c    J. Wallin 2002
c
c  A sample code using macros
c
c To use this code, 
c 1) type "cpp -P macro.f"   This will show
c    you the effects of the cpp on the file.
c
c 2) type "cpp -P -Ddebug macro.f"  This will show
c    you the effects of the cpp on the file with
c    debug defined.
c 
c 3) type "cpp -P -Ddebug macro.f > m.f" to preprocess
c    with the debug flag and direct the out put to the file
c    "m.f"
c
c 4) use the f77 (not the f90) compiler to compile the
c    code.   If you use f90, it gets confused.
c

#define mult(a,b) ((a)*(b))
#define nsize 30

      program test
      double precision  x, y, z
c     declaration using define
      real g1(nsize)

      x = 1
      y = 2

c     a macro based function
      z = mult(x,y)

c     macro based debugging
#ifdef debug
      print*,z
#endif      
      call duck(g1)

      stop
      end

      subroutine duck

      real g(nsize)


      return
      end