise XOR of the integer
arguments.

Example:
@lisp
(number->string (logxor #b1100 #b1010) 2)
   @result{} "110"
@end lisp
@end defun

@defun lognot n
@defunx bitwise-not n
Returns the integer which is the one's-complement of the integer
argument.

Example:
@lisp
(number->string (lognot #b10000000) 2)
   @result{} "-10000001"
(number->string (lognot #b0) 2)
   @result{} "-1"
@end lisp
@end defun

@defun bitwise-if mask n0 n1
@defunx bitwise-merge mask n0 n1
Returns an integer composed of some bits from integer @var{n0} and some
from integer @var{n1}.  A bit of the result is taken from @var{n0} if the
corresponding bit of integer @var{mask} is 1 and from @var{n1} if that bit
of @var{mask} is 0.
@end defun

@defun logtest j k
@defunx any-bits-set? j k
@example
(logtest j k) @equiv{} (not (zero? (logand j k)))

(logtest #b0100 #b1011) @result{} #f
(logtest #b0100 #b0111) @result{} #t
@end example
@end defun


@subsection Integer Properties

@defun logcount n
Returns the number of bits in integer @var{n}.  If integer is positive,
the 1-bits in its binary representation are counted.  If negative, the
0-bits in its two's-complement binary representation are counted.  If 0,
0 is returned.

Example:
@lisp
(logcount #b10101010)
   @result{} 4
(logcount 0)
   @result{} 0
(logcount -2)
   @result{} 1
@end lisp
@end defun

@noindent
On @code{discuss@@r6rs.org} Ben Harris credits Simon Tatham with the
idea to have @code{bitwise-bit-count} return a negative count for
negative inputs.  Alan Bawden came up with the succinct invariant.

@defun bitwise-bit-count n
If @var{n} is non-negative, this procedure returns the number of 1
bits in the two's-complement representation of @var{n}.  Otherwise it
returns the result of the following computation:

@lisp
(bitwise-not (bitwise-bit-count (bitwise-not @var{n})))
@end lisp
@end defun


@defun integer-length n
Returns the number of bits neccessary to represent @var{n}.

Example:
@lisp
(integer-length #b10101010)
   @result{} 8
(integer-length 0)
   @result{} 0
(integer-length #b1111)
   @result{} 4
@end lisp
@end defun

@defun log2-binary-factors n
@defunx first-set-bit n
Returns the number of factors of two of integer @var{n}.  This value
is also the bit-index of the least-significant @samp{1} bit in
@var{n}.

@lisp
(require 'printf)
(do ((idx 0 (+ 1 idx)))
      ((> idx 16))
    (printf "%s(%3d) ==> %-5d %s(%2d) ==> %-5d\n"
            'log2-binary-factors
            (- idx) (log2-binary-factors (- idx))
            'log2-binary-factors
            idx (log2-binary-factors idx)))
@print{}
log2-binary-factors(  0) ==> -1    log2-binary-factors( 0) ==> -1   
log2-binary-factors( -1) ==> 0     log2-binary-factors( 1) ==> 0    
log2-binary-factors( -2) ==> 1     log2-binary-factors( 2) ==> 1    
log2-binary-factors( -3) ==> 0     log2-binary-factors( 3) ==> 0    
log2-binary-factors( -4) ==> 2     log2-binary-factors( 4) ==> 2    
log2-binary-factors( -5) ==> 0     log2-binary-factors( 5) ==> 0    
log2-binary-factors( -6) ==> 1     log2-binary-factors( 6) ==> 1    
log2-binary-factors( -7) ==> 0     log2-binary-factors( 7) ==> 0    
log2-binary-factors( -8) ==> 3     log2-binary-factors( 8) ==> 3    
log2-binary-factors( -9) ==> 0     log2-binary-factors( 9) ==> 0    
log2-binary-factors(-10) ==> 1     log2-binary-factors(10) ==> 1    
log2-binary-factors(-11) ==> 0     log2-binary-factors(11) ==> 0    
log2-binary-factors(-12) ==> 2     log2-binary-factors(12) ==> 2    
log2-binary-factors(-13) ==> 0     log2-binary-factors(13) ==> 0    
log2-binary-factors(-14) ==> 1     log2-binary-factors(14) ==> 1    
log2-binary-factors(-15) ==> 0     log2-binary-factors(15) ==> 0    
log2-binary-factors(-16) ==> 4     log2-binary-factors(16) ==> 4    
@end lisp
@end defun

@subsection Bit Within Word

@defun logbit? index n
@defunx bit-set? index n
@example
(logbit? index n) @equiv{} (logtest (expt 2 index) n)

(logbit? 0 #b1101) @result{} #t
(logbit? 1 #b1101) @result{} #f
(logbit? 2 #b1101) @result{} #t
(logbit? 3 #b1101) @result{} #t
(logbit? 4 #b1101) @result{} #f
@end example
@end defun

@defun copy-bit index from bit
Returns an integer the same as @var{from} except in the @var{index}th bit,
which is 1 if @var{bit} is @code{#t} and 0 if @var{bit} is @code{#f}.

Example:
@example
(number->string (copy-bit 0 0 #t) 2)       @result{} "1"
(number->string (copy-bit 2 0 #t) 2)       @result{} "100"
(number->string (copy-bit 2 #b1111 #f) 2)  @result{} "1011"
@end example
@end defun


@subsection Field of Bits

@defun bit-field n start end
Returns the integer composed of the @var{start} (inclusive) through
@var{end} (exclusive) bits of @var{n}.  The @var{start}th bit becomes
the 0-th bit in the result.

Example:
@lisp
(number->string (bit-field #b1101101010 0 4) 2)
   @result{} "1010"
(number->string (bit-field #b1101101010 4 9) 2)
   @result{} "10110"
@end lisp
@end defun

@defun copy-bit-field to from start end
Returns an integer the same as @var{to} except possibly in the
@var{start} (inclusive) through @var{end} (exclusive) bits, which are
the same as those of @var{from}.  The 0-th bit of @var{from} becomes the
@var{start}th bit of the result.

Example:
@example
(number->string (copy-bit-field #b1101101010 0 0 4) 2)
        @result{} "1101100000"
(number->string (copy-bit-field #b1101101010 -1 0 4) 2)
        @result{} "1101101111"
(number->string (copy-bit-field #b110100100010000 -1 5 9) 2)
        @result{} "110100111110000"
@end example
@end defun

@defun ash n count
@defunx arithmetic-shift n count
Returns an integer equivalent to
@code{(inexact->exact (floor (* @var{n} (expt 2 @var{count}))))}.

Example:
@lisp
(number->string (ash #b1 3) 2)
   @result{} "1000"
(number->string (ash #b1010 -1) 2)
   @result{} "101"
@end lisp
@end defun


@defun rotate-bit-field n count start end
Returns @var{n} with the bit-field from @var{start} to @var{end}
cyclically permuted by @var{count} bits towards high-order.

Example:
@lisp
(number->string (rotate-bit-field #b0100 3 0 4) 2)
    @result{} "10"
(number->string (rotate-bit-field #b0100 -1 0 4) 2)
    @result{} "10"
(number->string (rotate-bit-field #b110100100010000 -1 5 9) 2)
    @result{} "110100010010000"
(number->string (rotate-bit-field #b110100100010000 1 5 9) 2)
    @result{} "110100000110000"
@end lisp
@end defun

@defun reverse-bit-field n start end
Returns @var{n} with the order of bits @var{start} to @var{end}
reversed.

@example
(number->string (reverse-bit-field #xa7 0 8) 16)
  @result{} "e5"
@end example
@end defun


@subsection Bits as Booleans

@defun integer->list k len
@defunx integer->list k
@code{integer->list} returns a list of @var{len} booleans
corresponding to each bit of the non-negative integer @var{k}.  #t is
coded for each 1; #f for 0.  The @var{len} argument defaults to
@code{(integer-length @var{k})}.
@end defun

@defun list->integer list
@code{list->integer} returns an integer formed from the booleans in the
list @var{list}, which must be a list of booleans.  A 1 bit is coded for
each #t; a 0 bit for #f.

@example
(list->integer (integer->list @var{k}))  @result{}  @var{k}
@end example
@end defun

@defun booleans->integer bool1 @dots{}
Returns the integer coded by the @var{bool1} @dots{} arguments.
@end defun


@node Modular Arithmetic, Irrational Integer Functions, Bit-Twiddling, Mathematical Packages
@section Modular Arithmetic

@include modular.txi


@node Irrational Integer Functions, Irrational Real Functions, Modular Arithmetic, Mathematical Packages
@section Irrational Integer Functions

@include math-integer.txi


@node Irrational Real Functions, Prime Numbers, Irrational Integer Functions, Mathematical Packages
@section Irrational Real Functions

@code{(require 'math-real)}
@ftindex math-real

Although this package defines real and complex functions, it is safe
to load into an integer-only implementation; those functions will be
defined to #f.

@defun real-exp x
@defunx real-ln x
@defunx real-log y x
@defunx real-sin x
@defunx real-cos x
@defunx real-tan x
@defunx real-asin x
@defunx real-acos x
@defunx real-atan x
@defunx atan y x

These procedures are part of every implementation that supports
general real numbers; they compute the usual transcendental functions.
@samp{real-ln} computes the natural logarithm of @var{x};
@samp{real-log} computes the logarithm of @var{x} base @var{y}, which
is @code{(/ (real-ln x) (real-ln y))}.  If arguments @var{x} and
@var{y} are not both real; or if the correct result would not be real,
then these procedures signal an error.

@end defun


@defun real-sqrt x

For non-negative real @var{x} the result will be its positive square
root; otherwise an error will be signaled.

@end defun


@defun real-expt  x1 x2

Returns @var{x1} raised to the power @var{x2} if that result is a real
number; otherwise signals an error.

@code{(real-expt 0.0 @var{x2})}

@itemize @bullet
@item
returns 1.0 for @var{x2} equal to 0.0;
@item
returns 0.0 for positive real @var{x2};
@item
signals an error otherwise.
@end itemize

@end defun


@defun quo x1 x2
@defunx rem x1 x2
@defunx mod x1 x2

@var{x2} should be non-zero.

@example
    (quo @var{x1} @var{x2})                     ==> @var{n_q}
    (rem @var{x1} @var{x2})                     ==> @var{x_r}
    (mod @var{x1} @var{x2})                     ==> @var{x_m}
@end example

where @var{n_q} is @var{x1}/@var{x2} rounded towards zero,
0 < |@var{x_r}| < |@var{x2}|, 0 < |@var{x_m}| < |@var{x2}|, @var{x_r}
and @var{x_m} differ from @var{x1} by a multiple of @var{x2},
@var{x_r} has the same sign as @var{x1}, and @var{x_m} has the same
sign as @var{x2}.

From this we can conclude that for @var{x2} not equal to 0,

@example
     (= @var{x1} (+ (* @var{x2} (quo @var{x1} @var{x2}))
           (rem @var{x1} @var{x2})))
                                       ==>  #t
@end example

provided all numbers involved in that computation are exact.

@example
    (quo 2/3 1/5)                         ==>  3
    (mod 2/3 1/5)                         ==>  1/15

    (quo .666 1/5)                        ==>  3.0
    (mod .666 1/5)                        ==>  65.99999999999995e-3
@end example
@end defun


@defun ln @var{z}

These procedures are part of every implementation that supports
general real numbers.
@samp{Ln} computes the natural logarithm of @var{z}

In general, the mathematical function ln is multiply defined.  The
value of ln @var{z} is defined to be the one whose imaginary part lies
in the range from -pi (exclusive) to pi (inclusive).

@end defun


@defun abs  x

For real argument @var{x}, @samp{Abs} returns the absolute value of
@var{x}' otherwise it signals an error.

@format
@t{(abs -7)                               ==>  7
}
@end format

@end defun

@defun make-rectangular  x1 x2
@defunx make-polar  x3 x4

These procedures are part of every implementation that supports
general complex numbers.  Suppose @var{x1}, @var{x2}, @var{x3}, and
@var{x4} are real numbers and @var{z} is a complex number such that
 

@center  @var{z} = @var{x1} + @var{x2}@w{i} = @var{x3} . e^@w{i} @var{x4}

Then

@format
@t{(make-rectangular @var{x1} @var{x2})               ==> @var{z}
(make-polar @var{x3} @var{x4})                     ==> @var{z}
}
@end format

where -pi < x_angle <= pi with x_angle = @var{x4} + 2pi n
for some integer n.

If an argument is not real, then these procedures signal an error.

@end defun


@node Prime Numbers, Random Numbers, Irrational Real Functions, Mathematical Packages
@section Prime Numbers

@code{(require 'factor)}
@ftindex factor
@ftindex primes

@include factor.txi


@node Random Numbers, Discrete Fourier Transform, Prime Numbers, Mathematical Packages
@section Random Numbers

@cindex RNG
@cindex PRNG
A pseudo-random number generator is only as good as the tests it passes.
George Marsaglia of Florida State University developed a battery of
tests named @dfn{DIEHARD} (@url{http://stat.fsu.edu/~geo/diehard.html}).
@file{diehard.c} has a bug which the patch
@url{http://groups.csail.mit.edu/mac/ftpdir/users/jaffer/diehard.c.pat} corrects.

SLIB's PRNG generates 8 bits at a time.  With the degenerate seed
@samp{0}, the numbers generated pass DIEHARD; but when bits are
combined from sequential bytes, tests fail.  With the seed
@samp{http://swissnet.ai.mit.edu/~jaffer/SLIB.html}, all of those
tests pass.

@menu
* Exact Random Numbers::        'random
* Inexact Random Numbers::      'random-inexact
@end menu

@node Exact Random Numbers, Inexact Random Numbers, Random Numbers, Random Numbers
@subsection Exact Random Numbers

@include random.txi


@node Inexact Random Numbers,  , Exact Random Numbers, Random Numbers
@subsection Inexact Random Numbers

@include randinex.txi


@node Discrete Fourier Transform, Cyclic Checksum, Random Numbers, Mathematical Packages
@section Discrete Fourier Transform

@include dft.txi


@node Cyclic Checksum, Graphing, Discrete Fourier Transform, Mathematical Packages
@section Cyclic Checksum

@code{(require 'crc)}
@ftindex crc
@noindent
Cyclic Redundancy Checks using Galois field GF(2) polynomial
arithmetic are used for error detection in many data transmission
and storage applications.

@noindent
The generator polynomials for various CRC protocols are availble
from many sources.  But the polynomial is just one of many
parameters which must match in order for a CRC implementation to
interoperate with existing systems:

@itemize @bullet

@item
the byte-order and bit-order of the data stream;

@item
whether the CRC or its inverse is being calculated;

@item
the initial CRC value; and

@item
whether and where the CRC value is appended (inverted
or non-inverted) to the data stream.

@end itemize

@noindent
The performance of a particular CRC polynomial over packets of given
sizes varies widely.  In terms of the probability of undetected
errors, some uses of extant CRC polynomials are suboptimal by several
orders of magnitude.

@noindent
If you are considering CRC for a new application, consult the
following article to find the optimum CRC polynomial for your range of
data lengths:

@itemize @bullet
@item
Philip Koopman and Tridib Chakravarty,@*
``Cyclic Redundancy Code (CRC) Polynomial Selection For Embedded Networks'',@*
The International Conference on Dependable Systems and Networks, DSN-2004.@*
@end itemize

@exdent @url{http://www.ece.cmu.edu/~koopman/roses/dsn04/koopman04_crc_poly_embedded.pdf}

@noindent
There is even some controversy over the polynomials themselves.

@defvr Constant crc-32-polynomial
For CRC-32, http://www2.sis.pitt.edu/~jkabara/tele-2100/lect08.html
gives x^32+x^26+x^23+x^16+x^12+x^11+x^10+x^8+x^7+x^5+x^4+x^2+x^1+1.

But
http://www.cs.ncl.ac.uk/people/harry.whitfield/home.formal/CRCs.html,
http://duchon.umuc.edu/Web_Pages/duchon/99_f_cm435/ShiftRegister.htm,
http://spinroot.com/spin/Doc/Book91_PDF/ch3.pdf,
http://www.erg.abdn.ac.uk/users/gorry/course/dl-pages/crc.html,
http://www.rad.com/networks/1994/err_con/crc_most.htm, and
http://www.gpfn.sk.ca/~rhg/csc8550s02/crc.html,
http://www.nobugconsulting.ro/crc.php give
x^32+x^26+x^23+x^22+x^16+x^12+x^11+x^10+x^8+x^7+x^5+x^4+x^2+x+1.

SLIB @code{crc-32-polynomial} uses the latter definition.
@end defvr

@defvr Constant crc-ccitt-polynomial

http://www.math.grin.edu/~rebelsky/Courses/CS364/2000S/Outlines/outline.12.html,
http://duchon.umuc.edu/Web_Pages/duchon/99_f_cm435/ShiftRegister.htm,
http://www.cs.ncl.ac.uk/people/harry.whitfield/home.formal/CRCs.html,
http://www2.sis.pitt.edu/~jkabara/tele-2100/lect08.html, and
http://www.gpfn.sk.ca/~rhg/csc8550s02/crc.html give
CRC-CCITT: x^16+x^12+x^5+1.
@end defvr

@defvr Constant crc-16-polynomial

http://www.math.grin.edu/~rebelsky/Courses/CS364/2000S/Outlines/outline.12.html,
http://duchon.umuc.edu/Web_Pages/duchon/99_f_cm435/ShiftRegister.htm,
http://www.cs.ncl.ac.uk/people/harry.whitfield/home.formal/CRCs.html,
http://www.gpfn.sk.ca/~rhg/csc8550s02/crc.html, and
http://www.usb.org/developers/data/crcdes.pdf give
CRC-16: x^16+x^15+x^2+1.
@end defvr

@defvr Constant crc-12-polynomial

http://www.math.grin.edu/~rebelsky/Courses/CS364/2000S/Outlines/outline.12.html,
http://www.cs.ncl.ac.uk/people/harry.whitfield/home.formal/CRCs.html,
http://www.it.iitb.ac.in/it605/lectures/link/node4.html, and
http://spinroot.com/spin/Doc/Book91_PDF/ch3.pdf give
CRC-12: x^12+x^11+x^3+x^2+1.

But
http://www.ffldusoe.edu/Faculty/Denenberg/Topics/Networks/Error_Detection_Correction/crc.html,
http://duchon.umuc.edu/Web_Pages/duchon/99_f_cm435/ShiftRegister.htm,
http://www.eng.uwi.tt/depts/elec/staff/kimal/errorcc.html,
http://www.ee.uwa.edu.au/~roberto/teach/itc314/java/CRC/,
http://www.gpfn.sk.ca/~rhg/csc8550s02/crc.html, and
http://www.efg2.com/Lab/Mathematics/CRC.htm give
CRC-12: x^12+x^11+x^3+x^2+x+1.

These differ in bit 1 and calculations using them return different
values.  With citations near evenly split, it is hard to know which is
correct.  Thanks to Philip Koopman for breaking the tie in favor of
the latter (#xC07).
@end defvr

@defvr Constant crc-10-polynomial

http://www.math.grin.edu/~rebelsky/Courses/CS364/2000S/Outlines/outline.12.html gives
CRC-10: x^10+x^9+x^5+x^4+1;
but
http://cell-relay.indiana.edu/cell-relay/publications/software/CRC/crc10.html,
http://www.it.iitb.ac.in/it605/lectures/link/node4.html,
http://www.gpfn.sk.ca/~rhg/csc8550s02/crc.html,
http://www.techfest.com/networking/atm/atm.htm,
http://www.protocols.com/pbook/atmcell2.htm, and
http://www.nobugconsulting.ro/crc.php give
CRC-10: x^10+x^9+x^5+x^4+x+1.
@end defvr

@defvr Constant crc-08-polynomial

http://www.math.grin.edu/~rebelsky/Courses/CS364/2000S/Outlines/outline.12.html,
http://www.cs.ncl.ac.uk/people/harry.whitfield/home.formal/CRCs.html,
http://www.it.iitb.ac.in/it605/lectures/link/node4.html, and
http://www.nobugconsulting.ro/crc.php give
CRC-8: x^8+x^2+x^1+1
@end defvr

@defvr Constant atm-hec-polynomial

http://cell-relay.indiana.edu/cell-relay/publications/software/CRC/32bitCRC.tutorial.html and
http://www.gpfn.sk.ca/~rhg/csc8550s02/crc.html give
ATM HEC: x^8+x^2+x+1.
@end defvr

@defvr Constant dowcrc-polynomial

http://www.cs.ncl.ac.uk/people/harry.whitfield/home.formal/CRCs.html gives
DOWCRC: x^8+x^5+x^4+1.
@end defvr

@defvr Constant usb-token-polynomial

http://www.usb.org/developers/data/crcdes.pdf and
http://www.nobugconsulting.ro/crc.php give
USB-token: x^5+x^2+1.
@end defvr

@noindent
Each of these polynomial constants is a string of @samp{1}s and
@samp{0}s, the exponent of each power of @var{x} in descending order.

@defun crc:make-table poly

@var{poly} must be string of @samp{1}s and @samp{0}s beginning with
@samp{1} and having length greater than 8.  @code{crc:make-table}
returns a vector of 256 integers, such that:

@example
(set! @var{crc}
      (logxor (ash (logand (+ -1 (ash 1 (- @var{deg} 8))) @var{crc}) 8)
              (vector-ref @var{crc-table}
                          (logxor (ash @var{crc} (- 8 @var{deg})) @var{byte}))))
@end example

will compute the @var{crc} with the 8 additional bits in @var{byte};
where @var{crc} is the previous accumulated CRC value, @var{deg} is
the degree of @var{poly}, and @var{crc-table} is the vector returned
by @code{crc:make-table}.

If the implementation does not support @var{deg}-bit integers, then
@code{crc:make-table} returns #f.

@end defun


@defun cksum file

Computes the P1003.2/D11.2 (POSIX.2) 32-bit checksum of @var{file}.

@example
(require 'crc)
@ftindex crc
(cksum (in-vicinity (library-vicinity) "ratize.scm"))
@result{} 157103930
@end example
@end defun

@defun cksum port
Computes the checksum of the bytes read from @var{port} until the
end-of-file.

@end defun

@noindent
@cindex cksum-string
@code{cksum-string}, which returns the P1003.2/D11.2 (POSIX.2) 32-bit
checksum of the bytes in @var{str}, can be defined as follows:

@example
(require 'string-port)
(define (cksum-string str) (call-with-input-string str cksum))
@end example

@defun crc16 file

Computes the USB data-packet (16-bit) CRC of @var{file}.
@end defun

@defun crc16 port
Computes the USB data-packet (16-bit) CRC of the bytes read from
@var{port} until the end-of-file.

@code{crc16} calculates the same values as the crc16.pl program given
in http://www.usb.org/developers/data/crcdes.pdf.

@end defun

@defun crc5 file

Computes the USB token (5-bit) CRC of @var{file}.
@end defun

@defun crc5 port
Computes the USB token (5-bit) CRC of the bytes read from
@var{port} until the end-of-file.

@code{crc5} calculates the same values as the crc5.pl program given
in http://www.usb.org/developers/data/crcdes.pdf.

@end defun


@node Graphing, Solid Modeling, Cyclic Checksum, Mathematical Packages
@section Graphing

@menu
* Character Plotting::          
* PostScript Graphing::         
@end menu

@node Character Plotting, PostScript Graphing, Graphing, Graphing
@subsection Character Plotting

@code{(require 'charplot)}
@ftindex charplot

@defvar charplot:dimensions
A list of the maximum height (number of lines) and maximum width (number
of columns) for the graph, its scales, and labels.

The default value for @var{charplot:dimensions} is the
@code{output-port-height} and @code{output-port-width} of
@code{current-output-port}.
@end defvar

@deffn {Procedure} plot coords x-label y-label
@var{coords} is a list or vector of coordinates, lists of x and y
coordinates.  @var{x-label} and @var{y-label} are strings with which to
label the x and y axes.

Example:
@example
(require 'charplot)
@ftindex charplot
(set! charplot:dimensions '(20 55))

(define (make-points n)
  (if (zero? n)
      '()
      (cons (list (/ n 6) (sin (/ n 6))) (make-points (1- n)))))

(plot (make-points 40) "x" "Sin(x)")
@print{}
@group
  Sin(x)   _________________________________________
         1|-       ****                             |
          |      **    **                           |
      0.75|-    *        *                          |
          |    *          *                         |
       0.5|-  *            *                        |
          |  *                                     *|
      0.25|-                *                     * |
          | *                *                      |
         0|-------------------*------------------*--|
          |                                     *   |
     -0.25|-                   *               *    |
          |                     *             *     |
      -0.5|-                     *                  |
          |                       *          *      |
     -0.75|-                       *        *       |
          |                         **    **        |
        -1|-                          ****          |
          |:_____._____:_____._____:_____._____:____|
     x                 2           4           6
@end group
@end example
@end deffn

@deffn {Procedure} plot func x1 x2
@deffnx {Procedure} plot func x1 x2 npts
Plots the function of one argument @var{func} over the range @var{x1} to
@var{x2}.  If the optional integer argument @var{npts} is supplied, it
specifies the number of points to evaluate @var{func} at.

@example
(plot sin 0 (* 2 pi))
@print{}
@group
           _________________________________________
         1|-:       ****                            |
          | :     **    **                          |
      0.75|-:    *        *                         |
          | :   *          *                        |
       0.5|-:  **          **                       |
          | : *             *                       |
      0.25|-:**              **                     |
          | :*                *                     |
         0|-*------------------*--------------------|
          | :                  *                 *  |
     -0.25|-:                   **              **  |
          | :                    *             *    |
      -0.5|-:                     *           **    |
          | :                      *          *     |
     -0.75|-:                       *       **      |
          | :                        **    **       |
        -1|-:                          ****         |
          |_:_____._____:_____._____:_____._____:___|
            0           2           4           6
@end group
@end example
@end deffn

@deffn {Procedure} histograph data label
Creates and displays a histogram of the numerical values contained in
vector or list @var{data}

@example
(require 'random-inexact)
(histograph (do ((idx 99 (+ -1 idx))
                 (lst '() (cons (* .02 (random:normal)) lst)))
                ((negative? idx) lst))
            "normal")
@print{}
@group
           _________________________________________
         8|-                :    I                  |
          |                 :    I                  |
         7|-           I  I :    I                  |
          |            I  I :    I                  |
         6|-          III I :I   I                  |
          |           III I :I   I                  |
         5|-          IIIIIIIIII I                  |
          |           IIIIIIIIII I                  |
         4|-          IIIIIIIIIIII                  |
          |           IIIIIIIIIIII                  |
         3|-I    I I  IIIIIIIIIIII  II     I        |
          | I    I I  IIIIIIIIIIII  II     I        |
         2|-I    I I IIIIIIIIIIIIIIIII     I        |
          | I    I I IIIIIIIIIIIIIIIII     I        |
         1|-II I I IIIIIIIIIIIIIIIIIIIII   I I I    |
          | II I I IIIIIIIIIIIIIIIIIIIII   I I I    |
         0|-IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII----|
          |__.____:____.____:____.____:____.____:___|
  normal        -0.025      0       0.025      0.05
@end group
@end example
@end deffn


@node PostScript Graphing,  , Character Plotting, Graphing
@subsection PostScript Graphing

@include grapheps.txi


@node Solid Modeling, Color, Graphing, Mathematical Packages
@section Solid Modeling

@include solid.txi


@node Color, Root Finding, Solid Modeling, Mathematical Packages
@section Color

@ifset html
<A NAME="Color"></A>
@end ifset

@uref{http://people.csail.mit.edu/jaffer/Color}

@noindent
The goals of this package are to provide methods to specify, compute,
and transform colors in a core set of additive color spaces.  The color
spaces supported should be sufficient for working with the color data
encountered in practice and the literature.

@menu
* Color Data-Type::             'color
* Color Spaces::                XYZ, L*a*b*, L*u*v*, L*C*h, RGB709, sRGB
* Spectra::                     Color Temperatures and CIEXYZ(1931)
* Color Difference Metrics::    Society of Dyers and Colorists
* Color Conversions::           Low-level
* Color Names::                 in relational databases
* Daylight::                    Sunlight and sky colors
@end menu

@node Color Data-Type, Color Spaces, Color, Color
@subsection Color Data-Type

@ifset html
<A NAME="Color_Data-Type"></A>
@end ifset
@code{(require 'color)}

@defun color? obj
Returns #t if @var{obj} is a color.
@end defun

@defun color? obj typ
Returns #t if @var{obj} is a color of color-space @var{typ}.  The symbol
@var{typ} must be one of:

@itemize @bullet
@item
CIEXYZ
@item
RGB709
@item
L*a*b*
@item
L*u*v*
@item
sRGB
@item
e-sRGB
@item
L*C*h
@end itemize
@end defun

@defun make-color space arg @dots{}
Returns a color of type @var{space}.

@itemize @bullet
@item
For @var{space} arguments @code{CIEXYZ}, @code{RGB709}, and
@code{sRGB}, the sole @var{arg} is a list of three numbers.
@item
For @var{space} arguments @code{L*a*b*}, @code{L*u*v*}, and
@code{L*C*h}, @var{arg} is a list of three numbers optionally followed
by a whitepoint.
@item
For @code{xRGB}, @var{arg} is an integer.
@item
For @code{e-sRGB}, the arguments are as for @code{e-sRGB->color}.
@end itemize
@end defun

@defun color-space color
Returns the symbol for the color-space in which @var{color} is embedded.
@end defun

@defun color-precision color
For colors in digital color-spaces, @code{color-precision} returns the
number of bits used for each of the R, G, and B channels of the
encoding.  Otherwise, @code{color-precision} returns #f
@end defun

@defun color-white-point color
Returns the white-point of @var{color} in all color-spaces except CIEXYZ.
@end defun

@defun convert-color color space white-point
@defunx convert-color color space
@defunx convert-color color e-sRGB precision
Converts @var{color} into @var{space} at optional @var{white-point}.
@end defun

@subsubsection External Representation

@noindent
Each color encoding has an external, case-insensitive representation.
To ensure portability, the white-point for all color strings is D65.
@footnote{Readers may recognize these color string formats from Xlib.
X11's color management system was doomed by its fiction that CRT
monitors' (and X11 default) color-spaces were linear RGBi.  Unable to
shed this legacy, the only practical way to view pictures on X is to
ignore its color management system and use an sRGB monitor.  In this
implementation the device-independent RGB709 and sRGB spaces replace the
device-dependent RGBi and RGB spaces of Xlib.}

@multitable @columnfractions .33 .66
@item Color Space
@tab External Representation
@item CIEXYZ
@tab CIEXYZ:@i{<X>}/@i{<Y>}/@i{<Z>}
@item RGB709
@tab RGBi:@i{<R>}/@i{<G>}/@i{<B>}
@item L*a*b*
@tab CIELAB:@i{<L>}/@i{<a>}/@i{<b>}
@item L*u*v*
@tab CIELuv:@i{<L>}/@i{<u>}/@i{<v>}
@item L*C*h
@tab CIELCh:@i{<L>}/@i{<C>}/@i{<h>}
@end multitable

@noindent
The @var{X}, @var{Y}, @var{Z}, @var{L}, @var{a}, @var{b}, @var{u},
@var{v}, @var{C}, @var{h}, @var{R}, @var{G}, and @var{B} fields are
(Scheme) real numbers within the appropriate ranges.

@multitable @columnfractions .33 .66
@item Color Space
@tab External Representation
@item sRGB
@tab sRGB:@i{<R>}/@i{<G>}/@i{<B>}
@item e-sRGB10
@tab e-sRGB10:@i{<R>}/@i{<G>}/@i{<B>}
@item e-sRGB12
@tab e-sRGB12:@i{<R>}/@i{<G>}/@i{<B>}
@item e-sRGB16
@tab e-sRGB16:@i{<R>}/@i{<G>}/@i{<B>}
@end multitable

@noindent
The @var{R}, @var{G}, and @var{B}, fields are non-negative exact decimal
integers within the appropriate ranges.

@noindent
Several additional syntaxes are supported by @code{string->color}:

@multitable @columnfractions .33 .66
@item Color Space
@tab External Representation
@item sRGB
@tab sRGB:@i{<RRGGBB>}
@item sRGB
@tab #@i{<RRGGBB>}
@item sRGB
@tab 0x@i{<RRGGBB>}
@item sRGB
@tab #x@i{<RRGGBB>}
@end multitable

Where @var{RRGGBB} is a non-negative six-digit hexadecimal number.

@defun color->string color
Returns a string representation of @var{color}.
@end defun

@defun string->color string
Returns the color represented by @var{string}.  If @var{string} is not a
syntactically valid notation for a color, then @code{string->color}
returns #f.
@end defun

@subsubsection White

@noindent
We experience color relative to the illumination around us.
CIEXYZ coordinates, although subject to uniform scaling, are
objective.  Thus other color spaces are specified relative to a
@cindex white point
@dfn{white point} in CIEXYZ coordinates.
@cindex white point

@noindent
The white point for digital color spaces is set to D65.  For the other
spaces a @var{white-point} argument can be specified.  The default if
none is specified is the white-point with which the color was created
or last converted; and D65 if none has been specified.

@defvr Constant D65
Is the color of 6500.K (blackbody) illumination.  D65 is close
to the average color of daylight.
@end defvr

@defvr Constant D50
Is the color of 5000.K (blackbody) illumination.  D50 is the color of
indoor lighting by incandescent bulbs, whose filaments have
temperatures around 5000.K.
@end defvr


@node Color Spaces, Spectra, Color Data-Type, Color
@subsection Color Spaces

@ifset html
<A NAME="Color_Spaces"></A>
@end ifset
@include color.txi


@node Spectra, Color Difference Metrics, Color Spaces, Color
@subsection Spectra

@ifset html
<A NAME="Spectra"></A>
@end ifset
@noindent
The following functions compute colors from spectra, scale color
luminance, and extract chromaticity.  XYZ is used in the names of
procedures for unnormalized colors; the coordinates of CIEXYZ colors are
constrained as described in @ref{Color Spaces}.

@code{(require 'color-space)}

@noindent
A spectrum may be represented as:

@itemize @bullet
@item
A procedure of one argument accepting real numbers from 380e-9 to
780e-9, the wavelength in meters; or
@item
A vector of real numbers representing intensity samples evenly spaced
over some range of wavelengths overlapping the range 380e-9 to 780e-9.
@end itemize

@noindent
CIEXYZ values are calculated as dot-product with the X, Y (Luminance),
and Z @dfn{Spectral Tristimulus Values}.  The files @file{cie1931.xyz}
and @file{cie1964.xyz} in the distribution contain these CIE-defined
values.
@cindex Spectral Tristimulus Values

@deftp {Feature} cie1964
@ftindex cie1964
Loads the Spectral Tristimulus Values
@cite{CIE 1964 Supplementary Standard Colorimetric Observer},
defining @var{cie:x-bar}, @var{cie:y-bar}, and @var{cie:z-bar}.
@end deftp

@deftp {Feature} cie1931
@ftindex cie1931
Loads the Spectral Tristimulus Values
@cite{CIE 1931 Supplementary Standard Colorimetric Observer},
defining @var{cie:x-bar}, @var{cie:y-bar}, and @var{cie:z-bar}.
@end deftp

@deftp {Feature} ciexyz
@ftindex ciexyz
Requires Spectral Tristimulus Values, defaulting to cie1931,
defining @var{cie:x-bar}, @var{cie:y-bar}, and @var{cie:z-bar}.
@end deftp

@noindent
@code{(require 'cie1964)} or @code{(require 'cie1931)} will
@findex load-ciexyz
@code{load-ciexyz} specific values used by the following spectrum
conversion procedures.  The spectrum conversion procedures
@code{(require 'ciexyz)} to assure that a set is loaded.

@defun read-cie-illuminant path
@var{path} must be a string naming a file consisting of 107 numbers
for 5.nm intervals from 300.nm to 830.nm.  @code{read-cie-illuminant}
reads (using Scheme @code{read}) these numbers and returns a length
107 vector filled with them.
@end defun

@example
(define CIE:SI-D65
  (read-CIE-illuminant (in-vicinity (library-vicinity) "ciesid65.dat")))
(spectrum->XYZ CIE:SI-D65 300e-9 830e-9)
@result{} (25.108569422374994 26.418013465625001 28.764075683374993)
@end example


@defun read-normalized-illuminant path
@var{path} must be a string naming a file consisting of 107 numbers
for 5.nm intervals from 300.nm to 830.nm.
@code{read-normalized-illuminant} reads (using Scheme @code{read})
these numbers and returns a length 107 vector filled with them,
normalized so that @code{spectrum->XYZ} of the illuminant returns its
whitepoint.
@end defun

CIE Standard Illuminants A and D65 are included with SLIB:

@example
(define CIE:SI-A
  (read-normalized-illuminant (in-vicinity (library-vicinity) "ciesia.dat")))
(define CIE:SI-D65
  (read-normalized-illuminant (in-vicinity (library-vicinity) "ciesid65.dat")))
(spectrum->XYZ CIE:SI-A 300e-9 830e-9)
@result{} (1.098499460820401 999.9999999999998e-3 355.8173930654951e-3)
(CIEXYZ->sRGB (spectrum->XYZ CIE:SI-A 300e-9 830e-9))
@result{} (255 234 133)
(spectrum->XYZ CIE:SI-D65 300e-9 830e-9)
@result{} (950.4336673552745e-3 1.0000000000000002 1.0888053986649182)
(CIEXYZ->sRGB (spectrum->XYZ CIE:SI-D65 300e-9 830e-9))
@result{} (255 255 255)
@end example

@defun illuminant-map proc siv
@var{siv} must be a one-dimensional array or vector of 107 numbers.
@code{illuminant-map} returns a vector of length 107 containing the
result of applying @var{proc} to each element of @var{siv}.
@end defun

@defun illuminant-map->XYZ proc siv
@code{(spectrum->XYZ (illuminant-map @var{proc} @var{siv}) 300e-9 830e-9)}
@end defun

@defun spectrum->XYZ proc
@var{proc} must be a function of one argument.  @code{spectrum->XYZ}
computes the CIEXYZ(1931) values for the spectrum returned by @var{proc}
when called with arguments from 380e-9 to 780e-9, the wavelength in
meters.
@end defun

@defun spectrum->XYZ spectrum x1 x2
@var{x1} and @var{x2} must be positive real numbers specifying the
wavelengths (in meters) corresponding to the zeroth and last elements of
vector or list @var{spectrum}.  @code{spectrum->XYZ} returns the
CIEXYZ(1931) values for a light source with spectral values proportional
to the elements of @var{spectrum} at evenly spaced wavelengths between
@var{x1} and @var{x2}.

Compute the colors of 6500.K and 5000.K blackbody radiation:

@example
(require 'color-space)
(define xyz (spectrum->XYZ (blackbody-spectrum 6500)))
(define y_n (cadr xyz))
(map (lambda (x) (/ x y_n)) xyz)
    @result{} (0.9687111145512467 1.0 1.1210875945303613)

(define xyz (spectrum->XYZ (blackbody-spectrum 5000)))
(map (lambda (x) (/ x y_n)) xyz)
    @result{} (0.2933441826889158 0.2988931825387761 0.25783646831201573)
@end example
@end defun

@defun spectrum->chromaticity proc
@defunx spectrum->chromaticity spectrum x1 x2
Computes the chromaticity for the given spectrum.
@end defun

@defun wavelength->XYZ w
@var{w} must be a number between 380e-9 to 780e-9.
@code{wavelength->XYZ} returns (unnormalized) XYZ values for a
monochromatic light source with wavelength @var{w}.
@end defun

@defun wavelength->chromaticity w
@var{w} must be a number between 380e-9 to 780e-9.
@code{wavelength->chromaticity} returns the chromaticity for a
monochromatic light source with wavelength @var{w}.
@end defun

@defun blackbody-spectrum temp
@defunx blackbody-spectrum temp span
Returns a procedure of one argument (wavelength in meters), which
returns the radiance of a black body at @var{temp}.

The optional argument @var{span} is the wavelength analog of bandwidth.
With the default @var{span} of 1.nm (1e-9.m), the values returned by the
procedure correspond to the power of the photons with wavelengths
@var{w} to @var{w}+1e-9.
@end defun

@defun temperature->XYZ x
The positive number @var{x} is a temperature in degrees kelvin.
@code{temperature->XYZ} computes the unnormalized CIEXYZ(1931) values
for the spectrum of a black body at temperature @var{x}.

Compute the chromaticities of 6500.K and 5000.K blackbody radiation:

@example
(require 'color-space)
(XYZ->chromaticity (temperature->XYZ 6500))
    @result{} (0.3135191660557008 0.3236456786200268)

(XYZ->chromaticity (temperature->XYZ 5000))
    @result{} (0.34508082841161052 0.3516084965163377)
@end example
@end defun

@defun temperature->chromaticity x
The positive number @var{x} is a temperature in degrees kelvin.
@code{temperature->cromaticity} computes the chromaticity for the
spectrum of a black body at temperature @var{x}.

Compute the chromaticities of 6500.K and 5000.K blackbody radiation:

@example
(require 'color-space)
(temperature->chromaticity 6500)
    @result{} (0.3135191660557008 0.3236456786200268)

(temperature->chromaticity 5000)
    @result{} (0.34508082841161052 0.3516084965163377)
@end example
@end defun

@defun XYZ->chromaticity xyz
Returns a two element list: the x and y components of @var{xyz}
normalized to 1 (= @var{x} + @var{y} + @var{z}).
@end defun

@defun chromaticity->CIEXYZ x y
Returns the list of @var{x}, and @var{y}, 1 - @var{y} - @var{x}.
@end defun

@defun chromaticity->whitepoint x y
Returns the CIEXYZ(1931) values having luminosity 1 and chromaticity
@var{x} and @var{y}.
@end defun

@cindex xyY
@noindent
Many color datasets are expressed in @dfn{xyY} format; chromaticity with
CIE luminance (Y).  But xyY is not a CIE standard like CIEXYZ, CIELAB,
and CIELUV.  Although chrominance is well defined, the luminance
component is sometimes scaled to 1, sometimes to 100, but usually has no
obvious range.  With no given whitepoint, the only reasonable course is
to ascertain the luminance range of a dataset and normalize the values
to lie from 0 to 1.

@defun XYZ->xyY xyz
Returns a three element list: the @var{x} and @var{y} components of
@var{XYZ} normalized to 1, and CIE luminance @var{Y}.
@end defun

@defun xyY->XYZ xyY
@end defun

@defun xyY:normalize-colors colors
@var{colors} is a list of xyY triples.  @code{xyY:normalize-colors}
scales each chromaticity so it sums to 1 or less; and divides the
@var{Y} values by the maximum @var{Y} in the dataset, so all lie between
0 and 1.
@end defun

@defun xyY:normalize-colors colors n
If @var{n} is positive real, then @code{xyY:normalize-colors} divides
the @var{Y} values by @var{n} times the maximum @var{Y} in the dataset.

If @var{n} is an exact non-positive integer, then
@code{xyY:normalize-colors} divides the @var{Y} values by the maximum of
the @var{Y}s in the dataset excepting the -@var{n} largest @var{Y}
values.

In all cases, returned @var{Y} values are limited to lie from 0 to 1.
@end defun

@noindent
Why would one want to normalize to other than 1?  If the sun or its
reflection is the brightest object in a scene, then normalizing to its
luminance will tend to make the rest of the scene very dark.  As with
photographs, limiting the specular highlights looks better than
darkening everything else.

@noindent
The results of measurements being what they are,
@code{xyY:normalize-colors} is extremely tolerant.  Negative numbers are
replaced with zero, and chromaticities with sums greater than one are
scaled to sum to one.


@node Color Difference Metrics, Color Conversions, Spectra, Color
@subsection Color Difference Metrics

@ifset html
<A NAME="Color_Difference_Metrics"></A>
@end ifset

@code{(require 'color-space)}

The low-level metric functions operate on lists of 3 numbers, lab1,
lab2, lch1, or lch2.

@code{(require 'color)}

The wrapped functions operate on objects of type color, color1 and
color2 in the function entries.

@defun L*a*b*:DE* lab1 lab2
Returns the Euclidean distance between @var{lab1} and @var{lab2}.
@end defun

@defun CIE:DE* color1 color2 white-point
@defunx CIE:DE* color1 color2
Returns the Euclidean distance in L*a*b* space between @var{color1} and
@var{color2}.
@end defun


@defun L*a*b*:DE*94 lab1 lab2 parametric-factors
@defunx L*a*b*:DE*94 lab1 lab2

@defunx CIE:DE*94 color1 color2 parametric-factors
@defunx CIE:DE*94 color1 color2

Measures distance in the L*a*b* color-space.  The three axes are
individually scaled in their contributions to the total distance.

@code{DE*94} is not symmetrical in its arguments.  @var{lab1} is the
``reference'' color and @var{lab2} is the ``sample'' color.

The CIE has defined reference conditions under which the metric with
default parameters can be expected to perform well.  These are:

@itemize @bullet
@item
The specimens are homogeneous in colour.
@item
The colour difference (CIELAB) is <= 5 units.
@item
They are placed in direct edge contact.
@item
Each specimen subtends an angle of >4 degrees to the assessor, whose
colour vision is normal.
@item
They are illuminated at 1000 lux, and viewed against a background of
uniform grey, with L* of 50, under illumination simulating D65.
@end itemize

The @var{parametric-factors} argument is a list of 3 quantities kL, kC
and kH.  @var{parametric-factors} independently adjust each
colour-difference term to account for any deviations from the reference
viewing conditions.  Under the reference conditions explained above, the
default is kL = kC = kH = 1.
@end defun


@noindent
The Color Measurement Committee of The Society of Dyers and Colorists in
Great Britain created a more sophisticated color-distance function for
use in judging the consistency of dye lots.  With CMC:DE* it is possible
to use a single value pass/fail tolerance for all shades.

@defun CMC-DE lch1 lch2 parametric-factors
@defunx CMC-DE lch1 lch2 l c
@defunx CMC-DE lch1 lch2 l
@defunx CMC-DE lch1 lch2

@defunx CMC:DE* color1 color2 l c
@defunx CMC:DE* color1 color2

@code{CMC:DE} is a L*C*h metric.  The @var{parametric-factors}
argument is a list of 2 numbers @var{l} and @var{c}.  @var{l} and
@var{c} parameterize this metric.  1 and 1 are recommended for
perceptibility; the default, 2 and 1, for acceptability.
@end defun


@node Color Conversions, Color Names, Color Difference Metrics, Color
@subsection Color Conversions

@ifset html
<A NAME="Color_Conversions"></A>
@end ifset

@noindent
This package contains the low-level color conversion and color metric
routines operating on lists of 3 numbers.  There is no type or range
checking.

@code{(require 'color-space)}

@defvr Constant CIEXYZ:D65
Is the color of 6500.K (blackbody) illumination.  D65 is close to the
average color of daylight.
@end defvr

@defvr Constant CIEXYZ:D50
Is the color of 5000.K (blackbody) illumination.  D50 is the color of
indoor lighting by incandescent bulbs.
@end defvr

@defvr Constant CIEXYZ:A
@defvrx Constant CIEXYZ:B
@defvrx Constant CIEXYZ:C
@defvrx Constant CIEXYZ:E
CIE 1931 illuminants normalized to 1 = y.
@end defvr

@defun color:linear-transform matrix row
@end defun

@defun CIEXYZ->RGB709 xyz
@defunx RGB709->CIEXYZ srgb
@end defun

@defun CIEXYZ->L*u*v* xyz white-point
@defunx CIEXYZ->L*u*v* xyz
@defunx L*u*v*->CIEXYZ L*u*v* white-point
@defunx L*u*v*->CIEXYZ L*u*v*
The @var{white-point} defaults to CIEXYZ:D65.
@end defun

@defun CIEXYZ->L*a*b* xyz white-point
@defunx CIEXYZ->L*a*b* xyz
@defunx L*a*b*->CIEXYZ L*a*b* white-point
@defunx L*a*b*->CIEXYZ L*a*b*
The XYZ @var{white-point} defaults to CIEXYZ:D65.
@end defun

@defun L*a*b*->L*C*h L*a*b*
@defunx L*C*h->L*a*b* L*C*h
@end defun

@defun CIEXYZ->sRGB xyz
@defunx sRGB->CIEXYZ srgb
@end defun

@defun CIEXYZ->xRGB xyz
@defunx xRGB->CIEXYZ srgb
@end defun

@defun sRGB->xRGB xyz
@defunx xRGB->sRGB srgb
@end defun

@defun CIEXYZ->e-sRGB n xyz
@defunx e-sRGB->CIEXYZ n srgb
@end defun

@defun sRGB->e-sRGB n srgb
@defunx e-sRGB->sRGB n srgb
The integer @var{n} must be 10, 12, or 16.  Because sRGB and e-sRGB use
the same RGB709 chromaticities, conversion between them is simpler than
conversion through CIEXYZ.
@end defun

@noindent
Do not convert e-sRGB precision through @code{e-sRGB->sRGB} then
@code{sRGB->e-sRGB} -- values would be truncated to 8-bits!

@defun e-sRGB->e-sRGB n1 srgb n2
The integers @var{n1} and @var{n2} must be 10, 12, or 16.
@code{e-sRGB->e-sRGB} converts @var{srgb} to e-sRGB of precision
@var{n2}.
@end defun


@node Color Names, Daylight, Color Conversions, Color
@subsection Color Names

@ifset html
<A NAME="Color_Names"></A>
@end ifset
@include colornam.txi

@include mkclrnam.txi

@subsubheading The Short List

@code{(require 'saturate)}
@ftindex saturate

@defun saturate name
Looks for @var{name} among the 19 saturated colors from
@cite{Approximate Colors on CIE Chromaticity Diagram}:

@multitable @columnfractions .25 .25 .25 .25
@item reddish orange  @tab orange        @tab yellowish orange @tab yellow
@item greenish yellow @tab yellow green  @tab yellowish green  @tab green
@item bluish green    @tab blue green    @tab greenish blue    @tab blue
@item purplish blue   @tab bluish purple @tab purple           @tab reddish purple
@item red purple      @tab purplish red  @tab red
@end multitable

(@url{http://people.csail.mit.edu/jaffer/Color/saturate.pdf}).  If
@var{name} is found, the corresponding color is returned.  Otherwise #f
is returned.  Use saturate only for light source colors.
@end defun


@noindent
Resene Paints Limited, New Zealand's largest privately-owned and
operated paint manufacturing company, has generously made their
@cite{Resene RGB Values List} available.

@code{(require 'resene)}
@ftindex resene

@defun resene name
Looks for @var{name} among the 1300 entries in the Resene color-name
dictionary (@url{http://people.csail.mit.edu/jaffer/Color/resene.pdf}).
If @var{name} is found, the corresponding color is returned.  Otherwise
#f is returned.  The @cite{Resene RGB Values List} is an excellent
source for surface colors.
@end defun

@noindent
If you include the @dfn{Resene RGB Values List} in binary form in a
program, then you must include its license with your program:

@quotation
Resene RGB Values List@*
For further information refer to http://www.resene.co.nz@*
Copyright Resene Paints Ltd 2001

Permission to copy this dictionary, to modify it, to redistribute it,
to distribute modified versions, and to use it for any purpose is
granted, subject to the following restrictions and understandings.

@enumerate
@item
Any text copy made of this dictionary must include this copyright
notice in full.

@item
Any redistribution in binary form must reproduce this copyright
notice in the documentation or other materials provided with the
distribution.

@item
Resene Paints Ltd makes no warranty or representation that this
dictionary is error-free, and is under no obligation to provide any
services, by way of maintenance, update, or otherwise.

@item
There shall be no use of the name of Resene or Resene Paints Ltd
in any advertising, promotional, or sales literature without prior
written consent in each case.

@item
These RGB colour formulations may not be used to the detriment of
Resene Paints Ltd.
@end enumerate
@end quotation


@node Daylight,  , Color Names, Color
@subsection Daylight

@ifset html
<A NAME="Daylight"></A>
@end ifset
@include daylight.txi


@node Root Finding, Minimizing, Color, Mathematical Packages
@section Root Finding

@code{(require 'root)}
@ftindex root

In the Newton method, divide the @var{df/dx} argument by the
multiplicity of the desired root in order to preserve quadratic
convergence.

@defun newton:find-integer-root f df/dx x0
Given integer valued procedure @var{f}, its derivative (with respect to
its argument) @var{df/dx}, and initial integer value @var{x0} for which
@var{df/dx}(@var{x0}) is non-zero, returns an integer @var{x} for which
@var{f}(@var{x}) is closer to zero than either of the integers adjacent
to @var{x}; or returns @code{#f} if such an integer can't be found.

To find the closest integer to a given integer's square root:

@example
(define (integer-sqrt y)
  (newton:find-integer-root
   (lambda (x) (- (* x x) y))
   (lambda (x) (* 2 x))
   (ash 1 (quotient (integer-length y) 2))))

(integer-sqrt 15) @result{} 4
@end example
@end defun

@defun newton:find-root f df/dx x0 prec
Given real valued procedures @var{f}, @var{df/dx} of one (real)
argument, initial real value @var{x0} for which @var{df/dx}(@var{x0}) is
non-zero, and positive real number @var{prec}, returns a real @var{x}
for which @code{abs}(@var{f}(@var{x})) is less than @var{prec}; or
returns @code{#f} if such a real can't be found.

If @var{prec} is instead a negative integer, @code{newton:find-root}
returns the result of -@var{prec} iterations.
@end defun

@noindent
H. J. Orchard, @cite{The Laguerre Method for Finding the Zeros of
Polynomials}, IEEE Transactions on Circuits and Systems, Vol. 36,
No. 11, November 1989, pp 1377-1381.

@quotation
There are 2 errors in Orchard's Table II.  Line k=2 for starting
value of 1000+j0 should have Z_k of 1.0475 + j4.1036 and line k=2
for starting value of 0+j1000 should have Z_k of 1.0988 + j4.0833.
@end quotation


@defun laguerre:find-root f df/dz ddf/dz^2 z0 prec
Given complex valued procedure @var{f} of one (complex) argument, its
derivative (with respect to its argument) @var{df/dx}, its second
derivative @var{ddf/dz^2}, initial complex value @var{z0}, and positive
real number @var{prec}, returns a complex number @var{z} for which
@code{magnitude}(@var{f}(@var{z})) is less than @var{prec}; or returns
@code{#f} if such a number can't be found.

If @var{prec} is instead a negative integer, @code{laguerre:find-root}
returns the result of -@var{prec} iterations.
@end defun

@defun laguerre:find-polynomial-root deg f df/dz ddf/dz^2 z0 prec
Given polynomial procedure @var{f} of integer degree @var{deg} of one
argument, its derivative (with respect to its argument) @var{df/dx}, its
second derivative @var{ddf/dz^2}, initial complex value @var{z0}, and
positive real number @var{prec}, returns a complex number @var{z} for
which @code{magnitude}(@var{f}(@var{z})) is less than @var{prec}; or
returns @code{#f} if such a number can't be found.

If @var{prec} is instead a negative integer,
@code{laguerre:find-polynomial-root} returns the result of -@var{prec}
iterations.
@end defun

@defun secant:find-root f x0 x1 prec
@defunx secant:find-bracketed-root f x0 x1 prec
Given a real valued procedure @var{f} and two real valued starting
points @var{x0} and @var{x1}, returns a real @var{x} for which
@code{(abs (f x))} is less than @var{prec}; or returns
@code{#f} if such a real can't be found.

If @var{x0} and @var{x1} are chosen such that they bracket a root, that is
@example
(or (< (f x0) 0 (f x1))
    (< (f x1) 0 (f x0)))
@end example
then the root returned will be between @var{x0} and @var{x1}, and
@var{f} will not be passed an argument outside of that interval.

@code{secant:find-bracketed-root} will return @code{#f} unless @var{x0}
and @var{x1} bracket a root.

The secant method is used until a bracketing interval is found, at which point
a modified @i{regula falsi} method is used.

If @var{prec} is instead a negative integer, @code{secant:find-root}
returns the result of -@var{prec} iterations.

If @var{prec} is a procedure it should accept 5 arguments: @var{x0}
@var{f0} @var{x1} @var{f1} and @var{count}, where @var{f0} will be
@code{(f x0)}, @var{f1} @code{(f x1)}, and @var{count} the number of
iterations performed so far.  @var{prec} should return non-false
if the iteration should be stopped.
@end defun


@node Minimizing, The Limit, Root Finding, Mathematical Packages
@section Minimizing

@code{(require 'minimize)}
@ftindex minimize
@cindex minimize

@include minimize.txi


@node The Limit, Commutative Rings, Minimizing, Mathematical Packages
@section The Limit

@include limit.texi


@node Commutative Rings, Matrix Algebra, The Limit, Mathematical Packages
@section Commutative Rings

Scheme provides a consistent and capable set of numeric functions.
Inexacts implement a field; integers a commutative ring (and Euclidean
domain).  This package allows one to use basic Scheme numeric functions
with symbols and non-numeric elements of commutative rings.

@code{(require 'commutative-ring)}
@ftindex commutative-ring
@cindex ring, commutative

The @dfn{commutative-ring} package makes the procedures @code{+},
@code{-}, @code{*}, @code{/}, and @code{^} @dfn{careful} in the sense
@cindex careful
that any non-numeric arguments they do not reduce appear in the
expression output.  In order to see what working with this package is
like, self-set all the single letter identifiers (to their corresponding
symbols).
@cindex self-set

@example
(define a 'a)
@dots{}
(define z 'z)
@end example

Or just @code{(require 'self-set)}.  Now try some sample expressions:
@ftindex self-set

@example
(+ (+ a b) (- a b)) @result{} (* a 2)
(* (+ a b) (+ a b)) @result{} (^ (+ a b) 2)
(* (+ a b) (- a b)) @result{} (* (+ a b) (- a b))
(* (- a b) (- a b)) @result{} (^ (- a b) 2)
(* (- a b) (+ a b)) @result{} (* (+ a b) (- a b))
(/ (+ a b) (+ c d)) @result{} (/ (+ a b) (+ c d))
(^ (+ a b) 3) @result{} (^ (+ a b) 3)
(^ (+ a 2) 3) @result{} (^ (+ 2 a) 3)
@end example

Associative rules have been applied and repeated addition and
multiplication converted to multiplication and exponentiation.

We can enable distributive rules, thus expanding to sum of products
form:
@example
(set! *ruleset* (combined-rulesets distribute* distribute/))

(* (+ a b) (+ a b)) @result{} (+ (* 2 a b) (^ a 2) (^ b 2))
(* (+ a b) (- a b)) @result{} (- (^ a 2) (^ b 2))
(* (- a b) (- a b)) @result{} (- (+ (^ a 2) (^ b 2)) (* 2 a b))
(* (- a b) (+ a b)) @result{} (- (^ a 2) (^ b 2))
(/ (+ a b) (+ c d)) @result{} (+ (/ a (+ c d)) (/ b (+ c d)))
(/ (+ a b) (- c d)) @result{} (+ (/ a (- c d)) (/ b (- c d)))
(/ (- a b) (- c d)) @result{} (- (/ a (- c d)) (/ b (- c d)))
(/ (- a b) (+ c d)) @result{} (- (/ a (+ c d)) (/ b (+ c d)))
(^ (+ a b) 3) @result{} (+ (* 3 a (^ b 2)) (* 3 b (^ a 2)) (^ a 3) (^ b 3))
(^ (+ a 2) 3) @result{} (+ 8 (* a 12) (* (^ a 2) 6) (^ a 3))
@end example

Use of this package is not restricted to simple arithmetic expressions:

@example
(require 'determinant)

(determinant '((a b c) (d e f) (g h i))) @result{}
(- (+ (* a e i) (* b f g) (* c d h)) (* a f h) (* b d i) (* c e g))
@end example

Currently, only @code{+}, @code{-}, @code{*}, @code{/}, and @code{^}
support non-numeric elements.  Expressions with @code{-} are converted
to equivalent expressions without @code{-}, so behavior for @code{-} is
not defined separately.  @code{/} expressions are handled similarly.

This list might be extended to include @code{quotient}, @code{modulo},
@code{remainder}, @code{lcm}, and @code{gcd}; but these work only for
the more restrictive Euclidean (Unique Factorization) Domain.
@cindex Unique Factorization
@cindex Euclidean Domain

@section Rules and Rulesets

The @dfn{commutative-ring} package allows control of ring properties
through the use of @dfn{rulesets}.

@defvar *ruleset*
Contains the set of rules currently in effect.  Rules defined by
@code{cring:define-rule} are stored within the value of *ruleset* at the
time @code{cring:define-rule} is called.  If @var{*ruleset*} is
@code{#f}, then no rules apply.
@end defvar

@defun make-ruleset rule1 @dots{}
@defunx make-ruleset name rule1 @dots{}
Returns a new ruleset containing the rules formed by applying
@code{cring:define-rule} to each 4-element list argument @var{rule}.  If
the first argument to @code{make-ruleset} is a symbol, then the database
table created for the new ruleset will be named @var{name}.  Calling
@code{make-ruleset} with no rule arguments creates an empty ruleset.
@end defun

@defun combined-rulesets ruleset1 @dots{}
@defunx combined-rulesets name ruleset1 @dots{}
Returns a new ruleset containing the rules contained in each ruleset
argument @var{ruleset}.  If the first argument to
@code{combined-ruleset} is a symbol, then the database table created for
the new ruleset will be named @var{name}.  Calling
@code{combined-ruleset} with no ruleset arguments creates an empty
ruleset.
@end defun

Two rulesets are defined by this package.

@defvr Constant distribute*
Contains the ruleset to distribute multiplication over addition and
subtraction.
@end defvr

@defvr Constant distribute/
Contains the ruleset to distribute division over addition and
subtraction.

Take care when using both @var{distribute*} and @var{distribute/}
simultaneously.  It is possible to put @code{/} into an infinite loop.
@end defvr

You can specify how sum and product expressions containing non-numeric
elements simplify by specifying the rules for @code{+} or @code{*} for
cases where expressions involving objects reduce to numbers or to
expressions involving different non-numeric elements.

@defun cring:define-rule op sub-op1 sub-op2 reduction
Defines a rule for the case when the operation represented by symbol
@var{op} is applied to lists whose @code{car}s are @var{sub-op1} and
@var{sub-op2}, respectively.  The argument @var{reduction} is a
procedure accepting 2 arguments which will be lists whose @code{car}s
are @var{sub-op1} and @var{sub-op2}.
@end defun

@defun cring:define-rule op sub-op1 'identity reduction
Defines a rule for the case when the operation represented by symbol
@var{op} is applied to a list whose @code{car} is @var{sub-op1}, and
some other argument.  @var{Reduction} will be called with the list whose
@code{car} is @var{sub-op1} and some other argument.

If @var{reduction} returns @code{#f}, the reduction has failed and other
reductions will be tried.  If @var{reduction} returns a non-false value,
that value will replace the two arguments in arithmetic (@code{+},
@code{-}, and @code{*}) calculations involving non-numeric elements.

The operations @code{+} and @code{*} are assumed commutative; hence both
orders of arguments to @var{reduction} will be tried if necessary.

The following rule is the definition for distributing @code{*} over
@code{+}.

@example
(cring:define-rule
 '* '+ 'identity
 (lambda (exp1 exp2)
   (apply + (map (lambda (trm) (* trm exp2)) (cdr exp1))))))
@end example
@end defun

@section How to Create a Commutative Ring

The first step in creating your commutative ring is to write procedures
to create elements of the ring.  A non-numeric element of the ring must
be represented as a list whose first element is a symbol or string.
This first element identifies the type of the object.  A convenient and
clear convention is to make the type-identifying element be the same
symbol whose top-level value is the procedure to create it.

@example
(define (n . list1)
  (cond ((and (= 2 (length list1))
              (eq? (car list1) (cadr list1)))
         0)
        ((not (term< (first list1) (last1 list1)))
         (apply n (reverse list1)))
        (else (cons 'n list1))))

(define (s x y) (n x y))

(define (m . list1)
  (cond ((neq? (first list1) (term_min list1))
         (apply m (cyclicrotate list1)))
        ((term< (last1 list1) (cadr list1))
         (apply m (reverse (cyclicrotate list1))))
        (else (cons 'm list1))))
@end example

Define a procedure to multiply 2 non-numeric elements of the ring.
Other multiplicatons are handled automatically.  Objects for which rules
have @emph{not} been defined are not changed.

@example
(define (n*n ni nj)
  (let ((list1 (cdr ni)) (list2 (cdr nj)))
    (cond ((null? (intersection list1 list2)) #f)
          ((and (eq? (last1 list1) (first list2))
                (neq? (first list1) (last1 list2)))
           (apply n (splice list1 list2)))
          ((and (eq? (first list1) (first list2))
                (neq? (last1 list1) (last1 list2)))
           (apply n (splice (reverse list1) list2)))
          ((and (eq? (last1 list1) (last1 list2))
                (neq? (first list1) (first list2)))
           (apply n (splice list1 (reverse list2))))
          ((and (eq? (last1 list1) (first list2))
                (eq? (first list1) (last1 list2)))
           (apply m (cyclicsplice list1 list2)))
          ((and (eq? (first list1) (first list2))
                (eq? (last1 list1) (last1 list2)))
           (apply m (cyclicsplice (reverse list1) list2)))
          (else #f))))
@end example

Test the procedures to see if they work.

@example
;;; where cyclicrotate(list) is cyclic rotation of the list one step
;;; by putting the first element at the end
(define (cyclicrotate list1)
  (append (rest list1) (list (first list1))))
;;; and where term_min(list) is the element of the list which is
;;; first in the term ordering.
(define (term_min list1)
  (car (sort list1 term<)))
(define (term< sym1 sym2)
  (string<? (symbol->string sym1) (symbol->string sym2)))
(define first car)
(define rest cdr)
(define (last1 list1) (car (last-pair list1)))
(define (neq? obj1 obj2) (not (eq? obj1 obj2)))
;;; where splice is the concatenation of list1 and list2 except that their
;;; common element is not repeated.
(define (splice list1 list2)
  (cond ((eq? (last1 list1) (first list2))
         (append list1 (cdr list2)))
        (else (slib:error 'splice list1 list2))))
;;; where cyclicsplice is the result of leaving off the last element of
;;; splice(list1,list2).
(define (cyclicsplice list1 list2)
  (cond ((and (eq? (last1 list1) (first list2))
              (eq? (first list1) (last1 list2)))
         (butlast (splice list1 list2) 1))
        (else (slib:error 'cyclicsplice list1 list2))))

(N*N (S a b) (S a b)) @result{} (m a b)
@end example

Then register the rule for multiplying type N objects by type N objects.

@example
(cring:define-rule '* 'N 'N N*N))
@end example

Now we are ready to compute!

@example
(define (t)
  (define detM
    (+ (* (S g b)
          (+ (* (S f d)
                (- (* (S a f) (S d g)) (* (S a g) (S d f))))
             (* (S f f)
                (- (* (S a g) (S d d)) (* (S a d) (S d g))))
             (* (S f g)
                (- (* (S a d) (S d f)) (* (S a f) (S d d))))))
       (* (S g d)
          (+ (* (S f b)
                (- (* (S a g) (S d f)) (* (S a f) (S d g))))
             (* (S f f)
                (- (* (S a b) (S d g)) (* (S a g) (S d b))))
             (* (S f g)
                (- (* (S a f) (S d b)) (* (S a b) (S d f))))))
       (* (S g f)
          (+ (* (S f b)
                (- (* (S a d) (S d g)) (* (S a g) (S d d))))
             (* (S f d)
                (- (* (S a g) (S d b)) (* (S a b) (S d g))))
             (* (S f g)
                (- (* (S a b) (S d d)) (* (S a d) (S d b))))))
       (* (S g g)
          (+ (* (S f b)
                (- (* (S a f) (S d d)) (* (S a d) (S d f))))
             (* (S f d)
                (- (* (S a b) (S d f)) (* (S a f) (S d b))))
             (* (S f f)
                (- (* (S a d) (S d b)) (* (S a b) (S d d))))))))
  (* (S b e) (S c a) (S e c)
     detM
     ))
(pretty-print (t))
@print{}
(- (+ (m a c e b d f g)
      (m a c e b d g f)
      (m a c e b f d g)
      (m a c e b f g d)
      (m a c e b g d f)
      (m a c e b g f d))
   (* 2 (m a b e c) (m d f g))
   (* (m a c e b d) (m f g))
   (* (m a c e b f) (m d g))
   (* (m a c e b g) (m d f)))
@end example


@node Matrix Algebra,  , Commutative Rings, Mathematical Packages
@section Matrix Algebra

@include determ.txi


@node Database Packages, Other Packages, Mathematical Packages, Top
@chapter Database Packages

@menu
* Relational Database::         'relational-database
* Relational Infrastructure::   
* Weight-Balanced Trees::       'wt-tree
@end menu

@node Relational Database, Relational Infrastructure, Database Packages, Database Packages
@section Relational Database

@code{(require 'relational-database)}
@ftindex relational-database

This package implements a database system inspired by the Relational
Model (@cite{E. F. Codd, A Relational Model of Data for Large Shared
Data Banks}).  An SLIB relational database implementation can be created
from any @ref{Base Table} implementation.

Why relational database?  For motivations and design issues see@*
@uref{http://people.csail.mit.edu/jaffer/DBManifesto.html}.

@menu
* Using Databases::             'databases
* Table Operations::            
* Database Interpolation::      'database-interpolate
* Embedded Commands::           'database-commands
* Database Macros::             'within-database
* Database Browser::            'database-browse
@end menu

@node Using Databases, Table Operations, Relational Database, Relational Database
@subsection Using Databases

@include dbutil.txi


@node Table Operations, Database Interpolation, Using Databases, Relational Database
@subsection Table Operations

@noindent
These are the descriptions of the methods available from an open
relational table.  A method is retrieved from a table by calling
the table with the symbol name of the operation.  For example:

@example
((plat 'get 'processor) 'djgpp) @result{} i386
@end example

@noindent
Some operations described below require primary key arguments.  Primary
keys arguments are denoted @var{key1} @var{key2} @dots{}.  It is an
error to call an operation for a table which takes primary key arguments
with the wrong number of primary keys for that table.

@defop {Operation} {relational-table} get column-name
Returns a procedure of arguments @var{key1} @var{key2} @dots{} which
returns the value for the @var{column-name} column of the row associated
with primary keys @var{key1}, @var{key2} @dots{} if that row exists in
the table, or @code{#f} otherwise.

@example
((plat 'get 'processor) 'djgpp) @result{} i386
((plat 'get 'processor) 'be-os) @result{} #f
@end example
@end defop

@menu
* Single Row Operations::       
* Match-Keys::                  
* Multi-Row Operations::        
* Indexed Sequential Access Methods::  
* Sequential Index Operations::  
* Table Administration::        
@end menu


@node Single Row Operations, Match-Keys, Table Operations, Table Operations
@subsubsection Single Row Operations

@noindent
The term @dfn{row} used below refers to a Scheme list of values (one for
each column) in the order specified in the descriptor (table) for this
table.  Missing values appear as @code{#f}.  Primary keys must not
be missing.

@defop {Operation} {relational-table} row:insert
Adds the row @var{row} to this table.  If a row for the primary key(s)
specified by @var{row} already exists in this table an error is
signaled.  The value returned is unspecified.
@end defop

@example
@group
(define telephone-table-desc
        ((my-database 'create-table) 'telephone-table-desc))
(define ndrp (telephone-table-desc 'row:insert))
(ndrp '(1 #t name #f string))
(ndrp '(2 #f telephone
          (lambda (d)
            (and (string? d) (> (string-length d) 2)
                 (every
                  (lambda (c)
                    (memv c '(#\0 #\1 #\2 #\3 #\4 #\5 #\6 #\7 #\8 #\9
                                  #\+ #\( #\space #\) #\-)))
                  (string->list d))))
          string))
@end group
@end example

@defop {Operation} {relational-table} row:update
Returns a procedure of one argument, @var{row}, which adds the row,
@var{row}, to this table.  If a row for the primary key(s) specified by
@var{row} already exists in this table, it will be overwritten.  The
value returned is unspecified.
@end defop

@defop {Operation} {relational-table} row:retrieve
Returns a procedure of arguments @var{key1} @var{key2} @dots{} which
returns the row associated with primary keys @var{key1}, @var{key2}
@dots{} if it exists, or @code{#f} otherwise.
@end defop

@example
((plat 'row:retrieve) 'linux) @result{} (linux i386 linux gcc)
((plat 'row:retrieve) 'multics) @result{} #f
@end example

@defop {Operation} {relational-table} row:remove
Returns a procedure of arguments @var{key1} @var{key2} @dots{} which
removes and returns the row associated with primary keys @var{key1},
@var{key2} @dots{} if it exists, or @code{#f} otherwise.
@end defop

@defop {Operation} {relational-table} row:delete
Returns a procedure of arguments @var{key1} @var{key2} @dots{} which
deletes the row associated with primary keys @var{key1}, @var{key2}
@dots{} if it exists.  The value returned is unspecified.
@end defop


@node Match-Keys, Multi-Row Operations, Single Row Operations, Table Operations
@subsubsection Match-Keys

@noindent
@cindex match-keys
The (optional) @var{match-key1} @dots{} arguments are used to restrict
actions of a whole-table operation to a subset of that table.  Those
procedures (returned by methods) which accept match-key arguments will
accept any number of match-key arguments between zero and the number of
primary keys in the table.  Any unspecified @var{match-key} arguments
default to @code{#f}.

@noindent
The @var{match-key1} @dots{} restrict the actions of the table command
to those records whose primary keys each satisfy the corresponding
@var{match-key} argument.  The arguments and their actions are:

@quotation
@table @asis
@item @code{#f}
The false value matches any key in the corresponding position.
@item an object of type procedure
This procedure must take a single argument, the key in the corresponding
position.  Any key for which the procedure returns a non-false value is
a match; Any key for which the procedure returns a @code{#f} is not.
@item other values
Any other value matches only those keys @code{equal?} to it.
@end table
@end quotation

@defop {Operation} {relational-table} get* column-name
Returns a procedure of optional arguments @var{match-key1} @dots{} which
returns a list of the values for the specified column for all rows in
this table.  The optional @var{match-key1} @dots{} arguments restrict
actions to a subset of the table.

@example
((plat 'get* 'processor)) @result{}
(i386 i8086 i386 i8086 i386 i386 i8086 m68000
 m68000 m68000 m68000 m68000 powerpc)

((plat 'get* 'processor) #f) @result{}
(i386 i8086 i386 i8086 i386 i386 i8086 m68000
 m68000 m68000 m68000 m68000 powerpc)

(define (a-key? key)
   (char=? #\a (string-ref (symbol->string key) 0)))

((plat 'get* 'processor) a-key?) @result{}
(m68000 m68000 m68000 m68000 m68000 powerpc)

((plat 'get* 'name) a-key?) @result{}
(atari-st-turbo-c atari-st-gcc amiga-sas/c-5.10
 amiga-aztec amiga-dice-c aix)
@end example
@end defop


@node Multi-Row Operations, Indexed Sequential Access Methods, Match-Keys, Table Operations
@subsubsection Multi-Row Operations

@defop {Operation} {relational-table} row:retrieve*
Returns a procedure of optional arguments @var{match-key1} @dots{}
which returns a list of all rows in this table.  The optional
@var{match-key1} @dots{} arguments restrict actions to a subset of the
table.  For details see @xref{Match-Keys}.
@end defop

@example
((plat 'row:retrieve*) a-key?) @result{}
((atari-st-turbo-c m68000 atari turbo-c)
 (atari-st-gcc m68000 atari gcc)
 (amiga-sas/c-5.10 m68000 amiga sas/c)
 (amiga-aztec m68000 amiga aztec)
 (amiga-dice-c m68000 amiga dice-c)
 (aix powerpc aix -))
@end example

@defop {Operation} {relational-table} row:remove*
Returns a procedure of optional arguments @var{match-key1} @dots{} which
removes and returns a list of all rows in this table.  The optional
@var{match-key1} @dots{} arguments restrict actions to a subset of the
table.
@end defop

@defop {Operation} {relational-table} row:delete*
Returns a procedure of optional arguments @var{match-key1} @dots{}
which Deletes all rows from this table.  The optional @var{match-key1}
@dots{} arguments restrict deletions to a subset of the table.  The
value returned is unspecified.  The descriptor table and catalog entry
for this table are not affected.
@end defop

@defop {Operation} {relational-table} for-each-row
Returns a procedure of arguments @var{proc} @var{match-key1} @dots{}
which calls @var{proc} with each @var{row} in this table.  The
optional @var{match-key1} @dots{} arguments restrict actions to a
subset of the table.  For details see @xref{Match-Keys}.
@end defop

@noindent
Note that @code{row:insert*} and @code{row:update*} do @emph{not} use
match-keys.

@defop {Operation} {relational-table} row:insert*
Returns a procedure of one argument, @var{rows}, which adds each row in
the list of rows, @var{rows}, to this table.  If a row for the primary
key specified by an element of @var{rows} already exists in this table,
an error is signaled.  The value returned is unspecified.
@end defop

@defop {Operation} {relational-table} row:update*
Returns a procedure of one argument, @var{rows}, which adds each row in
the list of rows, @var{rows}, to this table.  If a row for the primary
key specified by an element of @var{rows} already exists in this table,
it will be overwritten.  The value returned is unspecified.
@end defop


@node Indexed Sequential Access Methods, Sequential Index Operations, Multi-Row Operations, Table Operations
@subsubsection Indexed Sequential Access Methods

@noindent
@cindex ISAM
@dfn{Indexed Sequential Access Methods} are a way of arranging
database information so that records can be accessed both by key and
by key sequence (ordering).  @dfn{ISAM} is not part of Codd's
relational model.

@noindent
Associative memory in B-Trees is an example of a database
implementation which can support a native key ordering.  SLIB's
@code{alist-table} implementation uses @code{sort} to implement
@code{for-each-row-in-order}, but does not support @code{isam-next}
and @code{isam-prev}.

@noindent
The multi-primary-key ordering employed by these operations is the
lexicographic collation of those primary-key fields in their given
order.  For example:

@example
(12 a 34) < (12 a 36) < (12 b 1) < (13 a 0)
@end example


@node Sequential Index Operations, Table Administration, Indexed Sequential Access Methods, Table Operations
@subsubsection Sequential Index Operations

@noindent
The following procedures are individually optional depending on the
base-table implememtation.  If an operation is @emph{not} supported,
then calling the table with that operation symbol will return false.

@defop {Operation} {relational-table} for-each-row-in-order
Returns a procedure of arguments @var{proc} @var{match-key1} @dots{}
which calls @var{proc} with each @var{row} in this table in the
(implementation-dependent) natural, repeatable ordering for rows.  The
optional @var{match-key1} @dots{} arguments restrict actions to a
subset of the table.  For details see @xref{Match-Keys}.
@end defop

@defop {Operation} {relational-table} isam-next
Returns a procedure of arguments @var{key1} @var{key2} @dots{} which
returns the key-list identifying the lowest record higher than
@var{key1} @var{key2} @dots{} which is stored in the relational-table;
or false if no higher record is present.
@end defop

@defop {Operation} {relational-table} isam-next column-name
The symbol @var{column-name} names a key field.  In the list returned
by @code{isam-next}, that field, or a field to its left, will be
changed.  This allows one to skip over less significant key fields.
@end defop

@defop {Operation} {relational-table} isam-prev
Returns a procedure of arguments @var{key1} @var{key2} @dots{} which
returns the key-list identifying the highest record less than
@var{key1} @var{key2} @dots{} which is stored in the relational-table;
or false if no lower record is present.
@end defop

@defop {Operation} {relational-table} isam-prev column-name
The symbol @var{column-name} names a key field.  In the list returned
by @code{isam-next}, that field, or a field to its left, will be
changed.  This allows one to skip over less significant key fields.
@end defop

For example, if a table has key fields:
@example
(col1 col2)
(9 5)
(9 6)
(9 7)
(9 8)
(12 5)
(12 6)
(12 7)
@end example

Then:
@example
((table 'isam-next)       '(9 5))       @result{} (9 6)
((table 'isam-next 'col2) '(9 5))       @result{} (9 6)
((table 'isam-next 'col1) '(9 5))       @result{} (12 5)
((table 'isam-prev)       '(12 7))      @result{} (12 6)
((table 'isam-prev 'col2) '(12 7))      @result{} (12 6)
((table 'isam-prev 'col1) '(12 7))      @result{} (9 8)
@end example


@node Table Administration,  , Sequential Index Operations, Table Operations
@subsubsection Table Administration

@defop {Operation} {relational-table} column-names
@defopx {Operation} {relational-table} column-foreigns
@defopx {Operation} {relational-table} column-domains
@defopx {Operation} {relational-table} column-types
Return a list of the column names, foreign-key table names, domain
names, or type names respectively for this table.  These 4 methods are
different from the others in that the list is returned, rather than a
procedure to obtain the list.
@end defop

@defop {Operation} {relational-table} primary-limit
Returns the number of primary keys fields in the relations in this
table.
@end defop

@defop {Operation} {relational-table} close-table
Subsequent operations to this table will signal an error.
@end defop


@node Database Interpolation, Embedded Commands, Table Operations, Relational Database
@subsection Database Interpolation

@code{(require 'database-interpolate)}

@noindent
Indexed sequential access methods allow finding the keys (having
associations) closest to a given value.  This facilitates the
interpolation of associations between those in the table.

@defun interpolate-from-table table column
@var{Table} should be a relational table with one numeric primary key
field which supports the @code{isam-prev} and @code{isam-next}
operations.  @var{column} should be a symbol or exact positive integer
designating a numerically valued column of @var{table}.

@code{interpolate-from-table} calculates and returns a value
proportionally intermediate between its values in the next and
previous key records contained in @var{table}.  For keys larger than
all the stored keys the value associated with the largest stored key
is used.  For keys smaller than all the stored keys the value
associated with the smallest stored key is used.
@end defun


@node Embedded Commands, Database Macros, Database Interpolation, Relational Database
@subsection Embedded Commands

@code{(require 'database-commands)}

@noindent
This enhancement wraps a utility layer on @code{relational-database}
which provides:

@itemize @bullet
@item
Automatic execution of initialization commands stored in database.
@item
Transparent execution of database commands stored in @code{*commands*}
table in database.
@end itemize

When an enhanced relational-database is called with a symbol which
matches a @var{name} in the @code{*commands*} table, the associated
procedure expression is evaluated and applied to the enhanced
relational-database.  A procedure should then be returned which the user
can invoke on (optional) arguments.

The command @code{*initialize*} is special.  If present in the
@code{*commands*} table, @code{open-database} or @code{open-database!}
will return the value of the @code{*initialize*} command.  Notice that
arbitrary code can be run when the @code{*initialize*} procedure is
automatically applied to the enhanced relational-database.

Note also that if you wish to shadow or hide from the user
relational-database methods described in @ref{Database Operations}, this
can be done by a dispatch in the closure returned by the
@code{*initialize*} expression rather than by entries in the
@code{*commands*} table if it is desired that the underlying methods
remain accessible to code in the @code{*commands*} table.


@menu
* Database Extension::          
* Command Intrinsics::          
* Define-tables Example::       
* The *commands* Table::        
* Command Service::             
* Command Example::             
@end menu


@node Database Extension, Command Intrinsics, Embedded Commands, Embedded Commands
@subsubsection Database Extension

@defun wrap-command-interface rdb
Returns relational database @var{rdb} wrapped with additional commands
defined in its *commands* table.
@end defun

@defun add-command-tables rdb
The relational database @var{rdb} must be mutable.
@var{add-command-tables} adds a *command* table to @var{rdb}; then
returns @code{(wrap-command-interface @var{rdb})}.
@end defun

@defun define-*commands* rdb spec-0 @dots{}

Adds commands to the @code{*commands*} table as specified in
@var{spec-0} @dots{} to the open relational-database @var{rdb}.  Each
@var{spec} has the form:

@lisp
((@r{<name>} @r{<rdb>}) @r{"comment"} @r{<expression1>} @r{<expression2>} @dots{})
@end lisp
or
@lisp
((@r{<name>} @r{<rdb>}) @r{<expression1>} @r{<expression2>} @dots{})
@end lisp

where @r{<name>} is the command name, @r{<rdb>} is a formal passed the
calling relational database, @r{"comment"} describes the
command, and @r{<expression1>}, @r{<expression1>}, @dots{} are the
body of the procedure.

@code{define-*commands*} adds to the @code{*commands*} table a command
@r{<name>}:

@lisp
(lambda (@r{<name>} @r{<rdb>}) @r{<expression1>} @r{<expression2>} @dots{})
@end lisp

@end defun


@defun open-command-database filename
@defunx open-command-database filename base-table-type
Returns an open enhanced relational database associated with
@var{filename}.  The database will be opened with base-table type
@var{base-table-type}) if supplied.  If @var{base-table-type} is not
supplied, @code{open-command-database} will attempt to deduce the correct
base-table-type.  If the database can not be opened or if it lacks the
@code{*commands*} table, @code{#f} is returned.
@end defun

@defun open-command-database! filename
@defunx open-command-database! filename base-table-type
Returns @emph{mutable} open enhanced relational database @dots{}
@end defun

@defun open-command-database database
Returns @var{database} if it is an immutable relational database; #f
otherwise.
@end defun

@defun open-command-database! database
Returns @var{database} if it is a mutable relational database; #f
otherwise.
@end defun


@node Command Intrinsics, Define-tables Example, Database Extension, Embedded Commands
@subsubsection Command Intrinsics

Some commands are defined in all extended relational-databases.  The are
called just like @ref{Database Operations}.

@defop {Operation} {relational-database} add-domain domain-row
Adds @var{domain-row} to the @dfn{domains} table if there is no row in
the domains table associated with key @code{(car @var{domain-row})} and
returns @code{#t}.  Otherwise returns @code{#f}.

For the fields and layout of the domain table,
@xref{Catalog Representation}.  Currently, these fields are
@itemize @bullet
@item
domain-name
@item
foreign-table
@item
domain-integrity-rule
@item
type-id
@item
type-param
@end itemize

The following example adds 3 domains to the @samp{build} database.
@samp{Optstring} is either a string or @code{#f}.  @code{filename} is a
string and @code{build-whats} is a symbol.

@example
(for-each (build 'add-domain)
          '((optstring #f
                       (lambda (x) (or (not x) (string? x)))
                       string
                       #f)
            (filename #f #f string #f)
            (build-whats #f #f symbol #f)))
@end example
@end defop

@defop {Operation} {relational-database} delete-domain domain-name
Removes and returns the @var{domain-name} row from the @dfn{domains}
table.
@end defop

@defop {Operation} {relational-database} domain-checker domain
Returns a procedure to check an argument for conformance to domain
@var{domain}.
@end defop


@node Define-tables Example, The *commands* Table, Command Intrinsics, Embedded Commands
@subsubsection Define-tables Example

@noindent
The following example shows a new database with the name of
@file{foo.db} being created with tables describing processor families
and processor/os/compiler combinations.  The database is then
solidified; saved and changed to immutable.

@example
(require 'databases)
@ftindex databases
(define my-rdb (create-database "foo.db" 'alist-table))
(define-tables my-rdb
  '(processor-family
    ((family    atom))
    ((also-ran  processor-family))
    ((m68000           #f)
     (m68030           m68000)
     (i386             i8086)
     (i8086            #f)
     (powerpc          #f)))

  '(platform
    ((name      symbol))
    ((processor processor-family)
     (os        symbol)
     (compiler  symbol))
    ((aix              powerpc aix     -)
     (amiga-dice-c     m68000  amiga   dice-c)
     (amiga-aztec      m68000  amiga   aztec)
     (amiga-sas/c-5.10 m68000  amiga   sas/c)
     (atari-st-gcc     m68000  atari   gcc)
     (atari-st-turbo-c m68000  atari   turbo-c)
     (borland-c-3.1    i8086   ms-dos  borland-c)
     (djgpp            i386    ms-dos  gcc)
     (linux            i386    linux   gcc)
     (microsoft-c      i8086   ms-dos  microsoft-c)
     (os/2-emx         i386    os/2    gcc)
     (turbo-c-2        i8086   ms-dos  turbo-c)
     (watcom-9.0       i386    ms-dos  watcom))))

(solidify-database my-rdb)
@end example


@node The *commands* Table, Command Service, Define-tables Example, Embedded Commands
@subsubsection The *commands* Table

@noindent
The table @code{*commands*} in an @dfn{enhanced} relational-database has
the fields (with domains):
@example
@group
PRI name        symbol
    parameters  parameter-list
    procedure   expression
    documentation string
@end group
@end example

The @code{parameters} field is a foreign key (domain
@code{parameter-list}) of the @code{*catalog-data*} table and should
have the value of a table described by @code{*parameter-columns*}.  This
@code{parameter-list} table describes the arguments suitable for passing
to the associated command.  The intent of this table is to be of a form
such that different user-interfaces (for instance, pull-down menus or
plain-text queries) can operate from the same table.  A
@code{parameter-list} table has the following fields:
@example
@group
PRI index       ordinal
    name        symbol
    arity       parameter-arity
    domain      domain
    defaulter   expression
    expander    expression
    documentation string
@end group
@end example

The @code{arity} field can take the values:

@table @code
@item single
Requires a single parameter of the specified domain.
@item optional
A single parameter of the specified domain or zero parameters is
acceptable.
@item boolean
A single boolean parameter or zero parameters (in which case @code{#f}
is substituted) is acceptable.
@item nary
Any number of parameters of the specified domain are acceptable.  The
argument passed to the command function is always a list of the
parameters.
@item nary1
One or more of parameters of the specified domain are acceptable.  The
argument passed to the command function is always a list of the
parameters.
@end table

The @code{domain} field specifies the domain which a parameter or
parameters in the @code{index}th field must satisfy.

The @code{defaulter} field is an expression whose value is either
@code{#f} or a procedure of one argument (the parameter-list) which
returns a @emph{list} of the default value or values as appropriate.
Note that since the @code{defaulter} procedure is called every time a
default parameter is needed for this column, @dfn{sticky} defaults can
be implemented using shared state with the domain-integrity-rule.


@node Command Service, Command Example, The *commands* Table, Embedded Commands
@subsubsection Command Service

@defun make-command-server rdb table-name
Returns a procedure of 2 arguments, a (symbol) command and a call-back
procedure.  When this returned procedure is called, it looks up
@var{command} in table @var{table-name} and calls the call-back
procedure with arguments:
@table @var
@item command
The @var{command}
@item command-value
The result of evaluating the expression in the @var{procedure} field of
@var{table-name} and calling it with @var{rdb}.
@item parameter-name
A list of the @dfn{official} name of each parameter.  Corresponds to the
@code{name} field of the @var{command}'s parameter-table.
@item positions
A list of the positive integer index of each parameter.  Corresponds to
the @code{index} field of the @var{command}'s parameter-table.
@item arities
A list of the arities of each parameter.  Corresponds to the
@code{arity} field of the @var{command}'s parameter-table.  For a
description of @code{arity} see table above.
@item types
A list of the type name of each parameter.  Correspnds to the
@code{type-id} field of the contents of the @code{domain} of the
@var{command}'s parameter-table.
@item defaulters
A list of the defaulters for each parameter.  Corresponds to
the @code{defaulters} field of the @var{command}'s parameter-table.
@item domain-integrity-rules
A list of procedures (one for each parameter) which tests whether a
value for a parameter is acceptable for that parameter.  The procedure
should be called with each datum in the list for @code{nary} arity
parameters.
@item aliases
A list of lists of @code{(@r{alias} @r{parameter-name})}.  There can be
more than one alias per @var{parameter-name}.
@end table
@end defun

For information about parameters, @xref{Parameter lists}.


@node Command Example,  , Command Service, Embedded Commands
@subsubsection Command Example

Here is an example of setting up a command with arguments and parsing
those arguments from a @code{getopt} style argument list
(@pxref{Getopt}).

@example
(require 'database-commands)
@ftindex database-commands
(require 'databases)
@ftindex databases
(require 'getopt-parameters)
@ftindex getopt-parameters
(require 'parameters)
@ftindex parameters
(require 'getopt)
@ftindex getopt
(require 'fluid-let)
(require 'printf)

(define my-rdb (add-command-tables (create-database #f 'alist-table)))

(define-tables my-rdb
  '(foo-params
    *parameter-columns*
    *parameter-columns*
    ((1 single-string single string
        (lambda (pl) '("str")) #f "single string")
     (2 nary-symbols nary symbol
        (lambda (pl) '()) #f "zero or more symbols")
     (3 nary1-symbols nary1 symbol
        (lambda (pl) '(symb)) #f "one or more symbols")
     (4 optional-number optional ordinal
        (lambda (pl) '()) #f "zero or one number")
     (5 flag boolean boolean
        (lambda (pl) '(#f)) #f "a boolean flag")))
  '(foo-pnames
    ((name string))
    ((parameter-index ordinal))
    (("s" 1)
     ("single-string" 1)
     ("n" 2)
     ("nary-symbols" 2)
     ("N" 3)
     ("nary1-symbols" 3)
     ("o" 4)
     ("optional-number" 4)
     ("f" 5)
     ("flag" 5)))
  '(my-commands
    ((name symbol))
    ((parameters parameter-list)
     (parameter-names parameter-name-translation)
     (procedure expression)
     (documentation string))
    ((foo
      foo-params
      foo-pnames
      (lambda (rdb) (lambda args (print args)))
      "test command arguments"))))

(define (dbutil:serve-command-line rdb command-table command argv)
  (set! *argv* (if (vector? argv) (vector->list argv) argv))
  ((make-command-server rdb command-table)
   command
   (lambda (comname comval options positions
                    arities types defaulters dirs aliases)
     (apply comval (getopt->arglist options positions
                    arities types defaulters dirs aliases)))))

(define (cmd . opts)
  (fluid-let ((*optind* 1))
    (printf "%-34s @result{} "
            (call-with-output-string
             (lambda (pt) (write (cons 'cmd opts) pt))))
    (set! opts (cons "cmd" opts))
    (force-output)
    (dbutil:serve-command-line
     my-rdb 'my-commands 'foo (length opts) opts)))

(cmd)                              @result{} ("str" () (symb) () #f)
(cmd "-f")                         @result{} ("str" () (symb) () #t)
(cmd "--flag")                     @result{} ("str" () (symb) () #t)
(cmd "-o177")                      @result{} ("str" () (symb) (177) #f)
(cmd "-o" "177")                   @result{} ("str" () (symb) (177) #f)
(cmd "--optional" "621")           @result{} ("str" () (symb) (621) #f)
(cmd "--optional=621")             @result{} ("str" () (symb) (621) #f)
(cmd "-s" "speciality")            @result{} ("speciality" () (symb) () #f)
(cmd "-sspeciality")               @result{} ("speciality" () (symb) () #f)
(cmd "--single" "serendipity")     @result{} ("serendipity" () (symb) () #f)
(cmd "--single=serendipity")       @result{} ("serendipity" () (symb) () #f)
(cmd "-n" "gravity" "piety")       @result{} ("str" () (piety gravity) () #f)
(cmd "-ngravity" "piety")          @result{} ("str" () (piety gravity) () #f)
(cmd "--nary" "chastity")          @result{} ("str" () (chastity) () #f)
(cmd "--nary=chastity" "")         @result{} ("str" () ( chastity) () #f)
(cmd "-N" "calamity")              @result{} ("str" () (calamity) () #f)
(cmd "-Ncalamity")                 @result{} ("str" () (calamity) () #f)
(cmd "--nary1" "surety")           @result{} ("str" () (surety) () #f)
(cmd "--nary1=surety")             @result{} ("str" () (surety) () #f)
(cmd "-N" "levity" "fealty")       @result{} ("str" () (fealty levity) () #f)
(cmd "-Nlevity" "fealty")          @result{} ("str" () (fealty levity) () #f)
(cmd "--nary1" "surety" "brevity") @result{} ("str" () (brevity surety) () #f)
(cmd "--nary1=surety" "brevity")   @result{} ("str" () (brevity surety) () #f)
(cmd "-?")
@print{}
Usage: cmd [OPTION ARGUMENT ...] ...

  -f, --flag
  -o, --optional[=]<number>
  -n, --nary[=]<symbols> ...
  -N, --nary1[=]<symbols> ...
  -s, --single[=]<string>

ERROR: getopt->parameter-list "unrecognized option" "-?"
@end example


@node Database Macros, Database Browser, Embedded Commands, Relational Database
@subsection Database Macros

@code{(require 'within-database)}

The object-oriented programming interface to SLIB relational databases
has failed to support clear, understandable, and modular code-writing
for database applications.

This seems to be a failure of the object-oriented paradigm where the
type of an object is not manifest (or even traceable) in source code.

@code{within-database}, along with the @samp{databases} package,
reorganizes high-level database functions toward a more declarative
style.  Using this package, one can tag database table and command
declarations for emacs:

@example
etags -lscheme -r'/ *(define-\(command\|table\) (\([^; \t]+\)/\2/' \
      source1.scm ...
@end example
@c ))
@menu
* Within-database::             
* Within-database Example::     
@end menu

@node Within-database, Within-database Example, Database Macros, Database Macros
@subsubsection Within-database

@defun within-database database statement-1 @dots{}

@code{within-database} creates a lexical scope in which the commands
@code{define-table} and @code{define-command} create tables and
@code{*commands*}-table entries respectively in open relational
database @var{database}.  The expressions in `within-database' form
are executed in order.

@code{within-database} Returns @var{database}.
@end defun

@deffn Syntax define-command (@r{<name>} @r{<rdb>}) @r{"comment"} @r{<expression1>} @r{<expression2>} @dots{}
@deffnx Syntax define-command (@r{<name>} @r{<rdb>}) @r{<expression1>} @r{<expression2>} @dots{}

Adds to the @code{*commands*} table a command
@r{<name>}:

@lisp
(lambda (@r{<name>} @r{<rdb>}) @r{<expression1>} @r{<expression2>} @dots{})
@end lisp

@end deffn

@deffn Syntax define-table @r{<name>} @r{<descriptor-name>} @r{<descriptor-name>} @r{<rows>}
@deffnx Syntax define-table @r{<name>} @r{<primary-key-fields>} @r{<other-fields>} @r{<rows>}

where @r{<name>} is the table name, @r{<descriptor-name>} is the symbol
name of a descriptor table, @r{<primary-key-fields>} and
@r{<other-fields>} describe the primary keys and other fields
respectively, and @r{<rows>} is a list of data rows to be added to the
table.

@r{<primary-key-fields>} and @r{<other-fields>} are lists of field
descriptors of the form:

@lisp
(@r{<column-name>} @r{<domain>})
@end lisp
or
@lisp
(@r{<column-name>} @r{<domain>} @r{<column-integrity-rule>})
@end lisp

where @r{<column-name>} is the column name, @r{<domain>} is the domain
of the column, and @r{<column-integrity-rule>} is an expression whose
value is a procedure of one argument (which returns @code{#f} to signal
an error).

If @r{<domain>} is not a defined domain name and it matches the name of
this table or an already defined (in one of @var{spec-0} @dots{}) single
key field table, a foreign-key domain will be created for it.

@end deffn

@defun add-macro-support database
The relational database @var{database} must be mutable.
@code{add-macro-support} adds a @code{*macros*} table and
@code{define-macro} macro to @var{database}; then @var{database} is
returned.
@end defun

@deffn Syntax define-macro (@r{<name>} @r{arg1} @dots{}) @r{"comment"} @r{<expression1>} @r{<expression2>} @dots{}
@deffnx Syntax define-macro (@r{<name>} @r{arg1} @dots{}) @r{<expression1>} @r{<expression2>} @dots{}
Adds a macro @r{<name>} to the @code{*macros*}.

@emph{Note:} @code{within-database} creates lexical scope where not
only @code{define-command} and @code{define-table}, but every command
and macro are defined, ie.:

@example
(within-database my-rdb
  (define-command (message rdb)
    (lambda (msg)
      (display "message: ")
      (display msg)
      (newline)))
  (message "Defining FOO...")
  ;; ... defining FOO ...
  (message "Defining BAR...")
  ;; ... defining BAR ...
  )
@end example
@end deffn


@node Within-database Example,  , Within-database, Database Macros
@subsubsection Within-database Example

@noindent
Here is an example of @code{within-database} macros:

@example
(require 'within-database)

(define my-rdb
  (add-command-tables
   (create-database "foo.db" 'alist-table)))

(within-database my-rdb
  (define-command (*initialize* rdb)
    "Print Welcome"
    (display "Welcome")
    (newline)
    rdb)
  (define-command (without-documentation rdb)
    (display "without-documentation called")
    (newline))
  (define-table (processor-family
                 ((family   atom))
                 ((also-ran processor-family)))
    (m68000  #f)
    (m68030  m68000)
    (i386    i8086)
    (i8086   #f)
    (powerpc #f))
  (define-table (platform
                 ((name symbol))
                 ((processor processor-family)
                  (os        symbol)
                  (compiler  symbol)))
    (aix              powerpc aix     -)
    ;; ...
    (amiga-aztec      m68000  amiga   aztec)
    (amiga-sas/c-5.10 m68000  amiga   sas/c)
    (atari-st-gcc     m68000  atari   gcc)
    ;; ...
    (watcom-9.0       i386    ms-dos  watcom))
  (define-command (get-processor rdb)
    "Get processor for given platform."
    (((rdb 'open-table) 'platform #f) 'get 'processor)))

(close-database my-rdb)

(set! my-rdb (open-command-database! "foo.db"))
@print{}
Welcome

(my-rdb 'without-documentation)
@print{}
without-documentation called

((my-rdb 'get-processor) 'amiga-sas/c-5.10)
@result{} m68000

(close-database my-rdb)
@end example


@node Database Browser,  , Database Macros, Relational Database
@subsection Database Browser

(require 'database-browse)

@deffn {Procedure} browse database

Prints the names of all the tables in @var{database} and sets browse's
default to @var{database}.
@end deffn
@deffn {Procedure} browse

Prints the names of all the tables in the default database.
@end deffn
@deffn {Procedure} browse table-name

For each record of the table named by the symbol @var{table-name},
prints a line composed of all the field values.
@end deffn
@deffn {Procedure} browse pathname

Opens the database named by the string @var{pathname}, prints the names
of all its tables, and sets browse's default to the database.
@end deffn
@deffn {Procedure} browse database table-name

Sets browse's default to @var{database} and prints the records of the
table named by the symbol @var{table-name}.
@end deffn
@deffn {Procedure} browse pathname table-name

Opens the database named by the string @var{pathname} and sets browse's
default to it; @code{browse} prints the records of the table named by
the symbol @var{table-name}.
@end deffn


@node Relational Infrastructure, Weight-Balanced Trees, Relational Database, Database Packages
@section Relational Infrastructure


@menu
* Base Table::                  
* Catalog Representation::      
* Relational Database Objects::  
* Database Operations::         
@end menu

@node Base Table, Catalog Representation, Relational Infrastructure, Relational Infrastructure
@subsection Base Table

@cindex base-table
A @dfn{base-table} is the primitive database layer upon which SLIB
relational databases are built.  At the minimum, it must support the
types integer, symbol, string, and boolean.  The base-table may restrict
the size of integers, symbols, and strings it supports.

A base table implementation is available as the value of the identifier
naming it (eg. @var{alist-table}) after requiring the symbol of that
name.

@deftp {Feature} alist-table
@code{(require 'alist-table)}
@ftindex alist-table

Association-list base tables support all Scheme types and are suitable
for small databases.  In order to be retrieved after being written to a
file, the data stored should include only objects which are readable and
writeable in the Scheme implementation.

The @dfn{alist-table} base-table implementation is included in the
SLIB distribution.
@end deftp

@dfn{WB} is a B-tree database package with SCM interfaces.  Being
disk-based, WB databases readily store and access hundreds of
megabytes of data.  WB comes with two base-table embeddings.

@deftp {Feature} wb-table
@code{(require 'wb-table)}
@ftindex wb-table

@cindex WB
@code{wb-table} supports scheme expressions for keys and values whose
text representations are less than 255 characters in length.
@xref{wb-table, , , wb, WB}.
@end deftp


@deftp {Feature} rwb-isam
@code{(require 'rwb-isam)}
@ftindex rwb-isam

@dfn{rwb-isam} is a sophisticated base-table implementation built on
WB and SCM which uses binary numerical formats for key and non-key
fields.  It supports IEEE floating-point and fixed-precision integer
keys with the correct numerical collation order.
@end deftp

This rest of this section documents the interface for a base table
implementation from which the @ref{Relational Database} package
constructs a Relational system.  It will be of interest primarily to
those wishing to port or write new base-table implementations.

@defvar *base-table-implementations*
To support automatic dispatch for @code{open-database}, each base-table
module adds an association to @var{*base-table-implementations*} when
loaded.  This association is the list of the base-table symbol and the
value returned by @code{(make-relational-system @var{base-table})}.
@end defvar

@menu
* The Base::                    
* Base Tables::                 
* Base Field Types::            
* Composite Keys::              
* Base Record Operations::      
* Match Keys::                  
* Aggregate Base Operations::   
* Base ISAM Operations::        
@end menu

@node The Base, Base Tables, Base Table, Base Table
@subsubsection The Base

All of these functions are accessed through a single procedure by
calling that procedure with the symbol name of the operation.  A
procedure will be returned if that operation is supported and @code{#f}
otherwise.  For example:

@example
@group
(require 'alist-table)
@ftindex alist-table
@findex alist-table
(define my-base (alist-table 'make-base))
my-base         @result{} *a procedure*
(define foo (alist-table 'foo))
foo             @result{} #f
@end group
@end example

@defop {Operation} {base-table} make-base filename key-dimension column-types
Returns a new, open, low-level database (collection of tables)
associated with @var{filename}.  This returned database has an empty
table associated with @var{catalog-id}.  The positive integer
@var{key-dimension} is the number of keys composed to make a
@var{primary-key} for the catalog table.  The list of symbols
@var{column-types} describes the types of each column for that table.
If the database cannot be created as specified, @code{#f} is returned.

Calling the @code{close-base} method on this database and possibly other
operations will cause @var{filename} to be written to.  If
@var{filename} is @code{#f} a temporary, non-disk based database will be
created if such can be supported by the base table implelentation.
@end defop

@defop {Operation} {base-table} open-base filename mutable
Returns an open low-level database associated with @var{filename}.  If
@var{mutable} is @code{#t}, this database will have methods capable of
effecting change to the database.  If @var{mutable} is @code{#f}, only
methods for inquiring the database will be available.  If the database
cannot be opened as specified @code{#f} is returned.

Calling the @code{close-base} (and possibly other) method on a
@var{mutable} database will cause @var{filename} to be written to.
@end defop

@defop {Operation} {base-table} write-base lldb filename
Causes the low-level database @var{lldb} to be written to
@var{filename}.  If the write is successful, also causes @var{lldb} to
henceforth be associated with @var{filename}.  Calling the
@code{close-database} (and possibly other) method on @var{lldb} may
cause @var{filename} to be written to.  If @var{filename} is @code{#f}
this database will be changed to a temporary, non-disk based database if
such can be supported by the underlying base table implelentation.  If
the operations completed successfully, @code{#t} is returned.
Otherwise, @code{#f} is returned.
@end defop

@defop {Operation} {base-table} sync-base lldb
Causes the file associated with the low-level database @var{lldb} to be
updated to reflect its current state.  If the associated filename is
@code{#f}, no action is taken and @code{#f} is returned.  If this
operation completes successfully, @code{#t} is returned.  Otherwise,
@code{#f} is returned.
@end defop

@defop {Operation} {base-table} close-base lldb
Causes the low-level database @var{lldb} to be written to its associated
file (if any).  If the write is successful, subsequent operations to
@var{lldb} will signal an error.  If the operations complete
successfully, @code{#t} is returned.  Otherwise, @code{#f} is returned.
@end defop


@node Base Tables, Base Field Types, The Base, Base Table
@subsubsection Base Tables

@defop {Operation} {base-table} make-table lldb key-dimension column-types
Returns the ordinal @var{base-id} for a new base table, otherwise
returns @code{#f}.  The base table can then be opened using
@code{(open-table @var{lldb} @var{base-id})}.  The positive integer
@var{key-dimension} is the number of keys composed to make a
@var{primary-key} for this table.  The list of symbols
@var{column-types} describes the types of each column.
@end defop

@defop {Operation} {base-table} open-table lldb base-id key-dimension column-types
Returns a @var{handle} for an existing base table in the low-level
database @var{lldb} if that table exists and can be opened in the mode
indicated by @var{mutable}, otherwise returns @code{#f}.

As with @code{make-table}, the positive integer @var{key-dimension} is
the number of keys composed to make a @var{primary-key} for this table.
The list of symbols @var{column-types} describes the types of each
column.
@end defop

@defop {Operation} {base-table} kill-table lldb base-id key-dimension column-types
Returns @code{#t} if the base table associated with @var{base-id} was
removed from the low level database @var{lldb}, and @code{#f} otherwise.
@end defop

@defop {Operation} {base-table} catalog-id
A constant @var{base-id} ordinal suitable for passing as a parameter to
@code{open-table}.  @var{catalog-id} will be used as the base table for
the system catalog.
@end defop


@node Base Field Types, Composite Keys, Base Tables, Base Table
@subsubsection Base Field Types

@defop {Operation} {base-table} supported-type? symbol
Returns @code{#t} if @var{symbol} names a type allowed as a column
value by the implementation, and @code{#f} otherwise.  At a minimum,
an implementation must support the types @code{integer},
@code{ordinal}, @code{symbol}, @code{string}, and @code{boolean}.
@end defop

@defop {Operation} {base-table} supported-key-type? symbol
Returns @code{#t} if @var{symbol} names a type allowed as a key value
by the implementation, and @code{#f} otherwise.  At a minimum, an
implementation must support the types @code{ordinal}, and
@code{symbol}.
@end defop

@noindent
An @dfn{ordinal} is an exact positive integer.  The other types are
standard Scheme.


@node Composite Keys, Base Record Operations, Base Field Types, Base Table
@subsubsection Composite Keys

@defop {Operation} {base-table} make-keyifier-1 type
Returns a procedure which accepts a single argument which must be of
type @var{type}.  This returned procedure returns an object suitable for
being a @var{key} argument in the functions whose descriptions follow.

Any 2 arguments of the supported type passed to the returned function
which are not @code{equal?} must result in returned values which are not
@code{equal?}.
@end defop

@defop {Operation} {base-table} make-list-keyifier key-dimension types
The list of symbols @var{types} must have at least @var{key-dimension}
elements.  Returns a procedure which accepts a list of length
@var{key-dimension} and whose types must corresopond to the types named
by @var{types}.  This returned procedure combines the elements of its
list argument into an object suitable for being a @var{key} argument in
the functions whose descriptions follow.

Any 2 lists of supported types (which must at least include symbols and
non-negative integers) passed to the returned function which are not
@code{equal?} must result in returned values which are not
@code{equal?}.
@end defop

@defop {Operation} {base-table} make-key-extractor key-dimension types column-number
Returns a procedure which accepts objects produced by application of the
result of @code{(make-list-keyifier @var{key-dimension} @var{types})}.
This procedure returns a @var{key} which is @code{equal?} to the
@var{column-number}th element of the list which was passed to create
@var{composite-key}.  The list @var{types} must have at least
@var{key-dimension} elements.
@end defop

@defop {Operation} {base-table} make-key->list key-dimension types
Returns a procedure which accepts objects produced by application of
the result of @code{(make-list-keyifier @var{key-dimension}
@var{types})}.  This procedure returns a list of @var{key}s which are
elementwise @code{equal?} to the list which was passed to create
@var{composite-key}.
@end defop


@node Base Record Operations, Match Keys, Composite Keys, Base Table
@subsubsection Base Record Operations

@noindent
In the following functions, the @var{key} argument can always be assumed
to be the value returned by a call to a @emph{keyify} routine.

@defop {Operation} {base-table} present? handle key
Returns a non-@code{#f} value if there is a row associated with
@var{key} in the table opened in @var{handle} and @code{#f} otherwise.
@end defop

@defop {Operation} {base-table} make-getter key-dimension types
Returns a procedure which takes arguments @var{handle} and @var{key}.
This procedure returns a list of the non-primary values of the relation
(in the base table opened in @var{handle}) whose primary key is
@var{key} if it exists, and @code{#f} otherwise.
@end defop

@noindent
@code{make-getter-1} is a new operation.  The relational-database
module works with older base-table implementations by using
@code{make-getter}.

@defop {Operation} {base-table} make-getter-1 key-dimension types index
Returns a procedure which takes arguments @var{handle} and @var{key}.
This procedure returns the value of the @var{index}th field (in the
base table opened in @var{handle}) whose primary key is @var{key} if
it exists, and @code{#f} otherwise.

@var{index} must be larger than @var{key-dimension}.
@end defop

@defop {Operation} {base-table} make-putter key-dimension types
Returns a procedure which takes arguments @var{handle} and @var{key} and
@var{value-list}.  This procedure associates the primary key @var{key}
with the values in @var{value-list} (in the base table opened in
@var{handle}) and returns an unspecified value.
@end defop

@defop {Operation} {base-table} delete handle key
Removes the row associated with @var{key} from the table opened in
@var{handle}.  An unspecified value is returned.
@end defop


@node Match Keys, Aggregate Base Operations, Base Record Operations, Base Table
@subsubsection Match Keys

@noindent
@cindex match-keys
@cindex match
@cindex wild-card
A @var{match-keys} argument is a list of length equal to
the number of primary keys.  The @var{match-keys} restrict the actions
of the table command to those records whose primary keys all satisfy the
corresponding element of the @var{match-keys} list.  The elements and
their actions are:

@quotation
@table @asis
@item @code{#f}
The false value matches any key in the corresponding position.
@item an object of type procedure
This procedure must take a single argument, the key in the corresponding
position.  Any key for which the procedure returns a non-false value is
a match; Any key for which the procedure returns a @code{#f} is not.
@item other values
Any other value matches only those keys @code{equal?} to it.
@end table
@end quotation


@node Aggregate Base Operations, Base ISAM Operations, Match Keys, Base Table
@subsubsection Aggregate Base Operations

@noindent
The @var{key-dimension} and @var{column-types} arguments are needed to
decode the composite-keys for matching with @var{match-keys}.

@defop {Operation} {base-table} delete* handle key-dimension column-types match-keys
Removes all rows which satisfy @var{match-keys} from the table opened in
@var{handle}.  An unspecified value is returned.
@end defop

@defop {Operation} {base-table} for-each-key handle procedure key-dimension column-types match-keys
Calls @var{procedure} once with each @var{key} in the table opened in
@var{handle} which satisfy @var{match-keys} in an unspecified order.
An unspecified value is returned.
@end defop

@defop {Operation} {base-table} map-key handle procedure key-dimension column-types match-keys
Returns a list of the values returned by calling @var{procedure} once
with each @var{key} in the table opened in @var{handle} which satisfy
@var{match-keys} in an unspecified order.
@end defop


@node Base ISAM Operations,  , Aggregate Base Operations, Base Table
@subsubsection Base ISAM Operations

@noindent
These operations are optional for a Base-Table implementation.

@defop {Operation} {base-table} ordered-for-each-key handle procedure key-dimension column-types match-keys
Calls @var{procedure} once with each @var{key} in the table opened in
@var{handle} which satisfy @var{match-keys} in the natural order for
the types of the primary key fields of that table.  An unspecified value
is returned.
@end defop

@defop {Operation} {base-table} make-nexter handle key-dimension column-types index
Returns a procedure of arguments @var{key1} @var{key2} @dots{} which
returns the key-list identifying the lowest record higher than
@var{key1} @var{key2} @dots{} which is stored in the base-table and
which differs in column @var{index} or a lower indexed key; or false
if no higher record is present.
@end defop

@defop {Operation} {base-table} make-prever handle key-dimension column-types index
Returns a procedure of arguments @var{key1} @var{key2} @dots{} which
returns the key-list identifying the highest record less than
@var{key1} @var{key2} @dots{} which is stored in the base-table and
which differs in column @var{index} or a lower indexed key; or false
if no higher record is present.
@end defop


@node Catalog Representation, Relational Database Objects, Base Table, Relational Infrastructure
@subsection Catalog Representation

@noindent
Each database (in an implementation) has a @dfn{system catalog} which
describes all the user accessible tables in that database (including
itself).

@noindent
The system catalog base table has the following fields.  @code{PRI}
indicates a primary key for that table.

@example
@group
PRI table-name
    column-limit            the highest column number
    coltab-name             descriptor table name
    bastab-id               data base table identifier
    user-integrity-rule
    view-procedure          A scheme thunk which, when called,
                            produces a handle for the view.  coltab
                            and bastab are specified if and only if
                            view-procedure is not.
@end group
@end example

@noindent
Descriptors for base tables (not views) are tables (pointed to by
system catalog).  Descriptor (base) tables have the fields:

@example
@group
PRI column-number           sequential integers from 1
    primary-key?            boolean TRUE for primary key components
    column-name
    column-integrity-rule
    domain-name
@end group
@end example

@noindent
A @dfn{primary key} is any column marked as @code{primary-key?} in the
corresponding descriptor table.  All the @code{primary-key?} columns
must have lower column numbers than any non-@code{primary-key?} columns.
Every table must have at least one primary key.  Primary keys must be
sufficient to distinguish all rows from each other in the table.  All of
the system defined tables have a single primary key.

@noindent
A @dfn{domain} is a category describing the allowable values to occur in
a column.  It is described by a (base) table with the fields:

@example
@group
PRI domain-name
    foreign-table
    domain-integrity-rule
    type-id
    type-param
@end group
@end example

@noindent
The @dfn{type-id} field value is a symbol.  This symbol may be used by
the underlying base table implementation in storing that field.

@noindent
If the @code{foreign-table} field is non-@code{#f} then that field names
a table from the catalog.  The values for that domain must match a
primary key of the table referenced by the @var{type-param} (or
@code{#f}, if allowed).  This package currently does not support
composite foreign-keys.

@noindent
The types for which support is planned are:
@example
@group
    atom
    symbol
    string                  [<length>]
    number                  [<base>]
    money                   <currency>
    date-time
    boolean

    foreign-key             <table-name>
    expression
    virtual                 <expression>
@end group
@end example


@node Relational Database Objects, Database Operations, Catalog Representation, Relational Infrastructure
@subsection Relational Database Objects

@noindent
This object-oriented interface is deprecated for typical database
applications; @ref{Using Databases} provides an application programmer
interface which is easier to understand and use.

@defun make-relational-system base-table-implementation

Returns a procedure implementing a relational database using the
@var{base-table-implementation}.

All of the operations of a base table implementation are accessed
through a procedure defined by @code{require}ing that implementation.
Similarly, all of the operations of the relational database
implementation are accessed through the procedure returned by
@code{make-relational-system}.  For instance, a new relational database
could be created from the procedure returned by
@code{make-relational-system} by:

@example
(require 'alist-table)
@ftindex alist-table
(define relational-alist-system
        (make-relational-system alist-table))
(define create-alist-database
        (relational-alist-system 'create-database))
(define my-database
        (create-alist-database "mydata.db"))
@end example
@end defun

@noindent
What follows are the descriptions of the methods available from
relational system returned by a call to @code{make-relational-system}.

@defop {Operation} {relational-system} create-database filename

Returns an open, nearly empty relational database associated with
@var{filename}.  The only tables defined are the system catalog and
domain table.  Calling the @code{close-database} method on this database
and possibly other operations will cause @var{filename} to be written
to.  If @var{filename} is @code{#f} a temporary, non-disk based database
will be created if such can be supported by the underlying base table
implelentation.  If the database cannot be created as specified
@code{#f} is returned.  For the fields and layout of descriptor tables,
@ref{Catalog Representation}
@end defop

@defop {Operation} {relational-system} open-database filename mutable?

Returns an open relational database associated with @var{filename}.  If
@var{mutable?} is @code{#t}, this database will have methods capable of
effecting change to the database.  If @var{mutable?} is @code{#f}, only
methods for inquiring the database will be available.  Calling the
@code{close-database} (and possibly other) method on a @var{mutable?}
database will cause @var{filename} to be written to.  If the database
cannot be opened as specified @code{#f} is returned.
@end defop


@node Database Operations,  , Relational Database Objects, Relational Infrastructure
@subsection Database Operations

@noindent
This object-oriented interface is deprecated for typical database
applications; @ref{Using Databases} provides an application programmer
interface which is easier to understand and use.

@noindent
These are the descriptions of the methods available from an open
relational database.  A method is retrieved from a database by calling
the database with the symbol name of the operation.  For example:

@example
(define my-database
        (create-alist-database "mydata.db"))
(define telephone-table-desc
        ((my-database 'create-table) 'telephone-table-desc))
@end example

@defop {Operation} {relational-database} close-database
Causes the relational database to be written to its associated file (if
any).  If the write is successful, subsequent operations to this
database will signal an error.  If the operations completed
successfully, @code{#t} is returned.  Otherwise, @code{#f} is returned.
@end defop

@defop {Operation} {relational-database} write-database filename
Causes the relational database to be written to @var{filename}.  If the
write is successful, also causes the database to henceforth be
associated with @var{filename}.  Calling the @code{close-database} (and
possibly other) method on this database will cause @var{filename} to be
written to.  If @var{filename} is @code{#f} this database will be
changed to a temporary, non-disk based database if such can be supported
by the underlying base table implelentation.  If the operations
completed successfully, @code{#t} is returned.  Otherwise, @code{#f} is
returned.
@end defop

@defop {Operation} {relational-database} sync-database
Causes any pending updates to the database file to be written out.  If
the operations completed successfully, @code{#t} is returned.
Otherwise, @code{#f} is returned.
@end defop

@defop {Operation} {relational-database} solidify-database
Causes any pending updates to the database file to be written out.  If
the writes completed successfully, then the database is changed to be
immutable and @code{#t} is returned.  Otherwise, @code{#f} is returned.
@end defop

@defop {Operation} {relational-database} table-exists? table-name
Returns @code{#t} if @var{table-name} exists in the system catalog,
otherwise returns @code{#f}.
@end defop

@defop {Operation} {relational-database} open-table table-name mutable?
Returns a @dfn{methods} procedure for an existing relational table in
this database if it exists and can be opened in the mode indicated by
@var{mutable?}, otherwise returns @code{#f}.
@end defop

@noindent
These methods will be present only in mutable databases.

@defop {Operation} {relational-database} delete-table table-name
Removes and returns the @var{table-name} row from the system catalog if
the table or view associated with @var{table-name} gets removed from the
database, and @code{#f} otherwise.
@end defop

@defop {Operation} {relational-database} create-table table-desc-name
Returns a methods procedure for a new (open) relational table for
describing the columns of a new base table in this database, otherwise
returns @code{#f}.  For the fields and layout of descriptor tables,
@xref{Catalog Representation}.
@end defop

@defop {Operation} {relational-database} create-table table-name table-desc-name
Returns a methods procedure for a new (open) relational table with
columns as described by @var{table-desc-name}, otherwise returns
@code{#f}.
@end defop

@defop {Operation} {relational-database} create-view ??
@defopx {Operation} {relational-database} project-table ??
@defopx {Operation} {relational-database} restrict-table ??
@defopx {Operation} {relational-database} cart-prod-tables ??
Not yet implemented.
@end defop


@node Weight-Balanced Trees,  , Relational Infrastructure, Database Packages
@section Weight-Balanced Trees

@code{(require 'wt-tree)}
@ftindex wt-tree

@cindex trees, balanced binary
@cindex balanced binary trees
@cindex binary trees
@cindex weight-balanced binary trees
Balanced binary trees are a useful data structure for maintaining large
sets of ordered objects or sets of associations whose keys are ordered.
MIT Scheme has an comprehensive implementation of weight-balanced binary
trees which has several advantages over the other data structures for
large aggregates:

@itemize @bullet
@item
In addition to the usual element-level operations like insertion,
deletion and lookup, there is a full complement of collection-level
operations, like set intersection, set union and subset test, all of
which are implemented with good orders of growth in time and space.
This makes weight balanced trees ideal for rapid prototyping of
functionally derived specifications.

@item
An element in a tree may be indexed by its position under the ordering
of the keys, and the ordinal position of an element may be determined,
both with reasonable efficiency.

@item
Operations to find and remove minimum element make weight balanced trees
simple to use for priority queues.

@item
The implementation is @emph{functional} rather than @emph{imperative}.
This means that operations like `inserting' an association in a tree do
not destroy the old tree, in much the same way that @code{(+ 1 x)}
modifies neither the constant 1 nor the value bound to @code{x}.  The
trees are referentially transparent thus the programmer need not worry
about copying the trees.  Referential transparency allows space
efficiency to be achieved by sharing subtrees.

@end itemize

These features make weight-balanced trees suitable for a wide range of
applications, especially those that
require large numbers of sets or discrete maps.  Applications that have
a few global databases and/or concentrate on element-level operations like
insertion and lookup are probably better off using hash-tables or
red-black trees.

The @emph{size} of a tree is the number of associations that it
contains.  Weight balanced binary trees are balanced to keep the sizes
of the subtrees of each node within a constant factor of each other.
This ensures logarithmic times for single-path operations (like lookup
and insertion).  A weight balanced tree takes space that is proportional
to the number of associations in the tree.  For the current
implementation, the constant of proportionality is six words per
association.

@cindex binary trees, as sets
@cindex binary trees, as discrete maps
@cindex sets, using binary trees
@cindex discrete maps, using binary trees
Weight balanced trees can be used as an implementation for either
discrete sets or discrete maps (associations).  Sets are implemented by
ignoring the datum that is associated with the key.  Under this scheme
if an associations exists in the tree this indicates that the key of the
association is a member of the set.  Typically a value such as
@code{()}, @code{#t} or @code{#f} is associated with the key.

Many operations can be viewed as computing a result that, depending on
whether the tree arguments are thought of as sets or maps, is known by
two different names.  An example is @code{wt-tree/member?}, which, when
regarding the tree argument as a set, computes the set membership
operation, but, when regarding the tree as a discrete map,
@code{wt-tree/member?} is the predicate testing if the map is defined at
an element in its domain.  Most names in this package have been chosen
based on interpreting the trees as sets, hence the name
@code{wt-tree/member?} rather than @code{wt-tree/defined-at?}.


@cindex run-time-loadable option
@cindex option, run-time-loadable
The weight balanced tree implementation is a run-time-loadable option.
To use weight balanced trees, execute

@example
(load-option 'wt-tree)
@end example
@ftindex load-option

@noindent
once before calling any of the procedures defined here.


@menu
* Construction of Weight-Balanced Trees::  
* Basic Operations on Weight-Balanced Trees::  
* Advanced Operations on Weight-Balanced Trees::  
* Indexing Operations on Weight-Balanced Trees::  
@end menu

@node Construction of Weight-Balanced Trees, Basic Operations on Weight-Balanced Trees, Weight-Balanced Trees, Weight-Balanced Trees
@subsection Construction of Weight-Balanced Trees

Binary trees require there to be a total order on the keys used to
arrange the elements in the tree.  Weight balanced trees are organized
by @emph{types}, where the type is an object encapsulating the ordering
relation.  Creating a tree is a two-stage process.  First a tree type
must be created from the predicate which gives the ordering.  The tree
type is then used for making trees, either empty or singleton trees or
trees from other aggregate structures like association lists.  Once
created, a tree `knows' its type and the type is used to test
compatibility between trees in operations taking two trees.  Usually a
small number of tree types are created at the beginning of a program and
used many times throughout the program's execution.

@deffn {procedure+} make-wt-tree-type key<?
This procedure creates and returns a new tree type based on the ordering
predicate @var{key<?}.
@var{Key<?} must be a total ordering, having the property that for all
key values @code{a}, @code{b} and @code{c}:

@example
(key<? a a)                         @result{} #f
(and (key<? a b) (key<? b a))       @result{} #f
(if (and (key<? a b) (key<? b c))
    (key<? a c)
    #t)                             @result{} #t
@end example

@noindent
Two key values are assumed to be equal if neither is less than the other
by @var{key<?}.

Each call to @code{make-wt-tree-type} returns a distinct value, and
trees are only compatible if their tree types are @code{eq?}.  A
consequence is that trees that are intended to be used in binary tree
operations must all be created with a tree type originating from the
same call to @code{make-wt-tree-type}.
@end deffn

@defvr {variable+} number-wt-type
A standard tree type for trees with numeric keys.  @code{Number-wt-type}
could have been defined by

@example
(define number-wt-type (make-wt-tree-type  <))
@end example
@end defvr

@defvr {variable+} string-wt-type
A standard tree type for trees with string keys.  @code{String-wt-type}
could have been defined by

@example
(define string-wt-type (make-wt-tree-type  string<?))
@end example
@end defvr



@deffn {procedure+} make-wt-tree wt-tree-type
This procedure creates and returns a newly allocated weight balanced
tree.  The tree is empty, i.e. it contains no associations.
@var{Wt-tree-type} is a weight balanced tree type obtained by calling
@code{make-wt-tree-type}; the returned tree has this type.
@end deffn

@deffn {procedure+} singleton-wt-tree wt-tree-type key datum
This procedure creates and returns a newly allocated weight balanced
tree.  The tree contains a single association, that of @var{datum} with
@var{key}.  @var{Wt-tree-type} is a weight balanced tree type obtained
by calling @code{make-wt-tree-type}; the returned tree has this type.
@end deffn

@deffn {procedure+} alist->wt-tree tree-type alist
Returns a newly allocated weight-balanced tree that contains the same
associations as @var{alist}.  This procedure is equivalent to:

@example
(lambda (type alist)
  (let ((tree (make-wt-tree type)))
    (for-each (lambda (association)
                (wt-tree/add! tree
                              (car association)
                              (cdr association)))
              alist)
    tree))
@end example
@end deffn


@node Basic Operations on Weight-Balanced Trees, Advanced Operations on Weight-Balanced Trees, Construction of Weight-Balanced Trees, Weight-Balanced Trees
@subsection Basic Operations on Weight-Balanced Trees

This section describes the basic tree operations on weight balanced
trees.  These operations are the usual tree operations for insertion,
deletion and lookup, some predicates and a procedure for determining the
number of associations in a tree.

@c @deffn {procedure+} wt-tree? object
@c Returns @code{#t} if @var{object} is a weight-balanced tree, otherwise
@c returns @code{#f}.
@c @end deffn

@deffn {procedure+} wt-tree/empty? wt-tree
Returns @code{#t} if @var{wt-tree} contains no associations, otherwise
returns @code{#f}.
@end deffn

@deffn {procedure+} wt-tree/size wt-tree
Returns the number of associations in @var{wt-tree}, an exact
non-negative integer.  This operation takes constant time.
@end deffn


@deffn {procedure+} wt-tree/add wt-tree key datum
Returns a new tree containing all the associations in @var{wt-tree} and
the association of @var{datum} with @var{key}.  If @var{wt-tree} already
had an association for @var{key}, the new association overrides the old.
The average and worst-case times required by this operation are
proportional to the logarithm of the number of associations in
@var{wt-tree}.
@end deffn

@deffn {procedure+} wt-tree/add! wt-tree key datum
Associates @var{datum} with @var{key} in @var{wt-tree} and returns an
unspecified value.  If @var{wt-tree} already has an association for
@var{key}, that association is replaced.  The average and worst-case
times required by this operation are proportional to the logarithm of
the number of associations in @var{wt-tree}.
@end deffn

@deffn {procedure+} wt-tree/member? key wt-tree
Returns @code{#t} if @var{wt-tree} contains an association for
@var{key}, otherwise returns @code{#f}.  The average and worst-case
times required by this operation are proportional to the logarithm of
the number of associations in @var{wt-tree}.
@end deffn

@deffn {procedure+} wt-tree/lookup wt-tree key default
Returns the datum associated with @var{key} in @var{wt-tree}.  If
@var{wt-tree} doesn't contain an association for @var{key},
@var{default} is returned.  The average and worst-case times required by
this operation are proportional to the logarithm of the number of
associations in @var{wt-tree}.
@end deffn

@deffn {procedure+} wt-tree/delete wt-tree key
Returns a new tree containing all the associations in @var{wt-tree},
except that if @var{wt-tree} contains an association for @var{key}, it
is removed from the result.  The average and worst-case times required
by this operation are proportional to the logarithm of the number of
associations in @var{wt-tree}.
@end deffn

@deffn {procedure+} wt-tree/delete! wt-tree key
If @var{wt-tree} contains an association for @var{key} the association
is removed.  Returns an unspecified value.  The average and worst-case
times required by this operation are proportional to the logarithm of
the number of associations in @var{wt-tree}.
@end deffn


@node Advanced Operations on Weight-Balanced Trees, Indexing Operations on Weight-Balanced Trees, Basic Operations on Weight-Balanced Trees, Weight-Balanced Trees
@subsection Advanced Operations on Weight-Balanced Trees

In the following the @emph{size} of a tree is the number of associations
that the tree contains, and a @emph{smaller} tree contains fewer
associations.

@deffn {procedure+} wt-tree/split< wt-tree bound
Returns a new tree containing all and only the associations in
@var{wt-tree} which have a key that is less than @var{bound} in the
ordering relation of the tree type of @var{wt-tree}.  The average and
worst-case times required by this operation are proportional to the
logarithm of the size of @var{wt-tree}.
@end deffn

@deffn {procedure+} wt-tree/split> wt-tree bound
Returns a new tree containing all and only the associations in
@var{wt-tree} which have a key that is greater than @var{bound} in the
ordering relation of the tree type of @var{wt-tree}.  The average and
worst-case times required by this operation are proportional to the
logarithm of size of @var{wt-tree}.
@end deffn

@deffn {procedure+} wt-tree/union wt-tree-1 wt-tree-2
Returns a new tree containing all the associations from both trees.
This operation is asymmetric: when both trees have an association for
the same key, the returned tree associates the datum from @var{wt-tree-2}
with the key.  Thus if the trees are viewed as discrete maps then
@code{wt-tree/union} computes the map override of @var{wt-tree-1} by
@var{wt-tree-2}.  If the trees are viewed as sets the result is the set
union of the arguments.
The worst-case time required by this operation
is proportional to the sum of the sizes of both trees.
If the minimum key of one tree is greater than the maximum key of
the other tree then the time required is at worst proportional to
the logarithm of the size of the larger tree.
@end deffn

@deffn {procedure+} wt-tree/intersection wt-tree-1 wt-tree-2
Returns a new tree containing all and only those associations from
@var{wt-tree-1} which have keys appearing as the key of an association
in @var{wt-tree-2}.  Thus the associated data in the result are those
from @var{wt-tree-1}.  If the trees are being used as sets the result is
the set intersection of the arguments.  As a discrete map operation,
@code{wt-tree/intersection} computes the domain restriction of
@var{wt-tree-1} to (the domain of) @var{wt-tree-2}.
The time required by this operation is never worse that proportional to
the sum of the sizes of the trees.
@end deffn

@deffn {procedure+} wt-tree/difference wt-tree-1 wt-tree-2
Returns a new tree containing all and only those associations from
@var{wt-tree-1} which have keys that @emph{do not} appear as the key of
an association in @var{wt-tree-2}.  If the trees are viewed as sets the
result is the asymmetric set difference of the arguments.  As a discrete
map operation, it computes the domain restriction of @var{wt-tree-1} to
the complement of (the domain of) @var{wt-tree-2}.
The time required by this operation is never worse that proportional to
the sum of the sizes of the trees.
@end deffn


@deffn {procedure+} wt-tree/subset? wt-tree-1 wt-tree-2
Returns @code{#t} iff the key of each association in @var{wt-tree-1} is
the key of some association in @var{wt-tree-2}, otherwise returns @code{#f}.
Viewed as a set operation, @code{wt-tree/subset?} is the improper subset
predicate.
A proper subset predicate can be constructed:

@example
(define (proper-subset? s1 s2)
  (and (wt-tree/subset? s1 s2)
       (< (wt-tree/size s1) (wt-tree/size s2))))
@end example

As a discrete map operation, @code{wt-tree/subset?} is the subset
test on the domain(s) of the map(s).  In the worst-case the time
required by this operation is proportional to the size of
@var{wt-tree-1}.
@end deffn


@deffn {procedure+} wt-tree/set-equal? wt-tree-1 wt-tree-2
Returns @code{#t} iff for every association in @var{wt-tree-1} there is
an association in @var{wt-tree-2} that has the same key, and @emph{vice
versa}.

Viewing the arguments as sets @code{wt-tree/set-equal?} is the set
equality predicate.  As a map operation it determines if two maps are
defined on the same domain.

This procedure is equivalent to

@example
(lambda (wt-tree-1 wt-tree-2)
  (and (wt-tree/subset? wt-tree-1 wt-tree-2
       (wt-tree/subset? wt-tree-2 wt-tree-1)))
@end example

In the worst-case the time required by this operation is proportional to
the size of the smaller tree.
@end deffn


@deffn {procedure+} wt-tree/fold combiner initial wt-tree
This procedure reduces @var{wt-tree} by combining all the associations,
using an reverse in-order traversal, so the associations are visited in
reverse order.  @var{Combiner} is a procedure of three arguments: a key,
a datum and the accumulated result so far.  Provided @var{combiner}
takes time bounded by a constant, @code{wt-tree/fold} takes time
proportional to the size of @var{wt-tree}.

A sorted association list can be derived simply:

@example
(wt-tree/fold  (lambda (key datum list)
                 (cons (cons key datum) list))
               '()
               @var{wt-tree}))
@end example

The data in the associations can be summed like this:

@example
(wt-tree/fold  (lambda (key datum sum) (+ sum datum))
               0
               @var{wt-tree})
@end example
@end deffn

@deffn {procedure+} wt-tree/for-each action wt-tree
This procedure traverses the tree in-order, applying @var{action} to
each association.
The associations are processed in increasing order of their keys.
@var{Action} is a procedure of two arguments which take the key and
datum respectively of the association.
Provided @var{action} takes time bounded by a constant,
@code{wt-tree/for-each} takes time proportional to in the size of
@var{wt-tree}.
The example prints the tree:

@example
(wt-tree/for-each (lambda (key value)
                    (display (list key value)))
                  @var{wt-tree}))
@end example
@end deffn

@deffn {procedure+} wt-tree/union-merge wt-tree-1 wt-tree-2 merge
Returns a new tree containing all the associations from both trees.  If
both trees have an association for the same key, the datum associated
with that key in the result tree is computed by applying the procedure
@var{merge} to the key, the value from @var{wt-tree-1} and the value
from @var{wt-tree-2}.  @var{Merge} is of the form

@example
(lambda (@var{key} @var{datum-1} @var{datum-2}) ...)
@end example

If some key occurs only in one tree, that association will appear in the
result tree without being processed by @var{merge}, so for this
operation to make sense, either @var{merge} must have both a right and
left identity that correspond to the association being absent in one of
the trees, or some guarantee must be made, for example, all the keys in
one tree are known to occur in the other.

These are all reasonable procedures for @var{merge}

@example
@group
(lambda (key val1 val2) (+ val1 val2))
(lambda (key val1 val2) (append val1 val2))
(lambda (key val1 val2) (wt-tree/union val1 val2))
@end group
@end example

However, a procedure like

@example
(lambda (key val1 val2) (- val1 val2))
@end example

would result in a subtraction of the data for all associations with keys
occuring in both trees but associations with keys occuring in only the
second tree would be copied, not negated, as is presumably be intent.
The programmer might ensure that this never happens.

This procedure has the same time behavior as @code{wt-tree/union} but
with a slightly worse constant factor.  Indeed, @code{wt-tree/union}
might have been defined like this:

@example
@group
(define (wt-tree/union tree1 tree2)
  (wt-tree/union-merge tree1 tree2
                       (lambda (key val1 val2) val2)))
@end group
@end example
@end deffn

The @var{merge} procedure takes the @var{key} as a parameter in case the
data are not independent of the key.


@node Indexing Operations on Weight-Balanced Trees,  , Advanced Operations on Weight-Balanced Trees, Weight-Balanced Trees
@subsection Indexing Operations on Weight-Balanced Trees

Weight balanced trees support operations that view the tree as sorted
sequence of associations.  Elements of the sequence can be accessed by
position, and the position of an element in the sequence can be
determined, both in logarthmic time.

@deffn {procedure+} wt-tree/index wt-tree index
@deffnx {procedure+} wt-tree/index-datum wt-tree index
@deffnx {procedure+} wt-tree/index-pair wt-tree index
Returns the 0-based @var{index}th association of @var{wt-tree} in the
sorted sequence under the tree's ordering relation on the keys.
@code{wt-tree/index} returns the @var{index}th key,
@code{wt-tree/index-datum} returns the datum associated with the
@var{index}th key and @code{wt-tree/index-pair} returns a new pair
@code{(@var{key} . @var{datum})} which is the @code{cons} of the
@var{index}th key and its datum.  The average and worst-case times
required by this operation are proportional to the logarithm of the
number of associations in the tree.

These operations signal an error if the tree is empty, if
@var{index}@code{<0}, or if @var{index} is greater than or equal to the
number of associations in the tree.

Indexing can be used to find the median and maximum keys in the tree as
follows:
@end deffn

@example
median:  (wt-tree/index @var{wt-tree} (quotient (wt-tree/size @var{wt-tree}) 2))

maximum: (wt-tree/index @var{wt-tree} (-1+ (wt-tree/size @var{wt-tree})))
@end example

@deffn {procedure+} wt-tree/rank wt-tree key
Determines the 0-based position of @var{key} in the sorted sequence of
the keys under the tree's ordering relation, or @code{#f} if the tree
has no association with for @var{key}.  This procedure returns either an
exact non-negative integer or @code{#f}.  The average and worst-case
times required by this operation are proportional to the logarithm of
the number of associations in the tree.
@end deffn

@deffn {procedure+} wt-tree/min wt-tree
@deffnx {procedure+} wt-tree/min-datum wt-tree
@deffnx {procedure+} wt-tree/min-pair wt-tree
Returns the association of @var{wt-tree} that has the least key under
the tree's ordering relation.  @code{wt-tree/min} returns the least key,
@code{wt-tree/min-datum} returns the datum associated with the least key
and @code{wt-tree/min-pair} returns a new pair @code{(key . datum)}
which is the @code{cons} of the minimum key and its datum.  The average
and worst-case times required by this operation are proportional to the
logarithm of the number of associations in the tree.

These operations signal an error if the tree is empty.
They could be written
@example
(define (wt-tree/min tree)        (wt-tree/index tree 0))
(define (wt-tree/min-datum tree)  (wt-tree/index-datum tree 0))
(define (wt-tree/min-pair tree)   (wt-tree/index-pair tree 0))
@end example
@end deffn

@deffn {procedure+} wt-tree/delete-min wt-tree
Returns a new tree containing all of the associations in @var{wt-tree}
except the association with the least key under the @var{wt-tree}'s
ordering relation.  An error is signalled if the tree is empty.  The
average and worst-case times required by this operation are proportional
to the logarithm of the number of associations in the tree.  This
operation is equivalent to

@example
(wt-tree/delete @var{wt-tree} (wt-tree/min @var{wt-tree}))
@end example
@end deffn


@deffn {procedure+} wt-tree/delete-min! wt-tree
Removes the association with the least key under the @var{wt-tree}'s
ordering relation.  An error is signalled if the tree is empty.  The
average and worst-case times required by this operation are proportional
to the logarithm of the number of associations in the tree.  This
operation is equivalent to

@example
(wt-tree/delete! @var{wt-tree} (wt-tree/min @var{wt-tree}))
@end example
@end deffn


@node Other Packages, About SLIB, Database Packages, Top
@chapter Other Packages

@menu
* Data Structures::             Various data structures.
* Sorting and Searching::       
* Procedures::                  Miscellaneous utility procedures.
* Standards Support::           Support for Scheme Standards.
* Session Support::             REPL and Debugging.
* System Interface::            'system, 'getenv, and other programs.
* Extra-SLIB Packages::         Outside the envelope.
@end menu


@node Data Structures, Sorting and Searching, Other Packages, Other Packages
@section Data Structures

@menu
* Arrays::                      'array
* Subarrays::                   'subarray
* Array Mapping::               'array-for-each
* Array Interpolation::         'array-interpolate
* Association Lists::           'alist
* Byte::                        'byte
* Byte/Number Conversions::     'byte-number
* MAT-File Format::             'matfile
* Portable Image Files::        'pnm
* Collections::                 'collect
* Dynamic Data Type::           'dynamic
* Hash Tables::                 'hash-table
* Object::                      'object
* Priority Queues::             'priority-queue
* Queues::                      'queue
* Records::                     'record
@end menu

@node Arrays, Subarrays, Data Structures, Data Structures
@subsection Arrays

@include array.txi


@node Subarrays, Array Mapping, Arrays, Data Structures
@subsection Subarrays

@include subarray.txi


@node Array Mapping, Array Interpolation, Subarrays, Data Structures
@subsection Array Mapping

@include arraymap.txi


@node Array Interpolation, Association Lists, Array Mapping, Data Structures
@subsection Array Interpolation

@include linterp.txi


@node Association Lists, Byte, Array Interpolation, Data Structures
@subsection Association Lists

@include alist.txi


@node Byte, Byte/Number Conversions, Association Lists, Data Structures
@subsection Byte

@include byte.txi


@node Byte/Number Conversions, MAT-File Format, Byte, Data Structures
@subsection Byte/Number Conversions

@include bytenumb.txi


@node MAT-File Format, Portable Image Files, Byte/Number Conversions, Data Structures
@subsection MAT-File Format

@include matfile.txi


@node Portable Image Files, Collections, MAT-File Format, Data Structures
@subsection Portable Image Files

@include pnm.txi


@node Collections, Dynamic Data Type, Portable Image Files, Data Structures
@subsection Collections

@c Much of the documentation in this section was written by Dave Love
@c (d.love@dl.ac.uk) -- don't blame Ken Dickey for its faults.
@c but we can blame him for not writing it!

@code{(require 'collect)}
@ftindex collect

@noindent
Routines for managing collections.  Collections are aggregate data
structures supporting iteration over their elements, similar to the
Dylan(TM) language, but with a different interface.  They have
@dfn{elements} indexed by corresponding @dfn{keys}, although the keys
may be implicit (as with lists).

@noindent
New types of collections may be defined as YASOS objects (@pxref{Yasos}).
They must support the following operations:

@itemize @bullet
@item
@code{(collection? @var{self})} (always returns @code{#t});

@item
@code{(size @var{self})} returns the number of elements in the collection;

@item
@code{(print @var{self} @var{port})} is a specialized print operation
for the collection which prints a suitable representation on the given
@var{port} or returns it as a string if @var{port} is @code{#t};

@item
@findex gen-elts
@code{(gen-elts @var{self})} returns a thunk which on successive
invocations yields elements of @var{self} in order or gives an error if
it is invoked more than @code{(size @var{self})} times;

@item
@findex gen-keys
@code{(gen-keys @var{self})} is like @code{gen-elts}, but yields the
collection's keys in order.
@end itemize

@noindent
They might support specialized @code{for-each-key} and
@code{for-each-elt} operations.



@defun collection? obj
A predicate, true initially of lists, vectors and strings.  New sorts of
collections must answer @code{#t} to @code{collection?}.
@end defun

@deffn {Procedure} map-elts proc collection1 @dots{}
@deffnx {Procedure} do-elts proc collection1 @dots{}
@var{proc} is a procedure taking as many arguments as there are
@var{collections} (at least one).  The @var{collections} are iterated
over in their natural order and @var{proc} is applied to the elements
yielded by each iteration in turn.  The order in which the arguments are
supplied corresponds to te order in which the @var{collections} appear.
@code{do-elts} is used when only side-effects of @var{proc} are of
interest and its return value is unspecified.  @code{map-elts} returns a
collection (actually a vector) of the results of the applications of
@var{proc}.

Example:
@lisp
(map-elts + (list 1 2 3) (vector 1 2 3))
   @result{} #(2 4 6)
@end lisp
@end deffn

@deffn {Procedure} map-keys proc collection1 @dots{}
@deffnx {Procedure} do-keys proc collection1 @dots{}
These are analogous to @code{map-elts} and @code{do-elts}, but each
iteration is over the @var{collections}' @emph{keys} rather than their
elements.

Example:
@lisp
(map-keys + (list 1 2 3) (vector 1 2 3))
   @result{} #(0 2 4)
@end lisp
@end deffn

@deffn {Procedure} for-each-key collection proc
@deffnx {Procedure} for-each-elt collection proc
These are like @code{do-keys} and @code{do-elts} but only for a single
collection; they are potentially more efficient.
@end deffn

@defun reduce proc seed collection1 @dots{}
A generalization of the list-based @code{reduce-init}
(@pxref{Lists as sequences}) to collections.

Examples:
@lisp
(reduce + 0 (vector 1 2 3))
   @result{} 6
(reduce union '() '((a b c) (b c d) (d a)))
   @result{} (c b d a).
@end lisp

@code{Reduce} called with two arguments will work as does the
procedure of the same name from @xref{Common List Functions}.
@ftindex common-list-functions 
@end defun

@defun any? pred collection1 @dots{}
A generalization of the list-based @code{some}
(@pxref{Lists as sequences}) to collections.

Example:
@lisp
(any? odd? (list 2 3 4 5))
   @result{} #t
@end lisp
@end defun

@defun every? pred collection1 @dots{}
A generalization of the list-based @code{every}
(@pxref{Lists as sequences}) to collections.

Example:
@lisp
(every? collection? '((1 2) #(1 2)))
   @result{} #t
@end lisp
@end defun

@defun empty? collection
Returns @code{#t} iff there are no elements in @var{collection}.

@code{(empty? @var{collection}) @equiv{} (zero? (size @var{collection}))}
@end defun

@defun size collection
Returns the number of elements in @var{collection}.
@end defun

@defun Setter list-ref
See @ref{Setters} for a definition of @dfn{setter}.  N.B.
@code{(setter list-ref)} doesn't work properly for element 0 of a
list.
@end defun

Here is a sample collection: @code{simple-table} which is also a
@code{table}.
@lisp
(define-predicate TABLE?)
(define-operation (LOOKUP table key failure-object))
(define-operation (ASSOCIATE! table key value)) ;; returns key
(define-operation (REMOVE! table key))          ;; returns value

(define (MAKE-SIMPLE-TABLE)
  (let ( (table (list)) )
    (object
     ;; table behaviors
     ((TABLE? self) #t)
     ((SIZE self) (size table))
     ((PRINT self port) (format port "#<SIMPLE-TABLE>"))
     ((LOOKUP self key failure-object)
      (cond
       ((assq key table) => cdr)
       (else failure-object)
       ))
     ((ASSOCIATE! self key value)
      (cond
       ((assq key table)
        => (lambda (bucket) (set-cdr! bucket value) key))
       (else
        (set! table (cons (cons key value) table))
        key)
       ))
     ((REMOVE! self key);; returns old value
      (cond
       ((null? table) (slib:error "TABLE:REMOVE! Key not found: " key))
       ((eq? key (caar table))
        (let ( (value (cdar table)) )
          (set! table (cdr table))
          value)
        )
       (else
        (let loop ( (last table) (this (cdr table)) )
          (cond
           ((null? this)
            (slib:error "TABLE:REMOVE! Key not found: " key))
           ((eq? key (caar this))
            (let ( (value (cdar this)) )
              (set-cdr! last (cdr this))
              value)
            )
           (else
            (loop (cdr last) (cdr this)))
           ) ) )
       ))
@group
     ;; collection behaviors
     ((COLLECTION? self) #t)
     ((GEN-KEYS self) (collect:list-gen-elts (map car table)))
     ((GEN-ELTS self) (collect:list-gen-elts (map cdr table)))
     ((FOR-EACH-KEY self proc)
      (for-each (lambda (bucket) (proc (car bucket))) table)
      )
     ((FOR-EACH-ELT self proc)
      (for-each (lambda (bucket) (proc (cdr bucket))) table)
      ) ) ) )
@end group
@end lisp


@node Dynamic Data Type, Hash Tables, Collections, Data Structures
@subsection Dynamic Data Type

@code{(require 'dynamic)}
@ftindex dynamic

@defun make-dynamic obj
Create and returns a new @dfn{dynamic} whose global value is @var{obj}.
@end defun

@defun dynamic? obj
Returns true if and only if @var{obj} is a dynamic.  No object
satisfying @code{dynamic?} satisfies any of the other standard type
predicates.
@end defun

@defun dynamic-ref dyn
Return the value of the given dynamic in the current dynamic
environment.
@end defun

@deffn {Procedure} dynamic-set! dyn obj
Change the value of the given dynamic to @var{obj} in the current
dynamic environment.  The returned value is unspecified.
@end deffn

@defun call-with-dynamic-binding dyn obj thunk
Invoke and return the value of the given thunk in a new, nested dynamic
environment in which the given dynamic has been bound to a new location
whose initial contents are the value @var{obj}.  This dynamic
environment has precisely the same extent as the invocation of the thunk
and is thus captured by continuations created within that invocation and
re-established by those continuations when they are invoked.
@end defun

The @code{dynamic-bind} macro is not implemented.


@node Hash Tables, Object, Dynamic Data Type, Data Structures
@subsection Hash Tables

@include hashtab.txi


@node Object, Priority Queues, Hash Tables, Data Structures
@subsection Macroless Object System

@include object.texi


@node Priority Queues, Queues, Object, Data Structures
@subsection Priority Queues

@include priorque.txi


@node Queues, Records, Priority Queues, Data Structures
@subsection Queues

@include queue.txi


@node Records,  , Queues, Data Structures
@subsection Records

@code{(require 'record)}
@ftindex record

The Record package provides a facility for user to define their own
record data types.

@defun make-record-type type-name field-names
Returns a @dfn{record-type descriptor}, a value representing a new data
type disjoint from all others.  The @var{type-name} argument must be a
string, but is only used for debugging purposes (such as the printed
representation of a record of the new type).  The @var{field-names}
argument is a list of symbols naming the @dfn{fields} of a record of the
new type.  It is an error if the list contains any duplicates.  It is
unspecified how record-type descriptors are represented.
@end defun

@c @defun make-record-sub-type type-name field-names rtd
@c Returns a @dfn{record-type descriptor}, a value representing a new data
@c type, disjoint from all others.  The @var{type-name} argument must be a
@c string.  The @var{field-names} argument is a list of symbols naming the
@c additional @dfn{fields} to be appended to @var{field-names} of
@c @var{rtd}.  It is an error if the combined list contains any
@c duplicates.
@c
@c Record-modifiers and record-accessors for @var{rtd} work for the new
@c record-sub-type as well.  But record-modifiers and record-accessors for
@c the new record-sub-type will not neccessarily work for @var{rtd}.
@c @end defun

@defun record-constructor rtd [field-names]
Returns a procedure for constructing new members of the type represented
by @var{rtd}.  The returned procedure accepts exactly as many arguments
as there are symbols in the given list, @var{field-names}; these are
used, in order, as the initial values of those fields in a new record,
which is returned by the constructor procedure.  The values of any
fields not named in that list are unspecified.  The @var{field-names}
argument defaults to the list of field names in the call to
@code{make-record-type} that created the type represented by @var{rtd};
if the @var{field-names} argument is provided, it is an error if it
contains any duplicates or any symbols not in the default list.
@end defun

@defun record-predicate rtd
Returns a procedure for testing membership in the type represented by
@var{rtd}.  The returned procedure accepts exactly one argument and
returns a true value if the argument is a member of the indicated record
type; it returns a false value otherwise.
@end defun

@c @defun record-sub-predicate rtd
@c Returns a procedure for testing membership in the type represented by
@c @var{rtd} or its parents.  The returned procedure accepts exactly one
@c argument and returns a true value if the argument is a member of the
@c indicated record type or its parents; it returns a false value
@c otherwise.
@c @end defun

@defun record-accessor rtd field-name
Returns a procedure for reading the value of a particular field of a
member of the type represented by @var{rtd}.  The returned procedure
accepts exactly one argument which must be a record of the appropriate
type; it returns the current value of the field named by the symbol
@var{field-name} in that record.  The symbol @var{field-name} must be a
member of the list of field-names in the call to @code{make-record-type}
that created the type represented by @var{rtd}.
@end defun


@defun record-modifier rtd field-name
Returns a procedure for writing the value of a particular field of a
member of the type represented by @var{rtd}.  The returned procedure
accepts exactly two arguments: first, a record of the appropriate type,
and second, an arbitrary Scheme value; it modifies the field named by
the symbol @var{field-name} in that record to contain the given value.
The returned value of the modifier procedure is unspecified.  The symbol
@var{field-name} must be a member of the list of field-names in the call
to @code{make-record-type} that created the type represented by
@var{rtd}.
@end defun

In May of 1996, as a product of discussion on the @code{rrrs-authors}
mailing list, I rewrote @file{record.scm} to portably implement type
disjointness for record data types.

As long as an implementation's procedures are opaque and the
@code{record} code is loaded before other programs, this will give
disjoint record types which are unforgeable and incorruptible by R4RS
procedures.

As a consequence, the procedures @code{record?},
@code{record-type-descriptor}, @code{record-type-name}.and
@code{record-type-field-names} are no longer supported.

@ignore
@defun record? obj
Returns a true value if @var{obj} is a record of any type and a false
value otherwise.  Note that @code{record?} may be true of any Scheme
value; of course, if it returns true for some particular value, then
@code{record-type-descriptor} is applicable to that value and returns an
appropriate descriptor.
@end defun

@defun record-type-descriptor record
Returns a record-type descriptor representing the type of the given
record.  That is, for example, if the returned descriptor were passed to
@code{record-predicate}, the resulting predicate would return a true
value when passed the given record.  Note that it is not necessarily the
case that the returned descriptor is the one that was passed to
@code{record-constructor} in the call that created the constructor
procedure that created the given record.
@end defun

@defun record-type-name rtd
Returns the type-name associated with the type represented by rtd.  The
returned value is @code{eqv?} to the @var{type-name} argument given in
the call to @code{make-record-type} that created the type represented by
@var{rtd}.
@end defun

@defun record-type-field-names rtd
Returns a list of the symbols naming the fields in members of the type
represented by @var{rtd}.  The returned value is @code{equal?} to the
field-names argument given in the call to @code{make-record-type} that
created the type represented by @var{rtd}.
@end defun
@end ignore


@node Sorting and Searching, Procedures, Data Structures, Other Packages
@section Sorting and Searching

@menu
* Common List Functions::       'common-list-functions
* Tree Operations::             'tree
* Chapter Ordering::            'chapter-order
* Sorting::                     'sort
* Topological Sort::            Keep your socks on.
* Hashing::                     'hash
* Space-Filling Curves::        'space-filling and 'sierpinski
* Soundex::                     Dimension Reduction of Last Names
* String Search::               Also Search from a Port.
* Sequence Comparison::         'diff and longest-common-subsequence
@end menu

@node Common List Functions, Tree Operations, Sorting and Searching, Sorting and Searching
@subsection Common List Functions

@code{(require 'common-list-functions)}
@ftindex common-list-functions

The procedures below follow the Common LISP equivalents apart from
optional arguments in some cases.

@menu
* List construction::           
* Lists as sets::               
* Lists as sequences::          
* Destructive list operations::  
* Non-List functions::          
@end menu

@node List construction, Lists as sets, Common List Functions, Common List Functions
@subsubsection List construction

@defun make-list k
@defunx make-list k init
@code{make-list} creates and returns a list of @var{k} elements.  If
@var{init} is included, all elements in the list are initialized to
@var{init}.

Example:
@lisp
(make-list 3)
   @result{} (#<unspecified> #<unspecified> #<unspecified>)
(make-list 5 'foo)
   @result{} (foo foo foo foo foo)
@end lisp
@end defun


@defun list* obj1 obj2 @dots{}
Works like @code{list} except that the cdr of the last pair is the last
argument unless there is only one argument, when the result is just that
argument.  Sometimes called @code{cons*}.  E.g.:

@lisp
(list* 1)
   @result{} 1
(list* 1 2 3)
   @result{} (1 2 . 3)
(list* 1 2 '(3 4))
   @result{} (1 2 3 4)
(list* @var{args} '())
   @equiv{} (list @var{args})
@end lisp
@end defun

@defun copy-list lst
@code{copy-list} makes a copy of @var{lst} using new pairs and returns
it. Only the top level of the list is copied, i.e., pairs forming
elements of the copied list remain @code{eq?} to the corresponding
elements of the original; the copy is, however, not @code{eq?} to the
original, but is @code{equal?} to it.

Example:
@lisp
(copy-list '(foo foo foo))
   @result{} (foo foo foo)
(define q '(foo bar baz bang))
(define p q)
(eq? p q)
   @result{} #t
(define r (copy-list q))
(eq? q r)
   @result{} #f
(equal? q r)
   @result{} #t
(define bar '(bar))
(eq? bar (car (copy-list (list bar 'foo))))
@result{} #t
   @end lisp
@end defun


@node Lists as sets, Lists as sequences, List construction, Common List Functions
@subsubsection Lists as sets

@code{eqv?} is used to test for membership by procedures which treat
lists as sets.

@defun adjoin e l
@code{adjoin} returns the adjoint of the element @var{e} and the list
@var{l}.  That is, if @var{e} is in @var{l}, @code{adjoin} returns
@var{l}, otherwise, it returns @code{(cons @var{e} @var{l})}.

Example:
@lisp
(adjoin 'baz '(bar baz bang))
   @result{} (bar baz bang)
(adjoin 'foo '(bar baz bang))
   @result{} (foo bar baz bang)
@end lisp
@end defun

@defun union l1 l2
@code{union} returns a list of all elements that are in @var{l1} or
@var{l2}.  Duplicates between @var{l1} and @var{l2} are culled.
Duplicates within @var{l1} or within @var{l2} may or may not be
removed.

Example:
@lisp
(union '(1 2 3 4) '(5 6 7 8))
   @result{} (1 2 3 4 5 6 7 8)
(union '(0 1 2 3 4) '(3 4 5 6))
   @result{} (5 6 0 1 2 3 4)
@end lisp
@end defun

@defun intersection l1 l2
@code{intersection} returns a list of all elements that are in both
@var{l1} and @var{l2}.

Example:
@lisp
(intersection '(1 2 3 4) '(3 4 5 6))
   @result{} (3 4)
(intersection '(1 2 3 4) '(5 6 7 8))
   @result{} ()
@end lisp
@end defun

@defun set-difference l1 l2
@code{set-difference} returns a list of all elements that are in
@var{l1} but not in @var{l2}.

Example:
@lisp
(set-difference '(1 2 3 4) '(3 4 5 6))
   @result{} (1 2)
(set-difference '(1 2 3 4) '(1 2 3 4 5 6))
   @result{} ()
@end lisp
@end defun

@defun subset? list1 list2
Returns @code{#t} if every element of @var{list1} is @code{eqv?} an
element of @var{list2}; otherwise returns @code{#f}.

Example:
@lisp
(subset? '(1 2 3 4) '(3 4 5 6))
   @result{} #f
(subset? '(1 2 3 4) '(6 5 4 3 2 1 0))
   @result{} #t
@end lisp
@end defun

@defun member-if pred lst
@code{member-if} returns the list headed by the first element of
@var{lst} to satisfy @code{(@var{pred} @var{element})}.
@code{Member-if} returns @code{#f} if @var{pred} returns @code{#f} for
every @var{element} in @var{lst}.

Example:
@lisp
(member-if vector? '(a 2 b 4))
   @result{} #f
(member-if number? '(a 2 b 4))
   @result{} (2 b 4)
@end lisp
@end defun

@defun some pred lst1 lst2 @dots{}
@var{pred} is a boolean function of as many arguments as there are list
arguments to @code{some} i.e., @var{lst} plus any optional arguments.
@var{pred} is applied to successive elements of the list arguments in
order.  @code{some} returns @code{#t} as soon as one of these
applications returns @code{#t}, and is @code{#f} if none returns
@code{#t}.  All the lists should have the same length.


Example:
@lisp
(some odd? '(1 2 3 4))
   @result{} #t

(some odd? '(2 4 6 8))
   @result{} #f

(some > '(1 3) '(2 4))
   @result{} #f
@end lisp
@end defun

@defun every pred lst1 lst2 @dots{}
@code{every} is analogous to @code{some} except it returns @code{#t} if
every application of @var{pred} is @code{#t} and @code{#f}
otherwise.

Example:
@lisp
(every even? '(1 2 3 4))
   @result{} #f

(every even? '(2 4 6 8))
   @result{} #t

(every > '(2 3) '(1 4))
   @result{} #f
@end lisp
@end defun

@defun notany pred lst1 @dots{}
@code{notany} is analogous to @code{some} but returns @code{#t} if no
application of @var{pred} returns @code{#t} or @code{#f} as soon as any
one does.
@end defun

@defun notevery pred lst1 @dots{}
@code{notevery} is analogous to @code{some} but returns @code{#t} as soon
as an application of @var{pred} returns @code{#f}, and @code{#f}
otherwise.

Example:
@lisp
(notevery even? '(1 2 3 4))
   @result{} #t

(notevery even? '(2 4 6 8))
   @result{} #f
@end lisp
@end defun


@defun list-of?? predicate
Returns a predicate which returns true if its argument is a list every
element of which satisfies @var{predicate}.
@end defun

@defun list-of?? predicate low-bound high-bound
@var{low-bound} and @var{high-bound} are non-negative integers.
@code{list-of??} returns a predicate which returns true if its argument
is a list of length between @var{low-bound} and @var{high-bound}
(inclusive); every element of which satisfies @var{predicate}.
@end defun

@defun list-of?? predicate bound
@var{bound} is an integer.  If @var{bound} is negative, @code{list-of??}
returns a predicate which returns true if its argument is a list of
length greater than @code{(- @var{bound})}; every element of which
satisfies @var{predicate}.  Otherwise, @code{list-of??}  returns a
predicate which returns true if its argument is a list of length less
than or equal to @var{bound}; every element of which satisfies
@var{predicate}.
@end defun


@defun find-if pred lst
@code{find-if} searches for the first @var{element} in @var{lst} such
that @code{(@var{pred} @var{element})} returns @code{#t}.  If it finds
any such @var{element} in @var{lst}, @var{element} is returned.
Otherwise, @code{#f} is returned.

Example:
@lisp
(find-if number? '(foo 1 bar 2))
   @result{} 1

(find-if number? '(foo bar baz bang))
   @result{} #f

(find-if symbol? '(1 2 foo bar))
   @result{} foo
@end lisp
@end defun

@defun remove elt lst
@code{remove} removes all occurrences of @var{elt} from @var{lst} using
@code{eqv?} to test for equality and returns everything that's left.
N.B.: other implementations (Chez, Scheme->C and T, at least) use
@code{equal?} as the equality test.

Example:
@lisp
(remove 1 '(1 2 1 3 1 4 1 5))
   @result{} (2 3 4 5)

(remove 'foo '(bar baz bang))
   @result{} (bar baz bang)
@end lisp
@end defun

@defun remove-if pred lst
@code{remove-if} removes all @var{element}s from @var{lst} where
@code{(@var{pred} @var{element})} is @code{#t} and returns everything
that's left.

Example:
@lisp
(remove-if number? '(1 2 3 4))
   @result{} ()

(remove-if even? '(1 2 3 4 5 6 7 8))
   @result{} (1 3 5 7)
@end lisp
@end defun

@defun remove-if-not pred lst
@code{remove-if-not} removes all @var{element}s from @var{lst} for which
@code{(@var{pred} @var{element})} is @code{#f} and returns everything that's
left.

Example:
@lisp
(remove-if-not number? '(foo bar baz))
   @result{} ()
(remove-if-not odd? '(1 2 3 4 5 6 7 8))
   @result{} (1 3 5 7)
@end lisp
@end defun

@defun has-duplicates? lst
returns @code{#t} if 2 members of @var{lst} are @code{equal?}, @code{#f}
otherwise.

Example:
@lisp
(has-duplicates? '(1 2 3 4))
   @result{} #f

(has-duplicates? '(2 4 3 4))
   @result{} #t
@end lisp
@end defun

The procedure @code{remove-duplicates} uses @code{member} (rather than
@code{memv}).

@defun remove-duplicates lst
returns a copy of @var{lst} with its duplicate members removed.
Elements are considered duplicate if they are @code{equal?}.

Example:
@lisp
(remove-duplicates '(1 2 3 4))
   @result{} (1 2 3 4)

(remove-duplicates '(2 4 3 4))
   @result{} (2 4 3)
@end lisp
@end defun


@node Lists as sequences, Destructive list operations, Lists as sets, Common List Functions
@subsubsection Lists as sequences

@defun position obj lst
@code{position} returns the 0-based position of @var{obj} in @var{lst},
or @code{#f} if @var{obj} does not occur in @var{lst}.

Example:
@lisp
(position 'foo '(foo bar baz bang))
   @result{} 0
(position 'baz '(foo bar baz bang))
   @result{} 2
(position 'oops '(foo bar baz bang))
   @result{} #f
@end lisp
@end defun

@defun reduce p lst
@code{reduce} combines all the elements of a sequence using a binary
operation (the combination is left-associative).  For example, using
@code{+}, one can add up all the elements.  @code{reduce} allows you to
apply a function which accepts only two arguments to more than 2
objects.  Functional programmers usually refer to this as @dfn{foldl}.
@code{collect:reduce} (@pxref{Collections}) provides a version of
@code{collect} generalized to collections.

Example:
@lisp
(reduce + '(1 2 3 4))
   @result{} 10
(define (bad-sum . l) (reduce + l))
(bad-sum 1 2 3 4)
   @equiv{} (reduce + (1 2 3 4))
   @equiv{} (+ (+ (+ 1 2) 3) 4)
@result{} 10
(bad-sum)
   @equiv{} (reduce + ())
   @result{} ()
(reduce string-append '("hello" "cruel" "world"))
   @equiv{} (string-append (string-append "hello" "cruel") "world")
   @result{} "hellocruelworld"
(reduce anything '())
   @result{} ()
(reduce anything '(x))
   @result{} x
@end lisp

What follows is a rather non-standard implementation of @code{reverse}
in terms of @code{reduce} and a combinator elsewhere called
@dfn{C}.

@lisp
;;; Contributed by Jussi Piitulainen (jpiitula @@ ling.helsinki.fi)

(define commute
  (lambda (f)
    (lambda (x y)
      (f y x))))

(define reverse
  (lambda (args)
    (reduce-init (commute cons) '() args)))
@end lisp
@end defun

@defun reduce-init p init lst
@code{reduce-init} is the same as reduce, except that it implicitly
inserts @var{init} at the start of the list.  @code{reduce-init} is
preferred if you want to handle the null list, the one-element, and
lists with two or more elements consistently.  It is common to use the
operator's idempotent as the initializer.  Functional programmers
usually call this @dfn{foldl}.

Example:
@lisp
(define (sum . l) (reduce-init + 0 l))
(sum 1 2 3 4)
   @equiv{} (reduce-init + 0 (1 2 3 4))
   @equiv{} (+ (+ (+ (+ 0 1) 2) 3) 4)
   @result{} 10
(sum)
   @equiv{} (reduce-init + 0 '())
   @result{} 0

(reduce-init string-append "@@" '("hello" "cruel" "world"))
@equiv{}
(string-append (string-append (string-append "@@" "hello")
                               "cruel")
               "world")
@result{} "@@hellocruelworld"
@end lisp

Given a differentiation of 2 arguments, @code{diff}, the following will
differentiate by any number of variables.
@lisp
(define (diff* exp . vars)
  (reduce-init diff exp vars))
@end lisp

Example:
@lisp
;;; Real-world example:  Insertion sort using reduce-init.

(define (insert l item)
  (if (null? l)
      (list item)
      (if (< (car l) item)
          (cons (car l) (insert (cdr l) item))
          (cons item l))))
(define (insertion-sort l) (reduce-init insert '() l))

(insertion-sort '(3 1 4 1 5)
   @equiv{} (reduce-init insert () (3 1 4 1 5))
   @equiv{} (insert (insert (insert (insert (insert () 3) 1) 4) 1) 5)
   @equiv{} (insert (insert (insert (insert (3)) 1) 4) 1) 5)
   @equiv{} (insert (insert (insert (1 3) 4) 1) 5)
   @equiv{} (insert (insert (1 3 4) 1) 5)
   @equiv{} (insert (1 1 3 4) 5)
   @result{} (1 1 3 4 5)
   @end lisp
@end defun

@defun last lst n
@code{last} returns the last @var{n} elements of @var{lst}.  @var{n}
must be a non-negative integer.

Example:
@lisp
(last '(foo bar baz bang) 2)
   @result{} (baz bang)
(last '(1 2 3) 0)
   @result{} ()
@end lisp
@end defun

@defun butlast lst n
@code{butlast} returns all but the last @var{n} elements of
@var{lst}.

Example:
@lisp
(butlast '(a b c d) 3)
   @result{} (a)
(butlast '(a b c d) 4)
   @result{} ()
@end lisp
@end defun

@noindent
@code{last} and @code{butlast} split a list into two parts when given
identical arguments.
@example
(last '(a b c d e) 2)
   @result{} (d e)
(butlast '(a b c d e) 2)
   @result{} (a b c)
@end example

@defun nthcdr n lst
@code{nthcdr} takes @var{n} @code{cdr}s of @var{lst} and returns the
result.  Thus @code{(nthcdr 3 @var{lst})} @equiv{} @code{(cdddr
@var{lst})}

Example:
@lisp
(nthcdr 2 '(a b c d))
   @result{} (c d)
(nthcdr 0 '(a b c d))
   @result{} (a b c d)
@end lisp
@end defun

@defun butnthcdr n lst
@code{butnthcdr} returns all but the nthcdr @var{n} elements of
@var{lst}.

Example:
@lisp
(butnthcdr 3 '(a b c d))
   @result{} (a b c)
(butnthcdr 4 '(a b c d))
   @result{} (a b c d)
@end lisp
@end defun

@noindent
@code{nthcdr} and @code{butnthcdr} split a list into two parts when
given identical arguments.
@example
(nthcdr 2 '(a b c d e))
   @result{} (c d e)
(butnthcdr 2 '(a b c d e))
   @result{} (a b)
@end example

@defun butnth n lst
@code{butnth} returns a list of all but the nth element of @var{lst}.

Example:
@lisp
(butnth 2 '(a b c d))
   @result{} (a b d)
(butnth 4 '(a b c d))
   @result{} (a b c d)
@end lisp
@end defun

@node Destructive list operations, Non-List functions, Lists as sequences, Common List Functions
@subsubsection Destructive list operations

These procedures may mutate the list they operate on, but any such
mutation is undefined.

@deffn {Procedure} nconc args
@code{nconc} destructively concatenates its arguments.  (Compare this
with @code{append}, which copies arguments rather than destroying them.)
Sometimes called @code{append!} (@pxref{Rev2 Procedures}).

Example:  You want to find the subsets of a set.  Here's the obvious way:

@lisp
(define (subsets set)
  (if (null? set)
      '(())
      (append (map (lambda (sub) (cons (car set) sub))
                   (subsets (cdr set)))
              (subsets (cdr set)))))
@end lisp
But that does way more consing than you need.  Instead, you could
replace the @code{append} with @code{nconc}, since you don't have any
need for all the intermediate results.

Example:
@lisp
(define x '(a b c))
(define y '(d e f))
(nconc x y)
   @result{} (a b c d e f)
x
   @result{} (a b c d e f)
@end lisp

@code{nconc} is the same as @code{append!} in @file{sc2.scm}.
@end deffn

@deffn {Procedure} nreverse lst
@code{nreverse} reverses the order of elements in @var{lst} by mutating
@code{cdr}s of the list.  Sometimes called @code{reverse!}.

Example:
@lisp
(define foo '(a b c))
(nreverse foo)
   @result{} (c b a)
foo
   @result{} (a)
@end lisp

Some people have been confused about how to use @code{nreverse},
thinking that it doesn't return a value.  It needs to be pointed out
that

@lisp
(set! lst (nreverse lst))
@end lisp
@noindent
is the proper usage, not
@lisp
(nreverse lst)
@end lisp
The example should suffice to show why this is the case.
@end deffn

@deffn {Procedure} delete elt lst
@deffnx {Procedure} delete-if pred lst
@deffnx {Procedure} delete-if-not pred lst
Destructive versions of @code{remove} @code{remove-if}, and
@code{remove-if-not}.

Example:
@lisp
(define lst (list 'foo 'bar 'baz 'bang))
(delete 'foo lst)
   @result{} (bar baz bang)
lst
   @result{} (foo bar baz bang)

(define lst (list 1 2 3 4 5 6 7 8 9))
(delete-if odd? lst)
   @result{} (2 4 6 8)
lst
   @result{} (1 2 4 6 8)
@end lisp

Some people have been confused about how to use @code{delete},
@code{delete-if}, and @code{delete-if}, thinking that they don't return
a value.  It needs to be pointed out that

@lisp
(set! lst (delete el lst))
@end lisp
@noindent
is the proper usage, not
@lisp
(delete el lst)
@end lisp
The examples should suffice to show why this is the case.
@end deffn


@node Non-List functions,  , Destructive list operations, Common List Functions
@subsubsection Non-List functions

@defun and? arg1 @dots{}
@code{and?} checks to see if all its arguments are true.  If they are,
@code{and?} returns @code{#t}, otherwise, @code{#f}.  (In contrast to
@code{and}, this is a function, so all arguments are always evaluated
and in an unspecified order.)

Example:
@lisp
(and? 1 2 3)
   @result{} #t
(and #f 1 2)
   @result{} #f
@end lisp
@end defun

@defun or? arg1 @dots{}
@code{or?} checks to see if any of its arguments are true.  If any is
true, @code{or?} returns @code{#t}, and @code{#f} otherwise.  (To
@code{or} as @code{and?} is to @code{and}.)

Example:
@lisp
(or? 1 2 #f)
   @result{} #t
(or? #f #f #f)
   @result{} #f
@end lisp
@end defun

@defun atom? object
Returns @code{#t} if @var{object} is not a pair and @code{#f} if it is
pair.  (Called @code{atom} in Common LISP.)
@lisp
(atom? 1)
   @result{} #t
(atom? '(1 2))
   @result{} #f
(atom? #(1 2))   ; dubious!
   @result{} #t
@end lisp
@end defun


@node Tree Operations, Chapter Ordering, Common List Functions, Sorting and Searching
@subsection Tree operations

@include tree.txi


@node Chapter Ordering, Sorting, Tree Operations, Sorting and Searching
@subsection Chapter Ordering

@include chap.txi


@node Sorting, Topological Sort, Chapter Ordering, Sorting and Searching
@subsection Sorting

@code{(require 'sort)} or @code{(require 'srfi-95)}
@ftindex sort
@ftindex srfi-95

[by Richard A. O'Keefe, 1991]

I am providing this source code with no restrictions at all on its use
(but please retain D.H.D.Warren's credit for the original idea).

The code of @code{merge} and @code{merge!} could have been quite a bit
simpler, but they have been coded to reduce the amount of work done per
iteration.  (For example, we only have one @code{null?} test per
iteration.)

I gave serious consideration to producing Common-LISP-compatible
functions.  However, Common LISP's @code{sort} is our @code{sort!}
(well, in fact Common LISP's @code{stable-sort} is our @code{sort!};
merge sort is @emph{fast} as well as stable!) so adapting CL code to
Scheme takes a bit of work anyway.  I did, however, appeal to CL to
determine the @emph{order} of the arguments.

The standard functions @code{<}, @code{>}, @code{char<?}, @code{char>?},
@code{char-ci<?}, @code{char-ci>?}, @code{string<?}, @code{string>?},
@code{string-ci<?}, and @code{string-ci>?} are suitable for use as
comparison functions.  Think of @code{(less? x y)} as saying when
@code{x} must @emph{not} precede @code{y}.

[Addendum by Aubrey Jaffer, 2006]

These procedures are stable when called with predicates which return
@code{#f} when applied to identical arguments.

The @code{sorted?}, @code{merge}, and @code{merge!} procedures consume
asymptotic time and space no larger than @i{O(N)}, where @i{N} is the
sum of the lengths of the sequence arguments.
The @code{sort} and @code{sort!} procedures consume asymptotic time
and space no larger than @i{O(N*log(N))}, where @i{N} is the length of
the sequence argument.

All five functions take an optional @var{key} argument corresponding
to a CL-style @samp{&key} argument.  A @var{less?}  predicate with a
@var{key} argument behaves like:

@lisp
(lambda (x y) (@var{less?} (@var{key} x) (@var{key} y)))
@end lisp

All five functions will call the @var{key} argument at most once per
element.

The @samp{!} variants sort in place; @code{sort!} returns its
@var{sequence} argument.

@defun sorted? sequence less?
@defunx sorted? sequence less? key
Returns @code{#t} when the sequence argument is in non-decreasing
order according to @var{less?} (that is, there is no adjacent pair
@code{@dots{} x y @dots{}} for which @code{(less? y x)}).

Returns @code{#f} when the sequence contains at least one out-of-order
pair.  It is an error if the sequence is not a list or array
(including vectors and strings).
@end defun

@defun merge list1 list2 less?
@defunx merge list1 list2 less? key
Merges two sorted lists, returning a freshly allocated list as its
result.
@end defun

@defun merge! list1 list2 less?
@defunx merge! list1 list2 less? key
Merges two sorted lists, re-using the pairs of @var{list1} and
@var{list2} to build the result.  The result will be either
@var{list1} or @var{list2}.
@end defun

@defun sort sequence less?
@defunx sort sequence less? key
Accepts a list or array (including vectors and strings) for
@var{sequence}; and returns a completely new sequence which is sorted
according to @var{less?}.  The returned sequence is the same type as
the argument @var{sequence}.  Given valid arguments, it is always the
case that:

@lisp
(sorted? (sort @var{sequence} @var{less?}) @var{less?}) @result{} #t
@end lisp
@end defun

@defun sort! sequence less?
@defunx sort! sequence less? key
Returns list, array, vector, or string @var{sequence} which has been
mutated to order its elements according to @var{less?}.  Given valid
arguments, it is always the case that:

@lisp
(sorted? (sort! @var{sequence} @var{less?}) @var{less?}) @result{} #t
@end lisp
@end defun


@node Topological Sort, Hashing, Sorting, Sorting and Searching
@subsection Topological Sort

@include tsort.txi


@node Hashing, Space-Filling Curves, Topological Sort, Sorting and Searching
@subsection Hashing

@code{(require 'hash)}
@ftindex hash

These hashing functions are for use in quickly classifying objects.
Hash tables use these functions.

@defun hashq obj k
@defunx hashv obj k
@defunx hash obj k
Returns an exact non-negative integer less than @var{k}.  For each
non-negative integer less than @var{k} there are arguments @var{obj} for
which the hashing functions applied to @var{obj} and @var{k} returns
that integer.

For @code{hashq}, @code{(eq? obj1 obj2)} implies @code{(= (hashq obj1 k)
(hashq obj2))}.

For @code{hashv}, @code{(eqv? obj1 obj2)} implies @code{(= (hashv obj1 k)
(hashv obj2))}.

For @code{hash}, @code{(equal? obj1 obj2)} implies @code{(= (hash obj1 k)
(hash obj2))}.

@code{hash}, @code{hashv}, and @code{hashq} return in time bounded by a
constant.  Notice that items having the same @code{hash} implies the
items have the same @code{hashv} implies the items have the same
@code{hashq}.
@end defun


@node Space-Filling Curves, Soundex, Hashing, Sorting and Searching
@subsection Space-Filling Curves

@menu
* Multidimensional Space-Filling Curves::  Includes Hilbert and Peano curves
* Hilbert Space-Filling Curve::  Legacy
* Peano Space-Filling Curve::   Legacy
* Sierpinski Curve::            Rank-2 to scalar
@end menu

@node Multidimensional Space-Filling Curves, Hilbert Space-Filling Curve, Space-Filling Curves, Space-Filling Curves
@subsubsection Multidimensional Space-Filling Curves

@include rmdsff.txi


@node Hilbert Space-Filling Curve, Peano Space-Filling Curve, Multidimensional Space-Filling Curves, Space-Filling Curves
@subsubsection Hilbert Space-Filling Curve

@include phil-spc.txi


@node Peano Space-Filling Curve, Sierpinski Curve, Hilbert Space-Filling Curve, Space-Filling Curves
@subsubsection Peano Space-Filling Curve

@include peanosfc.txi


@node Sierpinski Curve,  , Peano Space-Filling Curve, Space-Filling Curves
@subsubsection Sierpinski Curve

@code{(require 'sierpinski)}
@ftindex sierpinski

@defun make-sierpinski-indexer max-coordinate
Returns a procedure (eg hash-function) of 2 numeric arguments which
preserves @emph{nearness} in its mapping from NxN to N.

@var{max-coordinate} is the maximum coordinate (a positive integer) of a
population of points.  The returned procedures is a function that takes
the x and y coordinates of a point, (non-negative integers) and returns
an integer corresponding to the relative position of that point along a
Sierpinski curve.  (You can think of this as computing a (pseudo-)
inverse of the Sierpinski spacefilling curve.)

Example use: Make an indexer (hash-function) for integer points lying in
square of integer grid points [0,99]x[0,99]:
@example
(define space-key (make-sierpinski-indexer 100))
@end example
Now let's compute the index of some points:
@example
(space-key 24 78)               @result{} 9206
(space-key 23 80)               @result{} 9172
@end example

Note that locations (24, 78) and (23, 80) are near in index and
therefore, because the Sierpinski spacefilling curve is continuous, we
know they must also be near in the plane.  Nearness in the plane does
not, however, necessarily correspond to nearness in index, although it
@emph{tends} to be so.

Example applications:
@itemize @bullet

@item
Sort points by Sierpinski index to get heuristic solution to
@emph{travelling salesman problem}.  For details of performance,
see L. Platzman and J. Bartholdi, "Spacefilling curves and the
Euclidean travelling salesman problem", JACM 36(4):719--737
(October 1989) and references therein.

@item
Use Sierpinski index as key by which to store 2-dimensional data
in a 1-dimensional data structure (such as a table).  Then
locations that are near each other in 2-d space will tend to
be near each other in 1-d data structure; and locations that
are near in 1-d data structure will be near in 2-d space.  This
can significantly speed retrieval from secondary storage because
contiguous regions in the plane will tend to correspond to
contiguous regions in secondary storage.  (This is a standard
technique for managing CAD/CAM or geographic data.)

@end itemize
@end defun


@node Soundex, String Search, Space-Filling Curves, Sorting and Searching
@subsection Soundex

@code{(require 'soundex)}
@ftindex soundex

@defun soundex name
Computes the @emph{soundex} hash of @var{name}.  Returns a string of an
initial letter and up to three digits between 0 and 6.  Soundex
supposedly has the property that names that sound similar in normal
English pronunciation tend to map to the same key.

Soundex was a classic algorithm used for manual filing of personal
records before the advent of computers.  It performs adequately for
English names but has trouble with other languages.

See Knuth, Vol. 3 @cite{Sorting and searching}, pp 391--2

To manage unusual inputs, @code{soundex} omits all non-alphabetic
characters.  Consequently, in this implementation:

@example
(soundex <string of blanks>)    @result{} ""
(soundex "")                    @result{} ""
@end example

Examples from Knuth:

@example
(map soundex '("Euler" "Gauss" "Hilbert" "Knuth"
                       "Lloyd" "Lukasiewicz"))
        @result{} ("E460" "G200" "H416" "K530" "L300" "L222")

(map soundex '("Ellery" "Ghosh" "Heilbronn" "Kant"
                        "Ladd" "Lissajous"))
        @result{} ("E460" "G200" "H416" "K530" "L300" "L222")
@end example

Some cases in which the algorithm fails (Knuth):

@example
(map soundex '("Rogers" "Rodgers"))     @result{} ("R262" "R326")

(map soundex '("Sinclair" "St. Clair")) @result{} ("S524" "S324")

(map soundex '("Tchebysheff" "Chebyshev")) @result{} ("T212" "C121")
@end example
@end defun


@node String Search, Sequence Comparison, Soundex, Sorting and Searching
@subsection String Search

@code{(require 'string-search)}
@ftindex string-search

@deffn {Procedure} string-index string char
@deffnx {Procedure} string-index-ci string char
Returns the index of the first occurence of @var{char} within
@var{string}, or @code{#f} if the @var{string} does not contain a
character @var{char}.
@end deffn

@deffn {Procedure} string-reverse-index string char
@deffnx {Procedure} string-reverse-index-ci string char
Returns the index of the last occurence of @var{char} within
@var{string}, or @code{#f} if the @var{string} does not contain a
character @var{char}.
@end deffn

@deffn {Procedure} substring? pattern string
@deffnx {Procedure} substring-ci? pattern string
Searches @var{string} to see if some substring of @var{string} is equal
to @var{pattern}.  @code{substring?} returns the index of the first
character of the first substring of @var{string} that is equal to
@var{pattern}; or @code{#f} if @var{string} does not contain
@var{pattern}.

@example
(substring? "rat" "pirate") @result{}  2
(substring? "rat" "outrage") @result{}  #f
(substring? "" any-string) @result{}  0
@end example
@end deffn

@deffn {Procedure} find-string-from-port? str in-port max-no-chars
Looks for a string @var{str} within the first @var{max-no-chars} chars
of the input port @var{in-port}.
@end deffn

@deffn {Procedure} find-string-from-port? str in-port
When called with two arguments, the search span is limited by the end of
the input stream.
@end deffn

@deffn {Procedure} find-string-from-port? str in-port char
Searches up to the first occurrence of character @var{char} in
@var{str}.
@end deffn

@deffn {Procedure} find-string-from-port? str in-port proc
Searches up to the first occurrence of the procedure @var{proc}
returning non-false when called with a character (from @var{in-port})
argument.

When the @var{str} is found, @code{find-string-from-port?} returns the
number of characters it has read from the port, and the port is set to
read the first char after that (that is, after the @var{str}) The
function returns @code{#f} when the @var{str} isn't found.

@code{find-string-from-port?} reads the port @emph{strictly}
sequentially, and does not perform any buffering.  So
@code{find-string-from-port?} can be used even if the @var{in-port} is
open to a pipe or other communication channel.
@end deffn

@defun string-subst txt old1 new1 @dots{}
Returns a copy of string @var{txt} with all occurrences of string
@var{old1} in @var{txt} replaced with @var{new1}; then @var{old2}
replaced with @var{new2} @dots{}.  Matches are found from the left.
Matches do not overlap.
@end defun

@defun count-newlines str
Returns the number of @samp{#\newline} characters in string @var{str}.
@end defun


@node Sequence Comparison,  , String Search, Sorting and Searching
@subsection Sequence Comparison

@code{(require 'diff)}
@ftindex diff
@cindex Sequence Comparison

@include differ.txi


@node Procedures, Standards Support, Sorting and Searching, Other Packages
@section Procedures

Anything that doesn't fall neatly into any of the other categories winds
up here.

@menu
* Type Coercion::               'coerce
* String-Case::                 'string-case
* String Ports::                'string-port
* Line I/O::                    'line-i/o
* Multi-Processing::            'process
* Metric Units::                Portable manifest types for numeric values.
@end menu

@node Type Coercion, String-Case, Procedures, Procedures
@subsection Type Coercion
@code{(require 'coerce)}
@ftindex coerce

@include coerce.txi


@node String-Case, String Ports, Type Coercion, Procedures
@subsection String-Case

@code{(require 'string-case)}
@ftindex string-case

@deffn {Procedure} string-upcase str
@deffnx {Procedure} string-downcase str
@deffnx {Procedure} string-capitalize str
The obvious string conversion routines.  These are non-destructive.
@end deffn

@defun string-upcase! str
@defunx string-downcase! str
@defunx string-capitalize! str
The destructive versions of the functions above.
@end defun

@defun string-ci->symbol str
Converts string @var{str} to a symbol having the same case as if the
symbol had been @code{read}.
@end defun

@defun symbol-append obj1 @dots{}
Converts @var{obj1} @dots{} to strings, appends them, and converts to a
symbol which is returned.  Strings and numbers are converted to read's
symbol case; the case of symbol characters is not changed.  #f is
converted to the empty string (symbol).
@end defun

@defun StudlyCapsExpand str delimiter
@defunx StudlyCapsExpand str
@var{delimiter} must be a string or character.  If absent,
@var{delimiter} defaults to @samp{-}.  @code{StudlyCapsExpand} returns a
copy of @var{str} where @var{delimiter} is inserted between each
lower-case character immediately followed by an upper-case character;
and between two upper-case characters immediately followed by a
lower-case character.

@example
(StudlyCapsExpand "aX" " ")   @result{} "a X"
(StudlyCapsExpand "aX" "..")  @result{} "a..X"
(StudlyCapsExpand "AX")       @result{} "AX"
(StudlyCapsExpand "Ax")       @result{} "Ax"
(StudlyCapsExpand "AXLE")     @result{} "AXLE"
(StudlyCapsExpand "aAXACz")   @result{} "a-AXA-Cz"
(StudlyCapsExpand "AaXACz")   @result{} "Aa-XA-Cz"
(StudlyCapsExpand "AAaXACz")  @result{} "A-Aa-XA-Cz"
(StudlyCapsExpand "AAaXAC")   @result{} "A-Aa-XAC"
@end example

@end defun


@node String Ports, Line I/O, String-Case, Procedures
@subsection String Ports

@code{(require 'string-port)}
@ftindex string-port

@deffn {Procedure} call-with-output-string proc
@var{proc} must be a procedure of one argument.  This procedure calls
@var{proc} with one argument: a (newly created) output port.  When the
function returns, the string composed of the characters written into the
port is returned.
@end deffn

@deffn {Procedure} call-with-input-string string proc
@var{proc} must be a procedure of one argument.  This procedure calls
@var{proc} with one argument: an (newly created) input port from which
@var{string}'s contents may be read.  When @var{proc} returns, the port
is closed and the value yielded by the procedure @var{proc} is
returned.
@end deffn


@node Line I/O, Multi-Processing, String Ports, Procedures
@subsection Line I/O

@code{(require 'line-i/o)}
@ftindex line-i

@include lineio.txi


@node Multi-Processing, Metric Units, Line I/O, Procedures
@subsection Multi-Processing

@code{(require 'process)}
@ftindex process

This module implements asynchronous (non-polled) time-sliced
multi-processing in the SCM Scheme implementation using procedures
@code{alarm} and @code{alarm-interrupt}.
@cindex alarm
@cindex alarm-interrupt
Until this is ported to another implementation, consider it an example
of writing schedulers in Scheme.

@deffn {Procedure} add-process! proc
Adds proc, which must be a procedure (or continuation) capable of
accepting accepting one argument, to the @code{process:queue}.  The
value returned is unspecified.  The argument to @var{proc} should be
ignored.  If @var{proc} returns, the process is killed.
@end deffn

@deffn {Procedure} process:schedule!
Saves the current process on @code{process:queue} and runs the next
process from @code{process:queue}.  The value returned is
unspecified.
@end deffn

@deffn {Procedure} kill-process!
Kills the current process and runs the next process from
@code{process:queue}.  If there are no more processes on
@code{process:queue}, @code{(slib:exit)} is called (@pxref{System}).
@end deffn


@node Metric Units,  , Multi-Processing, Procedures
@subsection Metric Units

@code{(require 'metric-units)}
@ftindex metric-units

@url{http://people.csail.mit.edu/jaffer/MIXF}

@dfn{Metric Interchange Format} is a character string encoding for
numerical values and units which:

@itemize @bullet
@item
is unambiguous in all locales;

@item
uses only [TOG] "Portable Character Set" characters matching "Basic
Latin" characters in Plane 0 of the Universal Character Set [UCS];

@item
is transparent to [UTF-7] and [UTF-8] UCS transformation formats;

@item
is human readable and writable;

@item
is machine readable and writable;

@item
incorporates SI prefixes and units;

@item
incorporates [ISO 6093] numbers; and

@item
incorporates [IEC 60027-2] binary prefixes.
@end itemize

In the expression for the value of a quantity, the unit symbol is placed
after the numerical value.  A dot (PERIOD, @samp{.}) is placed between
the numerical value and the unit symbol.

Within a compound unit, each of the base and derived symbols can
optionally have an attached SI prefix.

Unit symbols formed from other unit symbols by multiplication are
indicated by means of a dot (PERIOD, @samp{.}) placed between them.

Unit symbols formed from other unit symbols by division are indicated by
means of a SOLIDUS (@samp{/}) or negative exponents.  The SOLIDUS must
not be repeated in the same compound unit unless contained within a
parenthesized subexpression.

The grouping formed by a prefix symbol attached to a unit symbol
constitutes a new inseparable symbol (forming a multiple or submultiple
of the unit concerned) which can be raised to a positive or negative
power and which can be combined with other unit symbols to form compound
unit symbols.

The grouping formed by surrounding compound unit symbols with
parentheses (@samp{(} and @samp{)}) constitutes a new inseparable symbol
which can be raised to a positive or negative power and which can be
combined with other unit symbols to form compound unit symbols.

Compound prefix symbols, that is, prefix symbols formed by the
juxtaposition of two or more prefix symbols, are not permitted.

Prefix symbols are not used with the time-related unit symbols min
(minute), h (hour), d (day).  No prefix symbol may be used with dB
(decibel).  Only submultiple prefix symbols may be used with the unit
symbols L (liter), Np (neper), o (degree), oC (degree Celsius), rad
(radian), and sr (steradian).  Submultiple prefix symbols may not be
used with the unit symbols t (metric ton), r (revolution), or Bd (baud).

A unit exponent follows the unit, separated by a CIRCUMFLEX (@samp{^}).
Exponents may be positive or negative.  Fractional exponents must be
parenthesized.

@subsubsection SI Prefixes
@example
       Factor     Name    Symbol  |  Factor     Name    Symbol
       ======     ====    ======  |  ======     ====    ======
        1e24      yotta      Y    |   1e-1      deci       d
        1e21      zetta      Z    |   1e-2      centi      c
        1e18      exa        E    |   1e-3      milli      m
        1e15      peta       P    |   1e-6      micro      u
        1e12      tera       T    |   1e-9      nano       n
        1e9       giga       G    |   1e-12     pico       p
        1e6       mega       M    |   1e-15     femto      f
        1e3       kilo       k    |   1e-18     atto       a
        1e2       hecto      h    |   1e-21     zepto      z
        1e1       deka       da   |   1e-24     yocto      y
@end example

@subsubsection Binary Prefixes

These binary prefixes are valid only with the units B (byte) and bit.
However, decimal prefixes can also be used with bit; and decimal
multiple (not submultiple) prefixes can also be used with B (byte).

@example
                Factor       (power-of-2)  Name  Symbol
                ======       ============  ====  ======
       1.152921504606846976e18  (2^60)     exbi    Ei
          1.125899906842624e15  (2^50)     pebi    Pi
             1.099511627776e12  (2^40)     tebi    Ti
                1.073741824e9   (2^30)     gibi    Gi
                   1.048576e6   (2^20)     mebi    Mi
                      1.024e3   (2^10)     kibi    Ki
@end example

@subsubsection Unit Symbols

@example
    Type of Quantity      Name          Symbol   Equivalent
    ================      ====          ======   ==========
time                      second           s
time                      minute           min = 60.s
time                      hour             h   = 60.min
time                      day              d   = 24.h
frequency                 hertz            Hz    s^-1
signaling rate            baud             Bd    s^-1
length                    meter            m
volume                    liter            L     dm^3
plane angle               radian           rad
solid angle               steradian        sr    rad^2
plane angle               revolution     * r   = 6.283185307179586.rad
plane angle               degree         * o   = 2.777777777777778e-3.r
information capacity      bit              bit
information capacity      byte, octet      B   = 8.bit
mass                      gram             g
mass                      ton              t     Mg
mass              unified atomic mass unit u   = 1.66053873e-27.kg
amount of substance       mole             mol
catalytic activity        katal            kat   mol/s
thermodynamic temperature kelvin           K
centigrade temperature    degree Celsius   oC
luminous intensity        candela          cd
luminous flux             lumen            lm    cd.sr
illuminance               lux              lx    lm/m^2
force                     newton           N     m.kg.s^-2
pressure, stress          pascal           Pa    N/m^2
energy, work, heat        joule            J     N.m
energy                    electronvolt     eV  = 1.602176462e-19.J
power, radiant flux       watt             W     J/s
logarithm of power ratio  neper            Np
logarithm of power ratio  decibel        * dB  = 0.1151293.Np
electric current          ampere           A
electric charge           coulomb          C     s.A
electric potential, EMF   volt             V     W/A
capacitance               farad            F     C/V
electric resistance       ohm              Ohm   V/A
electric conductance      siemens          S     A/V
magnetic flux             weber            Wb    V.s
magnetic flux density     tesla            T     Wb/m^2
inductance                henry            H     Wb/A
radionuclide activity     becquerel        Bq    s^-1
absorbed dose energy      gray             Gy    m^2.s^-2
dose equivalent           sievert          Sv    m^2.s^-2
@end example

* The formulas are:

@itemize @bullet
@item
r/rad = 8 * atan(1)
@item
o/r = 1 / 360
@item
db/Np = ln(10) / 20
@end itemize

@defun si:conversion-factor to-unit from-unit
If the strings @var{from-unit} and @var{to-unit} express valid unit
expressions for quantities of the same unit-dimensions, then the value
returned by @code{si:conversion-factor} will be such that multiplying a
numerical value expressed in @var{from-unit}s by the returned conversion
factor yields the numerical value expressed in @var{to-unit}s.

Otherwise, @code{si:conversion-factor} returns:

@table @asis
@item -3
if neither @var{from-unit} nor @var{to-unit} is a syntactically valid
unit.
@item -2
if @var{from-unit} is not a syntactically valid unit.
@item -1
if @var{to-unit} is not a syntactically valid unit.
@item 0
if linear conversion (by a factor) is not possible.
@end table

@end defun

@example
(si:conversion-factor "km/s" "m/s" ) @result{} 0.001     
(si:conversion-factor "N"    "m/s" ) @result{} 0         
(si:conversion-factor "moC"  "oC"  ) @result{} 1000      
(si:conversion-factor "mK"   "oC"  ) @result{} 0         
(si:conversion-factor "rad"  "o"   ) @result{} 0.0174533 
(si:conversion-factor "K"    "o"   ) @result{} 0         
(si:conversion-factor "K"    "K"   ) @result{} 1         
(si:conversion-factor "oK"   "oK"  ) @result{} -3        
(si:conversion-factor ""     "s/s" ) @result{} 1         
(si:conversion-factor "km/h" "mph" ) @result{} -2        
@end example


@node Standards Support, Session Support, Procedures, Other Packages
@section Standards Support



@menu
* RnRS::                        Revised Reports on Scheme
* With-File::                   'with-file
* Transcripts::                 'transcript
* Rev2 Procedures::             'rev2-procedures
* Rev4 Optional Procedures::    'rev4-optional-procedures
* Multi-argument / and -::      'multiarg/and-
* Multi-argument Apply::        'multiarg-apply
* Rationalize::                 'rationalize
* Promises::                    'delay
* Dynamic-Wind::                'dynamic-wind
* Eval::                        'eval
* Values::                      'values
* SRFI::                        'http://srfi.schemers.org/srfi-0/srfi-0.html
@end menu

@node RnRS, With-File, Standards Support, Standards Support
@subsection RnRS

@noindent
The @code{r2rs}, @code{r3rs}, @code{r4rs}, and @code{r5rs} features
attempt to provide procedures and macros to bring a Scheme
implementation to the desired version of Scheme.

@deftp {Feature} r2rs
@ftindex r2rs
Requires features implementing procedures and optional procedures
specified by @cite{Revised^2 Report on the Algorithmic Language Scheme};
namely @code{rev3-procedures} and @code{rev2-procedures}.
@end deftp

@deftp {Feature} r3rs
@ftindex r3rs
Requires features implementing procedures and optional procedures
specified by @cite{Revised^3 Report on the Algorithmic Language Scheme};
namely @code{rev3-procedures}.

@emph{Note:} SLIB already mandates the @code{r3rs} procedures which can
be portably implemented in @code{r4rs} implementations.
@end deftp

@deftp {Feature} r4rs
@ftindex r4rs
Requires features implementing procedures and optional procedures
specified by @cite{Revised^4 Report on the Algorithmic Language Scheme};
namely @code{rev4-optional-procedures}.
@end deftp

@deftp {Feature} r5rs
@ftindex r5rs
Requires features implementing procedures and optional procedures
specified by @cite{Revised^5 Report on the Algorithmic Language Scheme};
namely @code{values}, @code{macro}, and @code{eval}.
@end deftp


@node With-File, Transcripts, RnRS, Standards Support
@subsection With-File

@code{(require 'with-file)}
@ftindex with-file

@defun with-input-from-file file thunk
@defunx with-output-to-file file thunk
Description found in R4RS.
@end defun


@node Transcripts, Rev2 Procedures, With-File, Standards Support
@subsection Transcripts

@code{(require 'transcript)}
@ftindex transcript

@defun transcript-on filename
@defunx transcript-off filename
Redefines @code{read-char}, @code{read}, @code{write-char},
@code{write}, @code{display}, and @code{newline}.
@end defun


@node Rev2 Procedures, Rev4 Optional Procedures, Transcripts, Standards Support
@subsection Rev2 Procedures

@code{(require 'rev2-procedures)}
@ftindex rev2-procedures

The procedures below were specified in the @cite{Revised^2 Report on
Scheme}.  @strong{N.B.}: The symbols @code{1+} and @code{-1+} are not
@cite{R4RS} syntax.  Scheme->C, for instance, chokes on this
module.

@deffn {Procedure} substring-move-left! string1 start1 end1 string2 start2
@deffnx {Procedure} substring-move-right! string1 start1 end1 string2 start2
@var{string1} and @var{string2} must be a strings, and @var{start1},
@var{start2} and @var{end1} must be exact integers satisfying

@display
0 <= @var{start1} <= @var{end1} <= (string-length @var{string1})
0 <= @var{start2} <= @var{end1} - @var{start1} + @var{start2} <= (string-length @var{string2})
@end display

@code{substring-move-left!} and @code{substring-move-right!} store
characters of @var{string1} beginning with index @var{start1}
(inclusive) and ending with index @var{end1} (exclusive) into
@var{string2} beginning with index @var{start2} (inclusive).

@code{substring-move-left!} stores characters in time order of
increasing indices.  @code{substring-move-right!} stores characters in
time order of increasing indeces.
@end deffn

@deffn {Procedure} substring-fill! string start end char
Fills the elements @var{start}--@var{end} of @var{string} with the
character @var{char}.
@end deffn

@defun string-null? str
@equiv{} @code{(= 0 (string-length @var{str}))}
@end defun

@deffn {Procedure} append! pair1 @dots{}
Destructively appends its arguments.  Equivalent to @code{nconc}.
@end deffn

@defun 1+ n
Adds 1 to @var{n}.
@end defun

@defun -1+ n
Subtracts 1 from @var{n}.
@end defun

@defun <?
@defunx <=?
@defunx =?
@defunx >?
@defunx >=?
These are equivalent to the procedures of the same name but without the
trailing @samp{?}.
@end defun


@node Rev4 Optional Procedures, Multi-argument / and -, Rev2 Procedures, Standards Support
@subsection Rev4 Optional Procedures

@code{(require 'rev4-optional-procedures)}
@ftindex rev4-optional-procedures

For the specification of these optional procedures,
@xref{Standard procedures, , ,r4rs, Revised(4) Scheme}.

@defun list-tail l p
@end defun

@defun string-copy
@end defun

@deffn {Procedure} string-fill! s obj
@end deffn

@deffn {Procedure} vector-fill! s obj
@end deffn


@node Multi-argument / and -, Multi-argument Apply, Rev4 Optional Procedures, Standards Support
@subsection Multi-argument / and -

@code{(require 'multiarg/and-)}
@ftindex multiarg

For the specification of these optional forms,
@xref{Numerical operations, , ,r4rs, Revised(4) Scheme}.

@defun / dividend divisor1 @dots{}
@end defun

@defun - minuend subtrahend1 @dots{}
@end defun


@node Multi-argument Apply, Rationalize, Multi-argument / and -, Standards Support
@subsection Multi-argument Apply

@code{(require 'multiarg-apply)}
@ftindex multiarg-apply

@noindent
For the specification of this optional form,
@xref{Control features, , ,r4rs, Revised(4) Scheme}.

@defun apply proc arg1 @dots{}
@end defun


@node Rationalize, Promises, Multi-argument Apply, Standards Support
@subsection Rationalize

@include ratize.txi


@node Promises, Dynamic-Wind, Rationalize, Standards Support
@subsection Promises

@code{(require 'promise)}
@ftindex promise

@defun make-promise proc
@end defun

@defun force promise
@end defun

@code{(require 'delay)} provides @code{force} and @code{delay}:

@defmac delay obj
Change occurrences of @code{(delay @var{expression})} to

@example
(make-promise (lambda () @var{expression}))
@end example

@end defmac

(@pxref{Control features, , ,r4rs, Revised(4) Scheme}).


@node Dynamic-Wind, Eval, Promises, Standards Support
@subsection Dynamic-Wind

@code{(require 'dynamic-wind)}
@ftindex dynamic-wind

This facility is a generalization of Common LISP @code{unwind-protect},
designed to take into account the fact that continuations produced by
@code{call-with-current-continuation} may be reentered.

@deffn {Procedure} dynamic-wind thunk1 thunk2 thunk3
The arguments @var{thunk1}, @var{thunk2}, and @var{thunk3} must all be
procedures of no arguments (thunks).

@code{dynamic-wind} calls @var{thunk1}, @var{thunk2}, and then
@var{thunk3}.  The value returned by @var{thunk2} is returned as the
result of @code{dynamic-wind}.  @var{thunk3} is also called just before
control leaves the dynamic context of @var{thunk2} by calling a
continuation created outside that context.  Furthermore, @var{thunk1} is
called before reentering the dynamic context of @var{thunk2} by calling
a continuation created inside that context.  (Control is inside the
context of @var{thunk2} if @var{thunk2} is on the current return stack).

@strong{Warning:} There is no provision for dealing with errors or
interrupts.  If an error or interrupt occurs while using
@code{dynamic-wind}, the dynamic environment will be that in effect at
the time of the error or interrupt.
@end deffn


@node Eval, Values, Dynamic-Wind, Standards Support
@subsection Eval

@code{(require 'eval)}
@ftindex eval

@defun eval expression environment-specifier

Evaluates @var{expression} in the specified environment and returns its
value.  @var{Expression} must be a valid Scheme expression represented
as data, and @var{environment-specifier} must be a value returned by one
of the three procedures described below.  Implementations may extend
@code{eval} to allow non-expression programs (definitions) as the first
argument and to allow other values as environments, with the restriction
that @code{eval} is not allowed to create new bindings in the
environments associated with @code{null-environment} or
@code{scheme-report-environment}.

@lisp
(eval '(* 7 3) (scheme-report-environment 5))
                                                   @result{}  21

(let ((f (eval '(lambda (f x) (f x x))
               (null-environment))))
  (f + 10))
                                                   @result{}  20
@end lisp
@end defun

@defun scheme-report-environment version
@defunx null-environment version
@defunx null-environment

@var{Version} must be an exact non-negative integer @var{n}
corresponding to a version of one of the Revised^@var{n} Reports on
Scheme.  @code{Scheme-report-environment} returns a specifier for an
environment that contains the set of bindings specified in the
corresponding report that the implementation supports.
@code{Null-environment} returns a specifier for an environment that
contains only the (syntactic) bindings for all the syntactic keywords
defined in the given version of the report.

Not all versions may be available in all implementations at all times.
However, an implementation that conforms to version @var{n} of the
Revised^@var{n} Reports on Scheme must accept version @var{n}.  An error
is signalled if the specified version is not available.

The effect of assigning (through the use of @code{eval}) a variable
bound in a @code{scheme-report-environment} (for example @code{car}) is
unspecified. Thus the environments specified by
@code{scheme-report-environment} may be immutable.

@end defun

@defun interaction-environment

This optional procedure returns a specifier for the environment that
contains implementation-defined bindings, typically a superset of those
listed in the report.  The intent is that this procedure will return the
environment in which the implementation would evaluate expressions
dynamically typed by the user.
@end defun

@noindent
Here are some more @code{eval} examples:

@example
(require 'eval)
@result{} #<unspecified>
(define car 'volvo)
@result{} #<unspecified>
car
@result{} volvo
(eval 'car (interaction-environment))
@result{} volvo
(eval 'car (scheme-report-environment 5))
@result{} #<primitive-procedure car>
(eval '(eval 'car (interaction-environment))
      (scheme-report-environment 5))
@result{} volvo
(eval '(eval '(set! car 'buick) (interaction-environment))
      (scheme-report-environment 5))
@result{} #<unspecified>
car
@result{} buick
(eval 'car (scheme-report-environment 5))
@result{} #<primitive-procedure car>
(eval '(eval 'car (interaction-environment))
      (scheme-report-environment 5))
@result{} buick
@end example


@node Values, SRFI, Eval, Standards Support
@subsection Values

@code{(require 'values)}
@ftindex values

@defun values obj @dots{}
@code{values} takes any number of arguments, and passes (returns) them
to its continuation.
@end defun


@defun call-with-values thunk proc
@var{thunk} must be a procedure of no arguments, and @var{proc} must be
a procedure.  @code{call-with-values} calls @var{thunk} with a
continuation that, when passed some values, calls @var{proc} with those
values as arguments.

Except for continuations created by the @code{call-with-values}
procedure, all continuations take exactly one value, as now; the effect
of passing no value or more than one value to continuations that were
not created by the @code{call-with-values} procedure is
unspecified.
@end defun


@node SRFI,  , Values, Standards Support
@subsection SRFI

@include srfi.txi

@menu
* SRFI-1::                      list-processing
@end menu

@itemize @bullet
@ftindex srfi-2
@item SRFI-2 @ref{Guarded LET* special form}
@ftindex srfi-8
@item SRFI-8 @ref{Binding to multiple values}
@ftindex srfi-9
@item SRFI-9 @ref{Define-Record-Type}
@ftindex srfi-11
@item SRFI-11 @ref{Binding to multiple values}
@ftindex srfi-23
@item SRFI-23 @code{(define error slib:error)}
@ftindex srfi-28
@item SRFI-28 @ref{Format}
@ftindex srfi-39
@item SRFI-39 @ref{Parameter Objects}
@ftindex srfi-47
@item SRFI-47 @ref{Arrays}
@ftindex srfi-59
@item SRFI-59 @ref{Vicinity}
@ftindex srfi-60
@item SRFI-60 @ref{Bit-Twiddling}
@ftindex srfi-61
@item SRFI-61 @ref{Guarded COND Clause}
@ftindex srfi-63
@item SRFI-63 @ref{Arrays}
@ftindex srfi-94
@item SRFI-94 @ref{Irrational Integer Functions} and @ref{Irrational Real Functions}
@ftindex srfi-95
@item SRFI-95 @ref{Sorting}
@ftindex srfi-96
@item SRFI-96 @ref{Universal SLIB Procedures}
@end itemize


@node SRFI-1,  , SRFI, SRFI
@subsubsection SRFI-1

@include srfi-1.txi


@node Session Support, System Interface, Standards Support, Other Packages
@section Session Support

@noindent
If @code{(provided? 'abort)}:

@defun abort
Resumes the top level Read-Eval-Print loop.  If provided, @code{abort}
is used by the @code{break} and @code{debug} packages.
@end defun

@menu
* Repl::                        Macros at top-level
* Quick Print::                 Loop-safe Output
* Debug::                       To err is human ...
* Breakpoints::                 Pause execution
* Trace::                       'trace
@end menu

@node Repl, Quick Print, Session Support, Session Support
@subsection Repl

@code{(require 'repl)}
@ftindex repl

Here is a read-eval-print-loop which, given an eval, evaluates forms.

@deffn {Procedure} repl:top-level repl:eval
@code{read}s, @code{repl:eval}s and @code{write}s expressions from
@code{(current-input-port)} to @code{(current-output-port)} until an
end-of-file is encountered.  @code{load}, @code{slib:eval},
@code{slib:error}, and @code{repl:quit} dynamically bound during
@code{repl:top-level}.
@end deffn

@deffn {Procedure} repl:quit
Exits from the invocation of @code{repl:top-level}.
@end deffn

The @code{repl:} procedures establish, as much as is possible to do
portably, a top level environment supporting macros.
@code{repl:top-level} uses @code{dynamic-wind} to catch error conditions
and interrupts.  If your implementation supports this you are all set.

Otherwise, if there is some way your implementation can catch error
conditions and interrupts, then have them call @code{slib:error}.  It
will display its arguments and reenter @code{repl:top-level}.
@code{slib:error} dynamically bound by @code{repl:top-level}.

To have your top level loop always use macros, add any interrupt
catching lines and the following lines to your Scheme init file:
@lisp
(require 'macro)
@ftindex macro
(require 'repl)
@ftindex repl
(repl:top-level macro:eval)
@end lisp


@node Quick Print, Debug, Repl, Session Support
@subsection Quick Print

@code{(require 'qp)}
@ftindex qp

@noindent
When displaying error messages and warnings, it is paramount that the
output generated for circular lists and large data structures be
limited.  This section supplies a procedure to do this.  It could be
much improved.

@quotation
Notice that the neccessity for truncating output eliminates
Common-Lisp's @ref{Format} from consideration; even when variables
@code{*print-level*} and @code{*print-level*} are set, huge strings and
bit-vectors are @emph{not} limited.
@end quotation

@deffn {Procedure} qp arg1 @dots{}
@deffnx {Procedure} qpn arg1 @dots{}
@deffnx {Procedure} qpr arg1 @dots{}
@code{qp} writes its arguments, separated by spaces, to
@code{(current-output-port)}.  @code{qp} compresses printing by
substituting @samp{...} for substructure it does not have sufficient
room to print.  @code{qpn} is like @code{qp} but outputs a newline
before returning.  @code{qpr} is like @code{qpn} except that it returns
its last argument.
@end deffn

@defvar *qp-width*
@var{*qp-width*} is the largest number of characters that @code{qp}
should use.  If @var{*qp-width*} is #f, then all items will be
@code{write}n.  If @var{*qp-width*} is 0, then all items except
procedures will be @code{write}n; procedures will be indicated by
@samp{#[proc]}.
@end defvar


@node Debug, Breakpoints, Quick Print, Session Support
@subsection Debug

@code{(require 'debug)}
@ftindex debug

@noindent
Requiring @code{debug} automatically requires @code{trace} and
@code{break}.

@noindent
An application with its own datatypes may want to substitute its own
printer for @code{qp}.  This example shows how to do this:

@example
(define qpn (lambda args) @dots{})
(provide 'qp)
(require 'debug)
@ftindex debug
@end example

@deffn {Procedure} trace-all file @dots{}
Traces (@pxref{Trace}) all procedures @code{define}d at top-level in
@file{file} @dots{}.
@end deffn

@deffn {Procedure} track-all file @dots{}
Tracks (@pxref{Trace}) all procedures @code{define}d at top-level in
@file{file} @dots{}.
@end deffn

@deffn {Procedure} stack-all file @dots{}
Stacks (@pxref{Trace}) all procedures @code{define}d at top-level in
@file{file} @dots{}.
@end deffn

@deffn {Procedure} break-all file @dots{}
Breakpoints (@pxref{Breakpoints}) all procedures @code{define}d at
top-level in @file{file} @dots{}.
@end deffn


@node Breakpoints, Trace, Debug, Session Support
@subsection Breakpoints

@code{(require 'break)}
@ftindex break

@defun init-debug
If your Scheme implementation does not support @code{break} or
@code{abort}, a message will appear when you @code{(require 'break)} or
@ftindex break
@code{(require 'debug)} telling you to type @code{(init-debug)}.  This
@ftindex debug
is in order to establish a top-level continuation.  Typing
@code{(init-debug)} at top level sets up a continuation for
@code{break}.
@end defun

@defun breakpoint arg1 @dots{}
Returns from the top level continuation and pushes the continuation from
which it was called on a continuation stack.
@end defun

@defun continue
Pops the topmost continuation off of the continuation stack and returns
an unspecified value to it.
@end defun

@defun continue arg1 @dots{}
Pops the topmost continuation off of the continuation stack and returns
@var{arg1} @dots{} to it.
@end defun

@defmac break proc1 @dots{}
Redefines the top-level named procedures given as arguments so that
@code{breakpoint} is called before calling @var{proc1} @dots{}.
@end defmac

@defmac break
With no arguments, makes sure that all the currently broken identifiers
are broken (even if those identifiers have been redefined) and returns a
list of the broken identifiers.
@end defmac

@defmac unbreak proc1 @dots{}
Turns breakpoints off for its arguments.
@end defmac

@defmac unbreak
With no arguments, unbreaks all currently broken identifiers and returns
a list of these formerly broken identifiers.
@end defmac

These are @emph{procedures} for breaking.  If defmacros are not natively
supported by your implementation, these might be more convenient to use.

@defun breakf proc
@defunx breakf proc name
To break, type
@lisp
(set! @var{symbol} (breakf @var{symbol}))
@end lisp
@noindent
or
@lisp
(set! @var{symbol} (breakf @var{symbol} '@var{symbol}))
@end lisp
@noindent
or
@lisp
(define @var{symbol} (breakf @var{function}))
@end lisp
@noindent
or
@lisp
(define @var{symbol} (breakf @var{function} '@var{symbol}))
@end lisp
@end defun

@defun unbreakf proc
To unbreak, type
@lisp
(set! @var{symbol} (unbreakf @var{symbol}))
@end lisp
@end defun


@node Trace,  , Breakpoints, Session Support
@subsection Tracing

@code{(require 'trace)}
@ftindex trace

@noindent
This feature provides three ways to monitor procedure invocations:

@table @asis
@item stack
Pushes the procedure-name when the procedure is called; pops when it
returns.
@item track
Pushes the procedure-name and arguments when the procedure is called;
pops when it returns.
@item trace
Pushes the procedure-name and prints @samp{CALL @var{procedure-name}
@var{arg1} @dots{}} when the procdure is called; pops and prints
@samp{RETN @var{procedure-name} @var{value}} when the procedure returns.
@end table

@defvar debug:max-count
If a traced procedure calls itself or untraced procedures which call it,
stack, track, and trace will limit the number of stack pushes to
@var{debug:max-count}.
@end defvar

@defun print-call-stack
@defunx print-call-stack port
Prints the call-stack to @var{port} or the current-error-port.
@end defun


@defmac trace proc1 @dots{}
Traces the top-level named procedures given as arguments.
@end defmac

@defmac trace
With no arguments, makes sure that all the currently traced identifiers
are traced (even if those identifiers have been redefined) and returns a
list of the traced identifiers.
@end defmac

@defmac track proc1 @dots{}
Traces the top-level named procedures given as arguments.
@end defmac
@defmac track
With no arguments, makes sure that all the currently tracked identifiers
are tracked (even if those identifiers have been redefined) and returns
a list of the tracked identifiers.
@end defmac

@defmac stack proc1 @dots{}
Traces the top-level named procedures given as arguments.
@end defmac
@defmac stack
With no arguments, makes sure that all the currently stacked identifiers
are stacked (even if those identifiers have been redefined) and returns
a list of the stacked identifiers.
@end defmac

@defmac untrace proc1 @dots{}
Turns tracing, tracking, and  off for its arguments.
@end defmac
@defmac untrace
With no arguments, untraces all currently traced identifiers and returns
a list of these formerly traced identifiers.
@end defmac

@defmac untrack proc1 @dots{}
Turns tracing, tracking, and  off for its arguments.
@end defmac
@defmac untrack
With no arguments, untracks all currently tracked identifiers and returns
a list of these formerly tracked identifiers.
@end defmac

@defmac unstack proc1 @dots{}
Turns tracing, stacking, and  off for its arguments.
@end defmac
@defmac unstack
With no arguments, unstacks all currently stacked identifiers and returns
a list of these formerly stacked identifiers.
@end defmac

These are @emph{procedures} for tracing.  If defmacros are not natively
supported by your implementation, these might be more convenient to use.

@defun tracef proc
@defunx tracef proc name
@defunx trackf proc
@defunx trackf proc name
@defunx stackf proc
@defunx stackf proc name
To trace, type
@lisp
(set! @var{symbol} (tracef @var{symbol}))
@end lisp
@noindent
or
@lisp
(set! @var{symbol} (tracef @var{symbol} '@var{symbol}))
@end lisp
@noindent
or
@lisp
(define @var{symbol} (tracef @var{function}))
@end lisp
@noindent
or
@lisp
(define @var{symbol} (tracef @var{function} '@var{symbol}))
@end lisp
@end defun

@defun untracef proc
Removes tracing, tracking, or stacking for @var{proc}.
To untrace, type
@lisp
(set! @var{symbol} (untracef @var{symbol}))
@end lisp
@end defun


@node System Interface, Extra-SLIB Packages, Session Support, Other Packages
@section System Interface

@noindent
If @code{(provided? 'getenv)}:
@ftindex getenv

@defun getenv name
Looks up @var{name}, a string, in the program environment.  If @var{name} is
found a string of its value is returned.  Otherwise, @code{#f} is returned.
@end defun

@noindent
If @code{(provided? 'system)}:
@ftindex system

@defun system command-string
Executes the @var{command-string} on the computer and returns the
integer status code.  This behaves the same as the POSIX @code{system}
call.
@end defun

@noindent
If @code{(provided? 'program-arguments)}:
@ftindex program-arguments

@defun program-arguments
Returns a list of strings, the first of which is the program name
followed by the command-line arguments.
@end defun


@menu
* Directories::                 
* Transactions::                
* CVS::                         
@end menu

@node Directories, Transactions, System Interface, System Interface
@subsection Directories

@include dirs.txi


@node Transactions, CVS, Directories, System Interface
@subsection Transactions

@noindent
If @code{system} is provided by the Scheme implementation, the
@dfn{transact} package provides functions for file-locking and
file-replacement transactions.

@code{(require 'transact)}
@ftindex transact

@include transact.txi


@node CVS,  , Transactions, System Interface
@subsection CVS

@code{(require 'cvs)}
@ftindex cvs

@include cvs.txi


@node Extra-SLIB Packages,  , System Interface, Other Packages
@section Extra-SLIB Packages

Several Scheme packages have been written using SLIB.  There are several
reasons why a package might not be included in the SLIB distribution:
@itemize @bullet
@item
Because it requires special hardware or software which is not universal.
@item
Because it is large and of limited interest to most Scheme users.
@item
Because it has copying terms different enough from the other SLIB
packages that its inclusion would cause confusion.
@item
Because it is an application program, rather than a library module.
@item
Because I have been too busy to integrate it.
@end itemize

Once an optional package is installed (and an entry added to
@code{*catalog*}), the @code{require} mechanism allows it to be called
up and used as easily as any other SLIB package.  Some optional
packages (for which @code{*catalog*} already has entries) available
from SLIB sites are:

@table @asis
@item SLIB-PSD
@cindex PSD
is a portable debugger for Scheme (requires emacs editor).@*
@url{http://groups.csail.mit.edu/mac/ftpdir/scm/slib-psd1-3.tar.gz}@*
@url{ftp://ftp.cs.indiana.edu/pub/scheme-repository/utl/slib-psd1-3.tar.gz}@*

With PSD, you can run a Scheme program in an Emacs buffer, set
breakpoints, single step evaluation and access and modify the
program's variables.  It works by instrumenting the original source
code, so it should run with any R4RS compliant Scheme.  It has been
tested with SCM, Elk 1.5, and the sci interpreter in the Scheme->C
system, but should work with other Schemes with a minimal amount of
porting, if at all.  Includes documentation and user's manual.
@ifset html
Written by Pertti Kellomäki,
@end ifset
@ifclear html
Written by Pertti Kellom@"aki,
@end ifclear
the Lisp Pointers article describing
PSD (Lisp Pointers VI(1):15-23, January-March 1993) is available at@*
@url{http://www.cs.tut.fi/staff/pk/scheme/psd/article/article.html}
@sp 1

@item SCHELOG
@cindex SCHELOG
@cindex Prolog
is an embedding of Prolog in Scheme.@*
@url{http://www.ccs.neu.edu/~dorai/schelog/schelog.html}
@sp 1

@item JFILTER
@cindex JFILTER
@cindex Japanese
@cindex JIS
@cindex EUC
is a Scheme program which converts text among the JIS, EUC, and
Shift-JIS Japanese character sets.@*
@url{http://www.math.u-toyama.ac.jp/~iwao/Scheme/Jfilter}
@end table


@node About SLIB, Index, Other Packages, Top
@chapter About SLIB

@noindent
More people than I can name have contributed to SLIB.  Thanks to all of
you!

@quotation
SLIB @value{SLIBVERSION}, released @value{SLIBDATE}.@*
Aubrey Jaffer <agj@@alum.mit.edu>@*
@c @i{Hyperactive Software} -- The Maniac Inside!@*
@end quotation

Current information about SLIB can be found on SLIB's @dfn{WWW} home
page:

@center @url{http://people.csail.mit.edu/jaffer/SLIB}

SLIB is part of the GNU project.

@menu
* Installation::                How to install SLIB on your system.
* The SLIB script::             Run interactive SLIB sessions.
* Porting::                     SLIB to new platforms.
* Compiled and Implementation-Specific Features::  
* Coding Guidelines::           How to write modules for SLIB.
* Copyrights::                  Intellectual propery issues.
* About this manual::           
@end menu

@node Installation, The SLIB script, About SLIB, About SLIB
@section Installation

@ifset html
<A NAME="Installation"></A>
@end ifset

@cindex install
@cindex installation
There are five parts to installation:

@itemize @bullet
@item
Unpack the SLIB distribution.
@item
Install documentation and @code{slib} script.
@item
Configure the Scheme implementation(s) to locate the SLIB directory
and implementation directories.
@item
Arrange for each Scheme implementation to load its SLIB initialization
file.
@item
Build the SLIB catalog for each Scheme implementation.
@end itemize

@subsection Unpacking the SLIB Distribution

If the SLIB distribution is a GNU/Linux RPM, it will create the SLIB
directory @file{/usr/share/slib}.

If the SLIB distribution is a ZIP file, unzip the distribution to create
the SLIB directory.  Locate this @file{slib} directory either in your
home directory (if only you will use this SLIB installation); or put it
in a location where libraries reside on your system.  On unix systems
this might be @file{/usr/share/slib}, @file{/usr/local/lib/slib}, or
@file{/usr/lib/slib}.  If you know where SLIB should go on other
platforms, please inform agj@@alum.mit.edu.

@subsection Install documentation and slib script

@cindex slib
@cindex script
@example
make infoz
make install
@end example

@subsection Configure Scheme Implementation to Locate SLIB

If the Scheme implementation supports @code{getenv}, then the value of
the shell environment variable @var{SCHEME_LIBRARY_PATH} will be used
for @code{(library-vicinity)} if it is defined.  Currently, Bigloo,
Chez, Elk, Gambit, Gauche, Guile, Jscheme, Larceny, MITScheme,
MzScheme, RScheme, S7, STk, VSCM, and SCM support @code{getenv}.
Scheme48 supports @code{getenv} but does not use it for determining
@code{library-vicinity}.  (That is done from the Makefile.)

The @code{(library-vicinity)} can also be set from the SLIB
initialization file or by implementation-specific means.

@subsection Configure Scheme Implementation to Locate and Implementation Directory

Support for locating an implementation's auxiliary directory is uneven
among implementations.  Also, the person installing SLIB may not have
write permission to some of these directories (necessary for writing
slibcat).  Therefore, those implementations supporting @code{getenv}
(except SCM and Scheme48) provide a means for specifying the
@code{implementation-vicinity} through environment variables.  Define
the indicated environment variable to the pathname (with trailing
slash or backslash) of the desired directory.  Do not use @file{slib/}
as an implementation-vicinity!

@multitable @columnfractions .3 .7
@item Bigloo     @tab BIGLOO_IMPLEMENTATION_PATH
@item Chez       @tab CHEZ_IMPLEMENTATION_PATH
@item ELK        @tab ELK_IMPLEMENTATION_PATH
@item Gambit     @tab GAMBIT_IMPLEMENTATION_PATH
@item Guile      @tab GUILE_IMPLEMENTATION_PATH
@item Jscheme    @tab JSCHEME_IMPLEMENTATION_PATH
@item MIT-Scheme @tab MITSCHEME_IMPLEMENTATION_PATH
@item MzScheme   @tab MZSCHEME_IMPLEMENTATION_PATH
@item RScheme    @tab RSCHEME_IMPLEMENTATION_PATH
@item S7         @tab S7_IMPLEMENTATION_PATH
@item STk        @tab STK_IMPLEMENTATION_PATH
@item Vscm       @tab VSCM_IMPLEMENTATION_PATH
@end multitable

@subsection Loading SLIB Initialization File

If you use the @code{slib} script to start your SLIB session, then
this step is unnecessary.

Check the manifest in @file{README} to find a configuration file for
your Scheme implementation.  Initialization files for most IEEE P1178
compliant Scheme Implementations are included with this distribution.

You should check the definitions of @code{software-type},
@code{scheme-implementation-version},
@iftex
@*
@end iftex
@code{implementation-vicinity},
and @code{library-vicinity} in the initialization file.  There are
comments in the file for how to configure it.

Once this is done, modify the startup file for your Scheme
implementation to @code{load} this initialization file.

@subsection Build New SLIB Catalog for the Implementation

When SLIB is first used from an implementation, a file named
@file{slibcat} is written to the @code{implementation-vicinity} for that
implementation.  Because users may lack permission to write in
@code{implementation-vicinity}, it is good practice to build the new
catalog when installing SLIB.

To build (or rebuild) the catalog, start the Scheme implementation (with
SLIB), then:

@example
(require 'new-catalog)
@end example

The catalog also supports color-name dictionaries.  With an
SLIB-installed scheme implementation, type:
@example
(require 'color-names)
(make-slib-color-name-db)
(require 'new-catalog)
(slib:exit)
@end example

@subsection Implementation-specific Instructions

Multiple implementations of Scheme can all use the same SLIB directory.
Simply configure each implementation's initialization file as outlined
above.


@deftp Implementation SCM
The SCM implementation does not require any initialization file as SLIB
support is already built into SCM.  See the documentation with SCM for
installation instructions.
@end deftp

@deftp Implementation Larceny
Starting with version 0.96, Larceny contains its own SLIB
initialization file, loaded by @code{(require 'srfi-96)}.  If
SCHEME_LIBRARY_PATH is not set, then Larceny looks for an @file{slib}
subdirectory of a directory in the list returned by
@code{(current-require-path)}

@example
larceny -- -e "(require 'srfi-96)"
@end example
@end deftp


@deftp Implementation {Gauche-0.9}
Gauche also supports SLIB.  It finds SLIB at installation time;
@code{(use slib)} to enable.

@example
gosh -u slib
@end example
@end deftp


@deftp Implementation {ELK}
@example
elk -i -l $@{SCHEME_LIBRARY_PATH@}elk.init
@end example
@end deftp


@deftp Implementation {PLT Scheme}
@deftpx Implementation {DrScheme}
@deftpx Implementation {MzScheme}

The @file{init.ss} file in the _slibinit_ collection is an SLIB
initialization file.  To run SLIB in MzScheme:

@example
mzscheme -f $@{SCHEME_LIBRARY_PATH@}mzscheme.init
@end example
@end deftp


@deftp Implementation {MIT Scheme}
@example
scheme -load $@{SCHEME_LIBRARY_PATH@}mitscheme.init
@end example
@end deftp


@deftp Implementation {Gambit-C 3.0}
@example
gsi -:s $@{SCHEME_LIBRARY_PATH@}gambit.init -
@end example
@end deftp


@deftp Implementation SISC
@example
sisc -e "(load \"$@{SCHEME_LIBRARY_PATH@}sisc.init\")" --
@end example
@end deftp


@deftp Implementation Kawa
@example
kawa -f $@{SCHEME_LIBRARY_PATH@}kawa.init --
@end example
@end deftp


@deftp Implementation {Guile}
Guile versions 1.6 and earlier link to an archaic SLIB version.  In
RedHat or Fedora installations:

@example
rm /usr/share/guile/slib
ln -s $@{SCHEME_LIBRARY_PATH@} /usr/share/guile/slib
@end example

In Debian installations:

@example
rm /usr/share/guile/1.6/slib
ln -s $@{SCHEME_LIBRARY_PATH@} /usr/share/guile/1.6/slib
@end example

@code{$@{SCHEME_LIBRARY_PATH@}} is where SLIB gets installed.

Guile before version 1.8 with SLIB can then be started thus:

@example
guile -l $@{SCHEME_LIBRARY_PATH@}guile.init
@end example

Guile version 1.8 and after with SLIB can then be started thus:

@example
guile -l $@{SCHEME_LIBRARY_PATH@}guile.init \
      -l $@{SCHEME_LIBRARY_PATH@}guile.use
@end example

The Guile manual has a different way of installing SLIB:

@exdent @url{http://www.gnu.org/software/guile/manual/html_node/SLIB-installation.html}

@end deftp


@deftp Implementation Scheme48
To make a Scheme48 image for an installation under @code{<prefix>},

@enumerate
@item
@code{cd} to the SLIB directory
@item
type @code{make prefix=<prefix> slib48}.
@item
To install the image, type @code{make prefix=<prefix> install48}.  This
will also create a shell script with the name @code{slib48} which will
invoke the saved image.
@end enumerate
@end deftp

@deftp Implementation VSCM
@format
From: Matthias Blume <blume @@ cs.Princeton.EDU>
Date: Tue, 1 Mar 1994 11:42:31 -0500
@end format

Disclaimer: The code below is only a quick hack.  If I find some time
to spare I might get around to make some more things work.

You have to provide @file{vscm.init} as an explicit command line
argument.  Since this is not very nice I would recommend the following
installation procedure:

@enumerate
@item
run scheme
@item
@code{(load "vscm.init")}
@item
@code{(slib:dump "dumpfile")}
@item
mv dumpfile place-where-vscm-standard-bootfile-resides.  For example:

@code{mv dumpfile /usr/local/vscm/lib/scheme-boot}

In this case vscm should have been compiled with flag:

-DDEFAULT_BOOTFILE='"/usr/local/vscm/lib/scheme-boot"'

See Makefile (definition of DDP) for details.
@end enumerate
@end deftp

@deftp Implementation S7

S7 is not a standalone implementation, but runs as the extension
language for the Snd sound editor.
@file{$@{@var{SCHEME_LIBRARY_PATH}@}s7.init} can be loaded from the
Snd init file or on the Snd command line thus:

@example
snd -l $@{@var{SCHEME_LIBRARY_PATH}@}s7.init
@end example
@end deftp

@node The SLIB script, Porting, Installation, About SLIB
@section The SLIB script

SLIB comes with shell script for Unix platforms.

@example
@b{ slib } [ scheme | scm | gsi | mzscheme | guile
       | scheme48 | scmlit | elk | sisc | kawa ]
@end example

@noindent
Starts an interactive Scheme-with-SLIB session.

@noindent
The optional argument to the @code{slib} script is the Scheme
implementation to run.  Absent the argument, it searches for
implementations in the above order.


@node Porting, Compiled and Implementation-Specific Features, The SLIB script, About SLIB
@section Porting

If there is no initialization file for your Scheme implementation, you
will have to create one.  Your Scheme implementation must be largely
compliant with
@lisp
@cite{IEEE Std 1178-1990},
@cite{Revised^4 Report on the Algorithmic Language Scheme}, or
@cite{Revised^5 Report on the Algorithmic Language Scheme}
@end lisp
@noindent
in order to support SLIB.  @footnote{If you are porting a
@cite{Revised^3 Report on the Algorithmic Language Scheme}
implementation, then you will need to finish writing @file{sc4sc3.scm}
and @code{load} it from your initialization file.}

@noindent
@url{http://cvs.savannah.gnu.org/viewcvs/*checkout*/scm/scm/r4rstest.scm}
is a file which checks compliance with much of R4RS.

@file{Template.scm} is an example configuration file.  The comments
inside will direct you on how to customize it to reflect your system.
Give your new initialization file the implementation's name with
@file{.init} appended.  For instance, if you were porting
@code{foo-scheme} then the initialization file might be called
@file{foo.init}.

Your customized version should then be loaded as part of your scheme
implementation's initialization.  It will load @file{require.scm} from
the library; this will allow the use of @code{provide},
@code{provided?}, and @code{require} along with the @dfn{vicinity}
functions (these functions are documented in the sections
@ref{Feature} and @ref{Require}).  The rest of the library will then
be accessible in a system independent fashion.

Please mail new working configuration files to @code{agj@@alum.mit.edu}
so that they can be included in the SLIB distribution.


@node Compiled and Implementation-Specific Features, Coding Guidelines, Porting, About SLIB
@section Compiled and Implementation-Specific Features

Often an implementation can implement an SLIB feature more efficiently
than the R4RS-compliant source code in SLIB.  Alternatively,
implementations with compilers can compile SLIB source code into
binary files which run faster than loading source code.

Additionally, the SLIB catalog can be augmented with extra-SLIB
features which can be loaded by the implementation.
The catalog format is described in @xref{Library Catalogs}.

These implementation-specific modifications are made when a new
catalog is created (@pxref{Catalog Creation}).  If @file{mkimpcat.scm}
in @code{implementation-invicinity} exists, it is loaded.  That should
produce the file @file{implcat} in @code{implementation-invicinity},
whose associations will override those of SLIB.  @file{implcat} is
copied into @file{slibcat} in @code{implementation-vicinity} as part
of the catalog creation process; modifications to @file{implcat} after
that will have no effect.


@node Coding Guidelines, Copyrights, Compiled and Implementation-Specific Features, About SLIB
@section Coding Guidelines

All library packages are written in IEEE P1178 Scheme and assume that a
configuration file and @file{require.scm} package have already been
loaded.  Other versions of Scheme can be supported in library packages
as well by using, for example, @code{(provided? 'r3rs)} or
@code{(require 'r3rs)} (@pxref{Require}).
@ftindex r3rs

If a procedure defined in a module is called by other procedures in
that module, then those procedures should instead call an alias
defined in that module:

@lisp
(define module-name:foo foo)
@end lisp

The module name and @samp{:} should prefix that symbol for the
internal name.  Do not export internal aliases.

A procedure is exported from a module by putting Schmooz-style
comments (@pxref{Schmooz}) or @samp{;@@} at the beginning of the line
immediately preceding the definition (@code{define},
@code{define-syntax}, or @code{defmacro}).  Modules, exports and other
relevant issues are discussed in @ref{Compiling Scheme}.

Code submitted for inclusion in SLIB should not duplicate (more than
one) routines already in SLIB files.  Use @code{require} to force
those library routines to be used by your package.

Documentation should be provided in Emacs Texinfo format if possible,
but documentation must be provided.

Your package will be released sooner with SLIB if you send me a file
which tests your code.  Please run this test @emph{before} you send me
the code!

@subsection Modifications

Please document your changes.  A line or two for @file{ChangeLog} is
sufficient for simple fixes or extensions.  Look at the format of
@file{ChangeLog} to see what information is desired.  Please send me
@code{diff} files from the latest SLIB distribution (remember to send
@code{diff}s of @file{slib.texi} and @file{ChangeLog}).  This makes for
less email traffic and makes it easier for me to integrate when more
than one person is changing a file (this happens a lot with
@file{slib.texi} and @samp{*.init} files).

If someone else wrote a package you want to significantly modify, please
try to contact the author, who may be working on a new version.  This
will insure against wasting effort on obsolete versions.

Please @emph{do not} reformat the source code with your favorite
beautifier, make 10 fixes, and send me the resulting source code.  I do
not have the time to fish through 10000 diffs to find your 10 real fixes.


@node Copyrights, About this manual, Coding Guidelines, About SLIB
@section Copyrights

@ifset html
<A NAME="Copyrights"></A>
@end ifset

This section has instructions for SLIB authors regarding copyrights.
@cindex copyright

Each package in SLIB must either be in the public domain, or come with a
statement of terms permitting users to copy, redistribute and modify it.
The comments at the beginning of @file{require.scm} and
@file{macwork.scm} illustrate copyright and appropriate terms.

If your code or changes amount to less than about 10 lines, you do not
need to add your copyright or send a disclaimer.

@subsection Putting code into the Public Domain

In order to put code in the public domain you should sign a copyright
disclaimer and send it to the SLIB maintainer.  Contact
agj@@alum.mit.edu for the address to mail the disclaimer to.

@need 1000
@quotation
I, @var{<my-name>}, hereby affirm that I have placed the software
package @var{<name>} in the public domain.

I affirm that I am the sole author and sole copyright holder for the
software package, that I have the right to place this software package
in the public domain, and that I will do nothing to undermine this
status in the future.
@flushright
                                        @var{signature and date}
@end flushright
@end quotation

This wording assumes that you are the sole author.  If you are not the
sole author, the wording needs to be different.  If you don't want to
be bothered with sending a letter every time you release or modify a
module, make your letter say that it also applies to your future
revisions of that module.

Make sure no employer has any claim to the copyright on the work you
are submitting.  If there is any doubt, create a copyright disclaimer
and have your employer sign it.  Mail the signed disclaimer to the
SLIB maintainer.  Contact agj@@alum.mit.edu for the address to mail
the disclaimer to.  An example disclaimer follows.

@subsection Explicit copying terms

@noindent
If you submit more than about 10 lines of code which you are not
placing into the Public Domain (by sending me a disclaimer) you need
to:

@itemize @bullet
@item
Arrange that your name appears in a copyright line for the appropriate
year.  Multiple copyright lines are acceptable.
@item
With your copyright line, specify any terms you require to be
different from those already in the file.
@item
Make sure no employer has any claim to the copyright on the work you
are submitting.  If there is any doubt, create a copyright disclaimer
and have your employer sign it.  Mail the signed disclaim to the SLIB
maintainer.  Contact agj@@alum.mit.edu for the address to mail the
disclaimer to.
@end itemize

@subsection Example: Company Copyright Disclaimer

This disclaimer should be signed by a vice president or general
manager of the company.  If you can't get at them, anyone else
authorized to license out software produced there will do.  Here is a
sample wording:

@quotation
@var{<employer>} Corporation hereby disclaims all copyright
interest in the program @var{<program>} written by @var{<name>}.

@var{<employer>} Corporation affirms that it has no other intellectual
property interest that would undermine this release, and will do
nothing to undermine it in the future.

@flushleft
@var{<signature and date>},
@var{<name>}, @var{<title>}, @var{<employer>} Corporation
@end flushleft
@end quotation


@node About this manual,  , Copyrights, About SLIB
@section About this manual

@itemize @bullet
@item
Entries that are labeled as Functions are called for their return
values.  Entries that are labeled as Procedures are called primarily for
their side effects.

@item
Examples in this text were produced using the @code{scm} Scheme
implementation.

@item
At the beginning of each section, there is a line that looks like:
@ftindex feature
@example
(require 'feature)
@end example
Include this line in your code prior to using the package.
@end itemize

@menu
* GNU Free Documentation License::  
@end menu

@node GNU Free Documentation License,  , About this manual, About this manual
@subsection GNU Free Documentation License

@include fdl.texi

@ifinfo
@node Index,  , About SLIB, Top
@unnumbered Index
@end ifinfo

@include indexes.texi
@bye
