Here is a code generation example using MDef
(http://mdef.sourceforge.net):
  
  mdef program
      program-headers
      program-main
  mend
  
  mdef program-headers
      #include <stdio.h>
  mend
  
  mdef program-main
      int main(int argc, char* argv[])
      {
          program-body
      }
  mend
  
  mdef program-body
      printf("hello world\n");
      return 0;
  mend
  
  program
  
Save this to hello.m. Then type 

  perl mdef.pl hello.m > hello.c 
  gcc hello.c 
  ./a.out

This will print "hello world".

Note that everything here is reusable except for the program-body.