%{
#include <stdio.h>
#include "symtable.h"

void emit(char*, char*);
%}

%union {
	int value;
	int index;
	char relop;
}

%token <value> NUMBER
%token <index> ID
%token <relop> RELOP
%token ASSIGN
%token IF THEN ENDIF

%left RELOP
%left '-' '+'
%left '*' '/'

%type <value> expr
%%

program	:	stmt_list
	;

stmt_list :	stmt_list ';' stmt
	|	stmt
	;
	
stmt	:	ID {emit("lvalue", get_id($1));} ASSIGN expr {emit(":=", ""); }
	|	IF expr THEN stmt_list ENDIF
	;

expr	:	expr '+' expr		{ emit("add", ""); }
	|	expr '-' expr		{ emit("sub", ""); }
	|	expr '*' expr		{ emit("mul", ""); }
	|	expr '/' expr		{ emit("div", ""); }
	|	expr RELOP expr		{ if($2 == '=') emit("eq", ""); else
					  if($2 == '<') emit("lt", ""); else
					  if($2 == '>') emit("gt", ""); }
	|	'(' expr ')'		{}
	|	NUMBER			{ emit_i("push", $1); }
	|	ID			{ emit("rvalue", get_id($1)); }
	;
	
%%

yyerror(char* errmsg)
{
	extern char* yytext;
	fprintf(stderr, "%s (%s)\n", errmsg, yytext);
}

void emit(char* opcode, char* operand)
{
	printf("> %s %s\n", opcode, operand);
}

void emit_i(char* opcode, int operand)
{
	printf("> %s %d\n", opcode, operand);
}

main(int argc, char** argv)
{
	initlex();
	yyparse();
	return 0;
}