%{
void yyerror( char * );
%}
%token NUM
%token PLUS MINUS MULT DIV
%token LPAR RPAR
%%
input: expr ’\n’ { printf ("ans = %d\n", $1); }
| input ’\n’
|
;
expr: expr PLUS term { $$ = $1 + $3; }
| expr MINUS term { $$ = $1 - $3; }
| term
;
term: term MULT factor { $$ = $1 * $3; }
| term DIV factor { $$ = $1 / $3; }
| factor
;
factor: LPAR expr RPAR { $$ = $2; }
| NUM { $$ = $1; }
;
%%
int main ()
{
yyparse ();
return 0;
}
void yyerror(char * e)
{
printf ("--- Error --- %s\n", e);
}
-_-_-
%{
#include "prog.tab.h"
%}
%%
"\n" return ’\n’;
"+" return PLUS;
"-" return MINUS;
"*" return MULT;
"/" return DIV;
"(" return LPAR;
")" return RPAR;
[0-9] { sscanf(yytext,"%d",&yylval);
return NUM;}
-_-_-
