use std::io::{self, Read, Write};

fn xor(x: char, y: char) -> char {
    // Rust lacks the ternary operator.
    // Since if-blocks are expressions, it'd be redundant.
    if x != y { '1' } else { '0' }
}

fn or(x: char, y: char) -> char {
    if x == '1' || y == '1' { '1' } else { '0' }
}

fn and(x: char, y: char) -> char {
    if x == '1' { y } else { '0' }
}

/// Add the new bits together, returning the result and the carry out
fn bit_adder(x: char, y: char, carry: char) -> (char, char) { // Eat my tuple, C
    let half_out = xor(x, y);
    let half_carry = and(x, y);
    let out = xor(half_out, carry);
    let carry = or(half_carry, and(half_out, carry));

    (out, carry)
}

fn adder(left: [char; 8], right: [char; 8]) -> [char; 8] {
    // Array initializer
    let mut out = ['0'; 8];
    let mut carry = '0';

    for i in (0 .. 8).rev() {
        let (new_out, new_carry) = bit_adder(left[i], right[i], carry);
        out[i] = new_out;
        carry = new_carry;
    }

    out
}

fn read_binary() -> [char; 8] {
    let mut stdin = io::stdin();

    let mut out = ['0'; 8];
    let mut buf = String::new();

    let _ = stdin.read_line(&mut buf).unwrap();

    for (ch, left_ch) in buf.trim().chars().zip(out.iter_mut()) {
        *left_ch = ch;
    }

    out
}

fn print_flush(st: &str) {
    print!("{}", st);
    io::stdout().flush().unwrap();
}


fn main() {
    print_flush("Enter the first number: ");
    let left = read_binary();

    print_flush("Enter the second number: ");
    let right = read_binary();

    let out = adder(left, right);

    print!("Result: ");

    for &ch in out.iter() {
        print!("{}", ch);
    }

    println!("");
}