%{
 /* C declarations */
#define YYSTYPE double
#include <stdio.h>
#include <stdlib.h>
  
void yyerror(char* s) {
   printf("%s\n", s);
}

int yylex(void); /* prototype declaration */
%}
/* Bison declarations */ 
%token NUMBER
%token FOO
%left '+' '-' FOO
%left '*' '/' 
%%
input :   /* empty */
      | input line    {}
      ;
line  : '\n'          { exit (0); }  /* exit with an empty line */
      | expr '\n'     { printf ("\t%g\n", $1); }
      ;
expr :  NUMBER        { $$ = $1; }
      | expr FOO expr { $$ = $1 * 256 + $3; }
      | expr '+' expr { $$ = $1 + $3; }
      | expr '-' expr { $$ = $1 - $3; }
      | expr '*' expr { $$ = $1 * $3; }
      | expr '/' expr { $$ = $1 / $3; }
      | '(' expr ')'  { $$ = $2; }
      ;
%%
int main(void) {
   printf("Exit with Ctrl-c.\n");
   yyparse();
   return 0;
}