defined

Preprocessor function to test if a symbol has been defined

Syntax
   defined (symbol_name)

Parameters
   symbol_name
      Name of the symbol to test

Return Value
   Returns non-zero (-1) if the symbol has been defined, otherwise returns 
   zero (0).

Description
   Given the symbol name, the defined() preprocessor function returns true 
   if the symbol has been defined - or false if the symbol is unknown.

   This is used mainly with #if.

   Similar to #ifdef except it allows more than one check to occur because 
   of its flexibility.

Example
   'e.g. - which symbols are defined out of a, b, c, and d ?

   Const a = 300
   #define b 12
   Dim c As Single

   #if defined(a)
    Print "a is defined"
   #endif
   #if defined(b)
    Print "b is defined"
   #endif
   #if defined(c)
    Print "c is defined"
   #endif
   #if defined(d)
    Print "d is defined"
   #endif

Differences from QB
   * New to FreeBASIC

See also
   * #define
   * #macro
   * #if
   * #else 
   * #elseif 
   * #endif 
   * #ifdef
   * #ifndef
   * #undef

