/* calc2.y
 * YACC desk calculator example, adopted from ALSU, sec. 4.9
 * handles double arithmetic, uses lex as scanner
 *
 * to compile, use:
   lex calc2.l
   yacc calc2.y
   gcc -o calc2 y.tab.c -ly
 */

%{
#include <stdio.h>
#define YYSTYPE double
%}

%token NUM

%%
lines	: lines expr '\n'	{ printf("= %g\n", $2); }
	| lines '\n'
	| /* epsilon */
	| error '\n'
	;

expr	: expr '+' term		{ $$ = $1 + $3; }
	| expr '-' term		{ $$ = $1 - $3; }
	| term			{ $$ = $1; /* default rule */ }
	;

term	: term '*' factor	{ $$ = $1 * $3; }
	| term '/' factor	{ $$ = $1 / $3; }
	| factor
	;

factor	: '(' expr ')'		{ $$ = $2; }
	| NUM
	;

%%

#include "lex.yy.c"