= Supported Preprocessor Directives =
[wiki:FortranOverview#a1.1.Basicgoals Back:FortranOverview]
== Supported preprocessor directive list ==
* `#include` : Header file inclusion
* `#define` : Macro expansion
* `#error` : Preprocessor error report
* `#ifdef` : Conditional compilation based on macro with definitions
* `#ifndef` : Conditional compilation based on macro without definitions
* `#if` : Conditional compilation based on conditional expressions
* `#elif` : Conditional compilation based on conditional expressions
* `#else` : Conditional compilation based on conditional expressions
* `#endif` : End mark of conditional compilation area.
== A FORTRAN example ==
* File1: macros.h
{{{
#ifdef ERR
#error 'ERR is defined.'
#endif
#define MSG_HW "Hello World!"
#define MSG_HI "Hi, "
#define MSG_BW "Bye World!"
#define MSG_NM ".."
#ifndef NAME
#define NAME "FORTRAN"
#endif
}}}

* File2: preproc.f
{{{
#include "macros.h"

C      A Fortran program example used for testing that
C      ABC shall correctly handle C preprocessor directives
C      defined in Fortran source code.
C      Directives are used mainly for two purposes:
C        1. User-specified conditional compilation
C        2. Macro expansion / String substitution
C      Directives tested here are: 
C        "include", "define", "undef", "if", "ifdef", "ifndef"
C        "error"

       program HelloWorld
#if NUM_MSG==1
          print *, MSG_HW
#elif NUM_MSG==2
          print *, MSG_HW
          print *, MSG_HI, NAME
#elif NUM_MSG>=3
          print *, MSG_HW
          print *, MSG_HI, NAME
#ifdef BYE
          print *, MSG_BW
#undef BYE
#endif
#ifdef BYE
#error "BYE should be undefined." 
#endif
#else
          print *, MSG_NM
#endif
       end

}}}