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` (or `#elseif`).
Similar to `#ifdef` (or `#elseifdef`) 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`
- `#elseifdef`
- `#elseifndef`
- `#endif`
- `#ifdef`
- `#ifndef`
- `#undef`