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