%{
#include <stdio.h>
#include <ctype.h>
#include <math.h>
#define YYSTYPE int /* integere type for YACC stack */

%}

%token NUMBER
%token ERROR
%token '('
%token ')'
%left '+' '-'
%left '*' '/'
%right UMINUS

%%
lines   :  lines expr '\n'        {printf("%d\n", $2);}
        |  lines '\n'
        |  /* empty */
        |  lines error '\n' { yyerror("Please reenter:"); yyerrok; }
        ;
expr    :  expr '+' expr    { $$ = $1 + $3; }
        |  expr '-' expr    { $$ = $1 - $3; }
        |  expr '*' expr    { $$ = $1 * $3; }
        |  expr '/' expr    { $$ = $1 / $3; }
        |  '(' expr ')'     { $$ = $2; }
        |  '-' expr  %prec UMINUS  { $$ = - $2; }
        |  NUMBER { $$ = atoi(yytext);}
        ;

%%
#include "lex.yy.c"