Introduction¶

Three new features were introduced into clang at the same time: NSNumber Literals provide a syntax for creating NSNumber from scalar literal expressions; Collection Literals provide a short-hand for creating arrays and dictionaries; Object Subscripting provides a way to use subscripting with Objective-C objects. Users of Apple compiler releases can use these features starting with the Apple LLVM Compiler 4.0. Users of open-source LLVM.org compiler releases can use these features starting with clang v3.1.

These language additions simplify common Objective-C programming patterns, make programs more concise, and improve the safety of container creation.

This document describes how the features are implemented in clang, and how to use them in your own programs.

NSNumber Literals¶

The framework class NSNumber is used to wrap scalar values inside objects: signed and unsigned integers (char, short, int, long, long long), floating point numbers (float, double), and boolean values (BOOL, C++ bool). Scalar values wrapped in objects are also known as boxed values.

In Objective-C, any character, numeric or boolean literal prefixed with the '@' character will evaluate to a pointer to an NSNumber object initialized with that value. C’s type suffixes may be used to control the size of numeric literals.

void main(int argc, const char *argv[]) {
  // character literals.
  NSNumber *theLetterZ = @'Z';          // equivalent to [NSNumber numberWithChar:'Z']

  // integral literals.
  NSNumber *fortyTwo = @42;             // equivalent to [NSNumber numberWithInt:42]
  NSNumber *fortyTwoUnsigned = @42U;    // equivalent to [NSNumber numberWithUnsignedInt:42U]
  NSNumber *fortyTwoLong = @42L;        // equivalent to [NSNumber numberWithLong:42L]
  NSNumber *fortyTwoLongLong = @42LL;   // equivalent to [NSNumber numberWithLongLong:42LL]

  // floating point literals.
  NSNumber *piFloat = @3.141592654F;    // equivalent to [NSNumber numberWithFloat:3.141592654F]
  NSNumber *piDouble = @3.1415926535;   // equivalent to [NSNumber numberWithDouble:3.1415926535]

  // BOOL literals.
  NSNumber *yesNumber = @YES;           // equivalent to [NSNumber numberWithBool:YES]
  NSNumber *noNumber = @NO;             // equivalent to [NSNumber numberWithBool:NO]

#ifdef __cplusplus
  NSNumber *trueNumber = @true;         // equivalent to [NSNumber numberWithBool:(BOOL)true]
  NSNumber *falseNumber = @false;       // equivalent to [NSNumber numberWithBool:(BOOL)false]
#endif
}

#define INT_MAX   2147483647  /* max value for an int */
#define INT_MIN   (-2147483647-1) /* min value for an int */