%{
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>

int yylex() ;

void yyerror(const char *s) {
   fprintf(stderr, "yyerror: %s\n", s) ;
   exit(1) ;
}

FILE *of ;
%}
%token NAME NUMBER
%%

expression: expression '+' NUMBER   { fprintf (of, "%d + ", $3) ; } 
    |       expression '-' NUMBER   { fprintf (of, "%d - ", $3) ; }
    |       NUMBER                  { fprintf (of, "%d ", $1) ; }
    ;
%%

int main () {

   fprintf (stderr, "Enter an expression:\n") ;
   of = fopen ("out.fs", "w") ;
   assert(of != NULL) ;

   yyparse() ;

   fprintf (of, "\n.s CR\n") ;

   fclose(of) ;
   return 0 ;
}  /* End of main() */