====== Preprocessing ======

Many programming languages feature a preprocessor that processes macros, allows conditional compilation based on certain criteria, etc.

XC=BASIC doesn't have a preprocessor, but you can use a third-party (generic) preprocessor as part of your toolchain.

This guide guide advises using [[https://logological.org/gpp|GPP, a general-purpose preprocessor]].

===== Using GPP with XC=BASIC =====

To run GPP before the input is passed to XC=BASIC, you can use piping:

  gpp -n source.bas | xcbasic3 /dev/stdin result.prg

What it does is call GPP first, then pass its output to XC=BASIC that does the rest.




===== Examples =====

The simplest example is defining a macro and creating a conditional block:

  REM #define TARGET c64
  
  REM #ifeq TARGET plus4
  CONST BGCOLOR = $FF15
  REM #else
  CONST BGCOLOR = $D021
  REM #endif
  
  POKE BGCOLOR, 0

<adm note>
To make code more readable and not to confuse your syntax highlighter, is it advised that you put preprocessor metacommands in XC=BASIC comments, like in the example above.
</adm>