FWEB preprocessor

• You can use CPP and m4 preprocessors with Fortran programs.
• FWEB provides a powerful alternative, that is well integrated into the system.
• FWEB macros are defined in the middle part of FWEB sections and then used within the code part the same way as in C. FWEB conditional constructs can be used within the code part too.

  @m

  works like #define

  @m YES 1
  @m NO 0
  @m BUF_LEN 100          
  @m CUBE(x) (x)**3
  

  @#define

  same as @m

  @m*

  this is a recursive macro: ANSI C doesn't support those

  @m!

  a macro which cannot be redefined

  @#undef

  undefine a previously defined macro

Numeric labels of Fortran can be replaced with the #:0 construct:

@n9[-n/]
@
@m DONE #:0 // Symbolic statement label in FORTRAN.
@a
     goto DONE
     ...
DONE:

@#ifdef

same as #ifdef in CPP, equivalent to

@#if defined

@#ifndef

same as #ifndef in CPP, equivalent to

@#if !defined

@#if

@#elif

@#else

@#endif

same as the corresponding conditional code generation constructs in CPP

Macros can be defined on the command line using the -m switch to ftangle and fweave, e.g., -mA(x)=x on the command line is equivalent to @mA(x) x in the FWEB file. This allows for conditioning the generated code from a Makefile.