1 %{
 2  #include <stdlib.h>
 3  #include "parser.tab.h"  // generated by bison; includes macros, tokens (e.g. NUMBER)
 4  extern int yylval;       // necessary for grammar variables
 5 %}
 6
 7 %%
 8
 9 "+" |
10 "-" |
11 "*" |
12 "/" |
13 "(" |
14 ")" |
15 "%"      { return yytext[0]; } 
16 "\n"     { return yytext[0]; }
17
18 [0-9]+   { yylval = atoi(yytext);
19            return NUMBER; }