# S

`*Scl`
  A global variable holding the current fixpoint input scale. See also Numbers and `scl`.

      : (str "123.45")  # Default value of '*Scl' is 0
      -> (123)
      : (setq *Scl 3)
      -> 3
      : (str "123.45")
      -> (123450)

      : 123.4567
      -> 123457
      : 12.3456
      -> 12346

`*Sig1`
`*Sig2`
  Global variables holding (possibly empty) `prg` bodies, which will be executed when a SIGUSR1 signal (or a SIGUSR2 signal, respectively) is sent to the current process. See also `alarm`, `*Hup`, `sigio`, `*TStp[12]` and `*Winch`.

      : (de *Sig1 (msg 'SIGUSR1))
      -> *Sig1

`*Solo`
  A global variable indicating exclusive database access. Its value is `0` initially, set to `T` (or `NIL`) during cooperative database locks when `lock` is successfully called with a `NIL` (or non-`NIL`) argument. See also `*Zap`.

      : *Solo
      -> 0
      : (lock *DB)
      -> NIL
      : *Solo
      -> NIL
      : (rollback)
      -> T
      : *Solo
      -> 0
      : (lock)
      -> NIL
      : *Solo
      -> T
      : (rollback)
      -> T
      : *Solo
      -> T

`+Sn`
  Prefix class for maintaining indexes according to a modified soundex algorithm, for tolerant name searches, to `+String` relations. Typically used in combination with the `+Idx` prefix class. See also Database.

      (rel nm (+Sn +Idx +String))  # Name

`+String`
  Class for string (transient symbol) relations, a subclass of `+Symbol`. Accepts an optional argument for the string length (currently not used). See also Database.

      (rel nm (+Sn +Idx +String))  # Name, indexed by soundex and substrings

`+Swap`
  Prefix class for `+relation`s where the data are to be stored in the value of a separate external symbol instead of the relation's object. Typically used for data which are relatively large and/or rarely accessed. Doesn't work with bidirectional relations (`+Joint` or `+index`). See also Database.

      (rel pw (+Swap +String))               # Password
      (rel nr (+Swap +List +Number))         # List of bignums

`+Symbol`
  Class for symbolic relations, a subclass of `+relation`. Objects of that class typically maintain internal symbols, as opposed to the more often-used `+String` for transient symbols. See also Database.

      (rel perm (+List +Symbol))  # Permission list

`same/3`
  Pilog predicate that succeeds if the first argument matches the result of applying the `get` algorithm to the following arguments. Typically used as filter predicate in `select/3` database queries. See also `isa/2`, `bool/3`, `range/3`, `head/3`, `fold/3`, `part/3` and `tolr/3`.

      : (?
         @Nr 2
         @Nm "Spare"
         (select (@Item)
            ((nr +Item @Nr) (nm +Item @Nm))
            (same @Nr @Item nr)
            (head @Nm @Item nm) ) )
       @Nr=2 @Nm="Spare" @Item={B2}

`(scan 'tree ['fun] ['any1] ['any2] ['flg])`
  Scans through a database tree by applying `fun` to all key-value pairs. `fun` should be a function accepting two arguments for key and value. It defaults to `println`. `any1` and `any2` may specify a range of keys. If `any2` is greater than `any1`, the traversal will be in opposite direction. Note that the keys need not to be atomic, depending on the application's index structure. If `flg` is non-`NIL`, partial keys are skipped. See also `tree`, `iter`, `init` and `step`.

      : (scan (tree 'nm '+Item))
      ("ASLRSNSTRSTN" {B3} . T) {B3}
      ("Additive" {B4}) {B4}
      ("Appliance" {B6}) {B6}
      ("Auxiliary Construction" . {B3}) {B3}
      ("Construction" {B3}) {B3}
      ("ENNSNNTTTF" {B4} . T) {B4}
      ("Enhancement Additive" . {B4}) {B4}
      ("Fittings" {B5}) {B5}
      ("GTSTFLNS" {B6} . T) {B6}
      ("Gadget Appliance" . {B6}) {B6}
      ...

      : (scan (tree 'nm '+Item) println NIL T T)  # 'flg' is non-NIL
      ("Auxiliary Construction" . {B3}) {B3}
      ("Enhancement Additive" . {B4}) {B4}
      ("Gadget Appliance" . {B6}) {B6}
      ("Main Part" . {B1}) {B1}
      ("Metal Fittings" . {B5}) {B5}
      ("Spare Part" . {B2}) {B2}
      -> NIL

`(scl 'num [. prg]) -> num`
  If `prg` is given, it binds `*Scl` dynamically to `num` during the execution of `prg`. Otherwise, it sets `*Scl` globally to `num`. See also Numbers.

      : (scl 0)
      -> 0
      : (str "123.45")
      -> (123)
      : (scl 1)
      -> 1
      : (read)
      123.45
      -> 1235
      : (scl 3)
      -> 3
      : (str "123.45")
      -> (123450)
      : (scl 1 (str "123.45"))
      -> (1235)
      : *Scl
      -> 3

`(script 'any ..) -> any`
  The first `any` argument is `load`ed, with the remaining arguments `pass`ed as variable arguments. They can be accessed with `next`, `arg`, `args` and `rest`. With that, the syntax in the script is the same as that in the body of a function with variable arguments (see lambda expressions, "when the CAR is the symbol @").

      $ cat x
      (* (next) (next))

      $ pil +
      : (script "x" 3 4)
      -> 12

`(sect 'lst 'lst) -> lst`
  Returns the intersection of the `lst` arguments. See also `diff`.

      : (sect (1 2 3 4) (3 4 5 6))
      -> (3 4)
      : (sect (1 2 3) (4 5 6))
      -> NIL

`(seed 'any) -> cnt`
  Initializes the random generator's seed, and returns a pseudo random number in the range -2147483648 .. +2147483647. See also `rand` and `hash`.

      : (seed "init string")
      -> -417605464
      : (rand)
      -> -1061886707
      : (rand)
      -> 822065436

      : (seed (time))
      -> 128285383

`(seek 'fun 'lst ..) -> lst`
  Applies `fun` to `lst` and all successive CDRs, until non-`NIL` is returned. Returns the tail of `lst` starting with that element (and stores the non-`NIL` value in the global variable `@@`), or `NIL` if `fun` did not return non-`NIL` for any element of `lst`. When additional `lst` arguments are given, they are passed to `fun` in the same way. See also `find`, `pick`.

      : (seek '((X) (> (car X) 9)) (1 5 8 12 19 22))
      -> (12 19 22)

`(select [var ..] cls [hook|T] [var val ..]) -> obj | NIL`
  (Debug mode only) Interactive database function, loosely modelled after the SQL '`SELECT`' command. A (limited) front-end to the Pilog `select/3` predicate. When called with only a `cls` argument, `select` steps through all objects of that class, and `show`s their complete contents (this is analog to 'SELECT * from CLS'). If `cls` is followed by attribute/value specifications, the search is limited to these values (this is analog to 'SELECT * from CLS where VAR = VAL'). If between the `select` function and `cls` one or several attribute names are supplied, only these attribute (instead of the full `show`) are printed. These attribute specifications may also be lists, then the `get` algorithm will be used to retrieve related data. See also Database and Pilog.

      : (select +Item)                       # Show all items
      {B1} (+Item)
         nr 1
         pr 29900
         inv 100
         sup {C1}
         nm "Main Part"

      {B2} (+Item)
         nr 2
         pr 1250
         inv 100
         sup {C2}
         nm "Spare Part"
      .                                      # Stop
      -> {B2}

      : (select +Item nr 3)                  # Show only item 3
      {B3} (+Item)
         nr 3
         sup {C1}
         pr 15700
         nm "Auxiliary Construction"
         inv 100
      .                                      # Stop
      -> {B3}

      # Show selected attributes for items 3 through 3
      : (select nr nm pr (sup nm) +Item nr (3 . 5))
      3 "Auxiliary Construction" 157.00 "Active Parts Inc." {B3}
      4 "Enhancement Additive" 9.99 "Seven Oaks Ltd." {B4}
      5 "Metal Fittings" 79.80 "Active Parts Inc." {B5}
      -> NIL

`select/3`
  Pilog database predicate that allows combined searches over `+index` and other relations. It takes a list of Pilog variables, a list of generator clauses, and an arbitrary number of filter clauses. The functionality is described in detail in The 'select' Predicate. See also `db/3`, `isa/2`, `same/3`, `bool/3`, `range/3`, `head/3`, `fold/3`, `part/3`, `tolr/3` and `remote/2`.

      : (?
         @Nr (2 . 5)          # Select all items with numbers between 2 and 5
         @Sup "Active"        # and suppliers matching "Active"
         (select (@Item)                                  # Bind results to '@Item'
            ((nr +Item @Nr) (nm +CuSu @Sup (sup +Item)))  # Generator clauses
            (range @Nr @Item nr)                          # Filter clauses
            (part @Sup @Item sup nm) ) )
       @Nr=(2 . 5) @Sup="Active" @Item={B3}
       @Nr=(2 . 5) @Sup="Active" @Item={B5}
      -> NIL

`(send 'msg 'obj ['any ..]) -> any`
  Sends the message `msg` to the object `obj`, optionally with arguments `any`. If the message cannot be located in `obj`, its classes and superclasses, an error `"Bad message"` is issued. See also OO Concepts, `try`, `method`, `meth`, `super` and `extra`.

      : (send 'stop> Dlg)  # Equivalent to (stop> Dlg)
      -> NIL

`(seq 'cnt|sym1) -> sym | NIL`
  Sequential single step: Returns the first external symbol in the `cnt`'th database file, or the next external symbol following `sym1` in the database, or `NIL` when the end of the database is reached. See also `free`.

      : (pool "db")
      -> T
      : (seq *DB)
      -> {2}
      : (seq @)
      -> {3}

`(set 'var 'any ..) -> any`
  Stores new values `any` in the `var` arguments. See also `setq`, `val`, `swap`, `con` and `def`.

      : (set 'L '(a b c)  (cdr L) 999)
      -> 999
      : L
      -> (a 999 c)

`(set! 'obj 'any) -> any`
  Transaction wrapper function for `set`. Note that for setting the value of entities typically the `set!>` message is used. See also `new!`, `request!`, `put!` and `inc!`.

      (set! Obj (* Count Size))  # Setting a non-entity object to a numeric value

`(setq var 'any ..) -> any`
  Stores new values `any` in the `var` arguments. See also `set`, `val` and `def`.

      : (setq  A 123  B (list A A))  # Set 'A' to 123, then 'B' to (123 123)
      -> (123 123)

`(show 'any ['sym|cnt ..]) -> any`
  Shows the name, value and property list of a symbol found by applying the `get` algorithm to `any` and the following arguments. See also `view`.

      : (setq A 123456)
      -> 123456
      : (put 'A 'x 1)
      -> 1
      : (put 'A 'lst (9 8 7))
      -> (9 8 7)
      : (put 'A 'flg T)
      -> T

      : (show 'A)
      A 123456
         flg
         lst (9 8 7)
         x 1
      -> A

      : (show 'A 'lst 2)
      -> 8

`show/1`
  Pilog predicate that always succeeds, and shows the name, value and property list of the argument symbol. See also `show`.

      : (? (db nr +Item 2 @Item) (show @Item))
      {B2} (+Item)
         nm "Spare Part"
         nr 2
         pr 1250
         inv 100
         sup {C2}
       @Item={B2}
      -> NIL

`(sigio 'cnt . prg) -> cnt`
  Sets a signal handler `prg` for SIGIO on the file descriptor `cnt`. Returns the file descriptor. See also `alarm`, `*Hup`, `*Sig[12]`, `*TStp[12]` and `*Winch`.

      # First session
      : (sigio (setq *SigSock (port T 4444))  # Register signal handler at UDP port
         (while (udp *SigSock)                # Queue all received data
            (fifo '*SigQueue @) ) )
      -> 3

      # Second session
      : (for I 7 (udp "localhost" 4444 I))  # Send numbers to first session

      # First session
      : (fifo '*SigQueue)
      -> 1
      : (fifo '*SigQueue)
      -> 2

`(size 'any) -> cnt`
  Returns the "size" of `any`. For numbers this is the number of bytes needed for the value, for external symbols it is the number of bytes it would occupy in the database, for other symbols it is the number of bytes occupied by the UTF-8 representation of the name, and for lists it is the total number of cells in this list and all its sublists. See also `length` and `bytes`.

      : (size "abc")
      -> 3
      : (size "äbc")
      -> 4
      : (size 127)  # One byte
      -> 1
      : (size 128)  # Two bytes (eight bits plus sign bit!)
      -> 2
      : (size (1 (2) 3))
      -> 4
      : (size (1 2 3 .))
      -> 3

`(skip ['any]) -> sym`
  Skips all whitespace (and comments if `any` is given) in the input stream. Returns the next available character, or `NIL` upon end of file. See also `peek` and `eof`.

      $ cat a
      # Comment
      abcd
      $ pil +
      : (in "a" (skip "#"))
      -> "a"

`(solve 'lst [. prg]) -> lst`
  Evaluates a Pilog query and, returns the list of result sets. If `prg` is given, it is executed for each result set, with all Pilog variables bound to their matching values, and returns a list of the results. See also `pilog`, `?`, `goal` and `prove`.

      : (solve '((append @X @Y (a b c))))
      -> (((@X) (@Y a b c)) ((@X a) (@Y b c)) ((@X a b) (@Y c)) ((@X a b c) (@Y)))

      : (solve '((append @X @Y (a b c))) @X)
      -> (NIL (a) (a b) (a b c))

`(sort 'lst ['fun]) -> lst`
  Returns a sorted list by destructively exchanging the elements of `lst`. If `fun` is given, it is used as a "less than" predicate for comparisons. Typically, `sort` is used in combination with by, giving shorter and often more efficient solutions than with the predicate function. See also Comparing, `group`, `maxi`, `mini` and `uniq`.

      : (sort '(a 3 1 (1 2 3) d b 4 T NIL (a b c) (x y z) c 2))
      -> (NIL 1 2 3 4 a b c d (1 2 3) (a b c) (x y z) T)
      : (sort '(a 3 1 (1 2 3) d b 4 T NIL (a b c) (x y z) c 2) >)
      -> (T (x y z) (a b c) (1 2 3) d c b a 4 3 2 1 NIL)
      : (by cadr sort '((1 4 3) (5 1 3) (1 2 4) (3 8 5) (6 4 5)))
      -> ((5 1 3) (1 2 4) (1 4 3) (6 4 5) (3 8 5))

`(space ['cnt]) -> cnt`
  Prints `cnt` spaces, or a single space when `cnt` is not given. See also `beep`, `prin` and `char`.

      : (space)
       -> 1
      : (space 1)
       -> 1
      : (space 2)
        -> 2

`(sp? 'any) -> flg`
  Returns `T` when the argument `any` is `NIL`, or if it is a string (symbol) that consists only of whitespace characters.

      : (sp? "  ")
      -> T
      : (sp? "ABC")
      -> NIL
      : (sp? 123)
      -> NIL

`(split 'lst 'any ..) -> lst`
  Splits `lst` at all places containing an element `any` and returns the resulting list of sublists. See also `stem`.

      : (split (1 a 2 b 3 c 4 d 5 e 6) 'e 3 'a)
      -> ((1) (2 b) (c 4 d 5) (6))
      : (mapcar pack (split (chop "The quick brown fox") " "))
      -> ("The" "quick" "brown" "fox")

`(sqrt 'num ['flg|num]) -> num`
  Returns the square root of the `num` argument. If `flg` is given and non-`NIL`, the result will be rounded. If in addition to that `flg` is a number, the first argument will be multiplied with it before doing the square root calculation. See also `*/`.

      : (sqrt 64)
      -> 8
      : (sqrt 1000)
      -> 31
      : (sqrt 1000 T)
      -> 32
      : (sqrt 10000000000000000000000000000000000000000)
      -> 100000000000000000000

      : (scl 6)
      -> 6
      : (sqrt 2.0 1.0)
      -> 1414214

`(ssl 'host 'path . prg) -> any`
  Executes `prg` in an input stream (using `in`) from "@bin/ssl" requesting `path` from `host`.

      : (ssl "picolisp.com" "wiki/?home" (line T))
      -> "<!DOCTYPE html>"

`(stack ['cnt]) -> cnt | (.. sym . cnt)`
  Maintains the stack segment size for coroutines (the main stack segment is limited - while at least one coroutine is running - to four times that size). If called without a `cnt` argument, or if already one or more coroutines are running, the current size in kilobytes is returned. Otherwise, the stack segment size is set to the new value (default 64 kB). If there are running coroutines, their tags will be `cons`ed in front of the size. See also `heap`.

      $ ulimit -s unlimited  &&  pil +  # Guarantee stack space
      : (stack)      # Current size
      -> 64          # 64 kB
      : (stack 200)  # Set to 200 kB
      -> 200
      : (co 'inc (let N 0 (loop (yield (inc 'N)))))  # Create two coroutines
      -> 1
      : (co 'dec (let N 0 (loop (yield (dec 'N)))))
      -> -1
      : (stack)
      -> (dec inc . 200)

`(stamp ['dat 'tim]|['T]) -> sym`
  Returns a date-time string in the form "YYYY-MM-DD HH:MM:SS". If `dat` and `tim` is missing, the current date and time is used. If `T` is passed, the current Coordinated Universal Time (UTC) is used instead. See also `date` and `time`.

      : (stamp)
      -> "2000-09-12 07:48:04"
      : (stamp (date) 0)
      -> "2000-09-12 00:00:00"
      : (stamp (date 2000 1 1) (time 12 0 0))
      -> "2000-01-01 12:00:00"

`(state 'var (sym|lst exe [. prg]) ..) -> any`
  Implements a finite state machine. The variable `var` holds the current state as a symbolic value. When a clause is found that contains the current state in its CAR `sym|lst` value, and where the `exe` in its CADR evaluates to non-`NIL`, the current state will be set to that value, the body `prg` in the CDDR will be executed, and the result returned. `T` is a catch-all for any state. If no state-condition matches, `NIL` is returned. See also `case`, `cond` and `job`.

      : (de tst ()
         (job '((Cnt . 4))
            (state '(start)
               (start 'run
                  (printsp 'start) )
               (run (and (gt0 (dec 'Cnt)) 'run)
                  (printsp 'run) )
               (run 'stop
                  (printsp 'run) )
               (stop 'start
                  (setq Cnt 4)
                  (println 'stop) ) ) ) )
      -> tst
      : (do 12 (tst))
      start run run run run stop
      start run run run run stop
      -> stop
      : (pp 'tst)
      (de tst NIL
         (job '((Cnt . 4))
            (state '(start)
            ...
      -> tst
      : (do 3 (tst))
      start run run -> run
      : (pp 'tst)
      (de tst NIL
         (job '((Cnt . 2))
            (state '(run)
            ...
      -> tst

`(stem 'lst 'any ..) -> lst`
  Returns the tail of `lst` that does not contain any of the `any` arguments. `(stem 'lst 'any ..)` is equivalent to `(last (split 'lst 'any ..))`. See also `tail` and `split`.

      : (stem (chop "abc/def\\ghi") "/" "\\")
      -> ("g" "h" "i")

`(step 'lst ['flg]) -> any`
  Single-steps iteratively through a database tree. `lst` is a structure as received from `init`. If `flg` is non-`NIL`, partial keys are skipped. The key for each returned value is stored in the global variable `@@`. See also `tree`, `scan`, `iter`, `leaf` and `fetch`.

      : (setq Q (init (tree 'nr '+Item) 3 5))
      -> (((3 . 5) ((3 NIL . {B3}) (4 NIL . {B4}) (5 NIL . {B5}) (6 NIL . {B6}))))
      : (get (step Q) 'nr)
      -> 3
      : (get (step Q) 'nr)
      -> 4
      : (get (step Q) 'nr)
      -> 5
      : (get (step Q) 'nr)
      -> NIL

`(store 'tree 'any1 'any2 ['(num1 . num2)])`
  Stores a value `any2` for the key `any1` in a database tree. `num1` is a database file number, as used in `new` (defaulting to 1), and `num2` a database block size (defaulting to 256). When `any2` is `NIL`, the corresponding entry is deleted from the tree. See also `tree` and `fetch`.

      : (store (tree 'nr '+Item) 2 '{B2})

`(str 'sym ['sym1]) -> lst`
`(str 'lst) -> sym`
  In the first form, the string `sym` is parsed into a list. This mechanism is also used by `load`. If `sym1` is given, it should specify a set of characters, and `str` will then return a list of tokens analog to `read`. The second form does the reverse operation by building a string from a list. See also `any`, `name` and `sym`.

      : (str "a (1 2) b")
      -> (a (1 2) b)
      : (str '(a "Hello" DEF))
      -> "a \"Hello\" DEF"
      : (str "a*3+b*4" "_")
      -> (a "*" 3 "+" b "*" 4)

`(str? 'any) -> sym | NIL`
  Returns the argument `any` when it is a transient symbol (string), otherwise `NIL`. See also `sym?`, `box?` and `ext?`.

      : (str? 123)
      -> NIL
      : (str? '{ABC})
      -> NIL
      : (str? 'abc)
      -> NIL
      : (str? "abc")
      -> "abc"

`(strDat 'sym) -> dat`
  Converts a string `sym` in the date format of the current `locale` to a `date`. See also `expDat`, `$dat` and `datStr`.

      : (strDat "2007-06-01")
      -> 733134
      : (strDat "01.06.2007")
      -> NIL
      : (locale "DE" "de")
      -> NIL
      : (strDat "01.06.2007")
      -> 733134
      : (strDat "1.6.2007")
      -> 733134

`(strip 'any) -> any`
  Strips all leading `quote` calls from `any`. See also `lit`.

      : (strip 123)
      -> 123
      : (strip '''(a))
      -> (a)
      : (strip (quote quote a b c))
      -> (a b c)

`(struct 'num 'any 'any ..) -> any`
  Creates or extracts data structures, suitable to be passed to or returned from `native` C functions. The first `num` argument should be a native value, either a scalar, or a pointer obtained by calling functions like `malloc()`. The second argument `any` is a result specification, while all following initialization items are stored in the structure pointed to by the first argument. See also Native C Calls.

      : (scl 2)
      -> 2

      ## /* We assume the following C structure */
      ## typedef struct value {
      ##    int x, y;
      ##    double a, b, c;
      ##    long z;
      ##    char nm[4];
      ## } value;

      # Allocate structure
      : (setq P (native "@" "malloc" 'N 56))
      -> 9204032

      # Store two integers, three doubles, one long, and four characters
      : (struct P 'N -7 -4 (1.0 0.11 0.22 0.33) (7 . 8) 65 66 67 0)
      -> 9204032

      # Extract the structure
      : (struct P '((I . 2) (1.0 . 3) N (C . 4)))
      -> ((7 4) (11 22 33) 7 ("A" "B" "C"))

      # Do both in a single call (allowing conversions of data types)
      : (struct P
         '((I . 2) (1.0 . 3) N (C . 4))
         -7 -4 (1.0 0.11 0.22 0.33) (7 . 8) 65 66 67 0 )
      -> ((7 4) (11 22 33) 7 ("A" "B" "C"))

      # De-allocate structure
      : (native "@" "free" NIL P)
      -> NIL

`(sub? 'any1 'any2) -> any2 | NIL`
  Returns `any2` when the string representation of `any1` is a substring of the string representation of `any2`. See also `pre?`, `offset` and `index`.

      : (sub? "def" "abcdefg")
      -> "abcdefg"
      : (sub? "abb" "abcdefg")
      -> NIL
      : (sub? NIL "abcdefg")
      -> "abcdefg"

      : (sub? "def" '(a b c d e f g))
      -> "abcdefg"
      : (sub? '(d e f) "abcdefg")
      -> "abcdefg"

`(subr 'sym) -> num`
  Converts a Lisp-function that was previously converted with `expr` back to a SUBR function.

      : car
      -> 67313448
      : (expr 'car)
      -> (@ (pass $385260187))
      : (subr 'car)
      -> 67313448
      : car
      -> 67313448

`(sum 'fun 'lst ..) -> num`
  Applies `fun` to each element of `lst`. When additional `lst` arguments are given, their elements are also passed to `fun`. Returns the sum of all numeric values returned from `fun`.

      : (setq A 1  B 2  C 3)
      -> 3
      : (sum val '(A B C))
      -> 6
      : (sum * (3 4 5) (5 6 7))        # Vector dot product
      -> 74
      : (sum                           # Total size of symbol list values
         '((X)
            (and (pair (val X)) (size @)) )
         (what) )
      -> 32021

`(super ['any ..]) -> any`
  Can only be used inside methods. Sends the current message to the current object `This`, this time starting the search for a method at the superclass(es) of the class where the current method was found. See also OO Concepts, `extra`, `method`, `meth`, `send` and `try`.

      (dm stop> ()         # 'stop>' method of current class
         (super)           # Call the 'stop>' method of the superclass
         ... )             # other things

`(swap 'var 'any) -> any`
  Set the value of `var` to `any`, and return the previous value. See also `xchg` and `set`.

      : (setq A 7  L (1 2 3))
      -> (1 2 3)
      : (swap (cdr L) (swap 'A 'xyz))
      -> 2
      : A
      -> xyz
      : L
      -> (1 7 3)

`(sym 'any) -> sym`
  Generate the printed representation of `any` into the name of a new symbol `sym`. This is the reverse operation of `any`. See also `name` and `str`.

      : (sym '(abc "Hello" 123))
      -> "(abc \"Hello\" 123)"

`(sym? 'any) -> flg`
  Returns `T` when the argument `any` is a symbol. See also `num?`, `atom`, `pair`, `str?`, `box?` and `ext?`.

      : (sym? 'a)
      -> T
      : (sym? NIL)
      -> T
      : (sym? 123)
      -> NIL
      : (sym? '(a b))
      -> NIL

`(symbols) -> lst`
`(symbols 'lst) -> lst`
`(symbols 'lst . prg) -> any`
`(symbols 'sym1 'sym2 ..) -> lst`
  Creates and manages namespaces of internal symbols: In the first form, the current list of namespaces is returned. In the second form, the current namespace list is set to `lst`, and the previous namespace list is returned. In the third form, the current namespace list is set to `lst` during the execution of `prg`, and the result is returned. In the fourth form, `sym1` is initialized to a new namespace if its value is `NIL` and not modified otherwise, and `sym1`, `sym2` and all following arguments are set as the current namespace list. See also `pico`, `nsp`, `-symbols`, `private`, `local`, `export`, `import`, `intern` and `load`.

      : (symbols 'myLib 'pico)
      -> (pico)
      myLib: (de foo (X)
         (bar (inc X)) )
      -> foo
      myLib: (symbols 'pico)
      -> (myLib pico)
      : (pp 'foo)
      (de foo . NIL)
      -> foo
      : (pp 'myLib~foo)
      (de "foo" (X)
         ("bar" (inc X)) )
      -> "foo"
      : (symbols '(myLib pico))
      -> (pico)
      myLib: (pp 'foo)
      (de foo (X)
         (bar (inc X)) )
      -> foo
      myLib:

`(-symbols) -> lst`
  Command line frontend to `symbols`. Inserts the next command line argument as the first namespace into the current search order. `--symbols myLib` on the command line (see Invocation) is equivalent to `-"symbols '(myLib ...)"`. See also `opt`.

      $ ./pil lib/gis.l lib/simul.l  --symbols gis  --symbols simul  +
      simul: (symbols)
      -> (simul gis pico)
      simul:

`(sync) -> flg`
  Waits for pending data from all family processes. While other processes are still sending data (via the `tell` mechanism), a `select` system call is executed for all file descriptors and timers in the `VAL` of the global variable `*Run`. When used in a non-database context, `(tell)` should be called in the end to inform the parent process that it may grant synchronization to other processes waiting for `sync`. In a database context, where `sync` is usually called by `dbSync`, this is not necessary because it is done internally by `commit` or `rollback`. See also `key` and `wait`.

      : (or (lock) (sync))       # Ensure database consistency
      -> T                       # (numeric process-id if lock failed)

`(sys 'any ['any]) -> sym`
  Returns or sets a system environment variable.

      : (sys "TERM")  # Get current value
      -> "xterm"
      : (sys "TERM" "vt100")  # Set new value
      -> "vt100"
      : (sys "TERM")
      -> "vt100"

`(sysdefs 'sym1 '[sym2])`
  Loads system-dependent definitions for all symbols in the section named `sym1` from the file "@lib/sysdefs" (or an alternative file given by `sym2`). All symbols in that section are `def`ined to their given values. See also `native`.

      : (sysdefs "networking")  # Load networking system definitions