%{
#include <stdio.h>
#include <string.h>
void yyerror( const char *msg);	/* called for parser syntax error */
int yylex( void);		/* declare to avoid gcc warnings */
%}

%token INTEGER

%start expression

%%
primary_expression:
	INTEGER 		{ $$ = $1; /* don't need this, $$=$1 is the default action */ }
	| '(' expression ')'	{ $$ = $2; }
	;
	
multiplicative_expression:
	primary_expression
	| multiplicative_expression '*' primary_expression	{ $$ = $1 * $3; }
	;

additive_expression:
	multiplicative_expression
	| additive_expression '+' multiplicative_expression	{ $$ = $1 + $3; }
	;

expression:
	additive_expression 	{ printf( "%d\n", $1); }
	;
%%

int main( int argc, char *argv[])
{
  return yyparse();
}