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

const int MAX_PROGRAM_LENGTH = 38911;
// FILE* outfile; for compiler.
char* input;
char* token;
char delims[] = " \n\r\t";

void next_token()
{
    static int started = 0;
    if (! started) {
        token = strtok (input, delims);
        started = 1;
    }
    else {
        token = strtok (NULL, delims);
    }
    if (token == NULL) token = "EOF";
}

void error(char* nt)
{
    fprintf(stderr, "Error in %s at token '%s'\n", nt, token);
    exit(1);
}

void Opnd ()
{
    if (! strcmp (token, "true")) {
        next_token();
    }
    else if (! strcmp(token, "false")) {
        next_token();
    }
    else error("Opnd");
}

void Expr ()
{
    if (! strcmp(token,"or")) {
        next_token(); Expr(); Expr();
    }
    else if (! strcmp(token,"and")){
        next_token(); Expr(); Expr();
    }
    else if (! strcmp(token,"exor")){ 
        next_token(); Expr(); Expr();
    }
    else if (! strcmp(token,"not")) {
        next_token(); Expr();
    }
    else Opnd();
}

void Start ()
{
    next_token();
    Expr();
    if (strcmp(token, "EOF")) {
        error("Start");
    }
}

int main(void)
{
    FILE* infile = fopen("in.truth", "r");
    input = malloc(MAX_PROGRAM_LENGTH);
    fgets(input, MAX_PROGRAM_LENGTH, infile);
    Start();
    fclose(infile);
    return 0; 
}