%{

#include <stdio.h>
#include <string.h>

int yylex (void);
void yyerror (char const *);

%}

%union {
	int b;	
	int n;
	char* str;
}

%token <str> CONST
%token <n> NUM
%left EQ NEQ GE LE GT LT
%left '|' '&' '^'
%left '!'
%type <b> boo

%%
input:	/* empty */
	| input line
;

line:	'\n'
	| boo '\n'	 	{ printf("%s\n",$1?"true":"false"); }
	| error '\n' 		{ yyerrok; }
;

boo:	 CONST EQ CONST 	{ $$ = ! strcmp($1, $3); }
	| CONST NEQ CONST 	{ $$ = !! strcmp($1, $3); }
	| NUM EQ NUM		{ $$ = $1 == $3 }
	| NUM NEQ NUM		{ $$ = $1 != $3 }
	| NUM GE NUM		{ $$ = $1 >= $3 }
	| NUM LE NUM		{ $$ = $1 <= $3 }
	| NUM GT NUM		{ $$ = $1 > $3 }
	| NUM LT NUM		{ $$ = $1 < $3 }
	| boo '|' boo 		{ $$ = $1 || $3 }
	| boo '&' boo		{ $$ = $1 && $3 }
	| boo '^' boo		{ $$ = ($1 || $3) && !($1 && $3) }
	| '!' boo		{ $$ = ! $2 }
;

;
%%

#include <ctype.h>
#include <stdlib.h>

#define BUFSIZE 4096

int
yylex(void)
{

	int i, c, last;
	
	while ((c = getchar ()) == ' ' || c == '\t');
	
	if (c == '"'){
		last = '"';
		i = 0;
		if (!(yylval.str = malloc(BUFSIZE))){
			puts("Low memory");
			exit(0);
		}
		while ((c = getchar()) != '"' || last == '\\'){
			yylval.str[i] = c;
			last = c;
			i++;
			if (i >= BUFSIZE-1)
				break;
		}	
		yylval.str[i] = '\0';
	
		return CONST;	
	}

	if (isdigit(c)){
		ungetc(c,stdin);
		scanf("%d",&yylval.n);
		return NUM;
	}

	if (c == '!'){
		if ((c = getchar ()) == '=')
			return NEQ;
	}

	if (c == '<'){
		if ((c = getchar ()) == '=')
			return LE;
		else
			return LT;
	}

	if (c == '>'){
		if ((c = getchar ()) == '=')
			return GE;
		else
			return GT;
	}

	if (c == '='){
		if ((c = getchar ()) == '=')
			return EQ;
	}
	
	if (c == EOF)
		return 0;
	
	return c;
}

void
yyerror (char const *s)
{
	fprintf (stderr, "%s\n", s);
}

int
main(void)
{
	return yyparse ();
}