%{

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

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

%}

%union {
	int b;	
	char* str;
}

%token <str> CONST
%left EQ
%left '|' '&' '^'
%left '!'

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

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

boo:
	CONST EQ CONST 	{ $$ = ! strcmp($1, $2); } 
	| boo EQ boo 		{ $$ = $1 == $2 } 
	| boo '|' boo 		{ $$ = $1 || $2 }
	| boo '&' boo		{ $$ = $1 && $2 }
	| boo '^' boo		{ $$ = ($1 || $2) && !($1 && $2) }
	| '!' boo		{ $$ = ! $1 }
;

;
%%

#include <ctype.h>

#define BUFSIZE 4096

int
yylex(void)
{

	int c, last;
	char temp[BUFSIZE];
	char* p=temp;
	
	while ((c = getchar ()) == ' ' || c == '\t');
	
	if (c == '"'){
		last = '"';
		while ((c = getchar()) != '"' || last == '\\'){
			*p = c;
			last = c;
			p++;
			if (p-temp >= BUFSIZE-1)
				break;
		}	
		*p = '\0';
	
		strcpy(&yylval,temp);
		return CONST;	
	}

	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 ();
}