%{
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#include "ast.h"
#define YYSTYPE struct ast *

#include "y.tab.h"

int yylex(void);

void yyerror(struct ast **result, const char *str)
{
        fprintf(stderr, "error: %s\n", str);
}

int yywrap()
{
        return 1;
}

%}

%token INTEGER PLUS MINUS TIMES DIVIDE BOPEN BCLOSE SEMICOLON
%parse-param { struct ast **result }

%%

start : exprs { *result = $1; } ;

exprs
	: { $$ = NULL; }
	| exprs expr SEMICOLON { $$ = ast_cons($2, $1); }
	;

expr
	: expr PLUS fact { $$ = ast_binop($1, plus, $3); }
	| expr MINUS fact { $$ = ast_binop($1, minus, $3); }
	| fact
	;

fact
	: fact TIMES basic { $$ = ast_binop($1, times, $3); }
	| fact DIVIDE basic { $$ = ast_binop($1, divide, $3); }
	| basic
	;

basic
	: INTEGER
	| BOPEN expr BCLOSE { $$ = $2; }
	;