#ifndef
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## #ifndef

#ifndef — Conditional reading of code.

## Description

Macros are textual replacements which are made in the orchestra as it is being read. The orchestra macro system in Csound is a very simple one, and uses the characters # and $ to define and call macros. This can save typing, and can lead to a coherent structure and consistent style. This is similar to, but independent of, the macro system in the score language.

If the specified macro is not defined then #ifndef can incorporate text into an orchestra upto the next #end.

## Syntax

    #ifndef NAME

    ....

    #else

    ....

    #end

## Performance

Note that the #ifndef can be nested, like in the C preprocessor language.

## Examples

Here is a simple example of the conditional.

Example 18. Simple example of the #ifndef form.

              #define final ##
              instr 1
              #ifndef final
              print "calling oscil"
              #end
              a1   oscil 32000,440,1
              out  a1
            endin

## See Also

#define, $NAME, #ifdef, #include, #undef

## Credits

Author: John ffitch
University of Bath/Codemist Ltd.
Bath, UK
April 2005

New in Csound5 (and 4.23f13)

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