%union{
  int int_val;
}

%left '+', '-'
%left '*', '/'
%left UMINUS

%token <int_val> INT
%type <int_val> expr

%start program

%%

program : stmt_list 
        | error         {printf("YACC: syntax error near line %d \n", linenum);
                         abort();}
        ;

stmt_list : stmt_list stmt
          | stmt
          ; 

stmt : expr ';'     {printf("Expr value = %d \n", $1);} 
     ;

expr : '(' expr ')'      {$$ = $2;}
     | expr '+' expr     {$$ = $1 + $3;}
     | expr '-' expr     {$$ = $1 - $3;}
     | expr '*' expr     {$$ = $1 * $3;}
     | expr '/' expr     {$$ = $1 / $3;}
     | '-' expr          %prec UMINUS {$$ = -$2;}
     | INT               {$$ = $1;}
     ;

%%

#include "lex.yy.c"