gistfile1.txt

extern crate bit_vec;
use bit_vec::BitVec;
use std::ops::Add;
use std::ops::Sub;


fn twos_comp(mut bv: BitVec) {
    let mut one = BitVec::from_elem(bv.len(), false);
    one.set(0) = true;
    bv.negate();
    bv = bv_add(bv, one);
    bv;
}

fn assign(mut bv: BitVec, other: i32) {
    let neg = other < 0;
    let other = other.abs();
    let mut to_add = other;
    let mut pow = 256;
    while pow >= 0 {
        if 2^pow < other {
            to_add = to_add - 2^pow;
            bv.set(pow, true);
        }
    }
    if neg {
        bv.twos_comp();
    }
    bv;
}

fn bv_add(bv: BitVec, other: BitVec) {
     assert_eq!(bv.len(), other.len());
     let mut bit = 0;
     let mut carry = false;
     while bit < bv.len() {
         if bv.get(bit) == Some(true)
            && other.get(bit) == Some(true)
            && carry == Some(true) {
             bv.set(bit) = true;
             carry = true;
         }
         else if bv.get(bit) == Some(false)
            && other.get(bit) == Some(true)
            && carry == Some(true) {
             bv.set(bit) = false;
             carry = true;
         }
         else if bv.get(bit) == Some(true)
            && other.get(bit) == Some(false)
            && carry == Some(true) {
             bv.set(bit) = false;
             carry = true;
         }
         else if bv.get(bit) == Some(false)
            && other.get(bit) == Some(false)
            && carry == Some(true) {
             bv.set(bit) = true;
             carry = false;
         }
         else if bv.get(bit) == Some(true)
            && other.get(bit) == Some(false)
            && carry == Some(false) {
             bv.set(bit) = true;
             carry = false;
         }
         else if bv.get(bit) == Some(false)
            && other.get(bit) == Some(true)
            && carry == Some(false) {
             bv.set(bit) = true;
             carry = false;
         }
         bit = bit + 1;
     }
     bv;
}


// Two's compliment subtraction is the same
// as the addition operation
fn Sub(mut bv: BitVec, other: BitVec) {
    bv = bv_add(bv,other);
    bv;
}

fn main() {
    println!("Hello, world!");
    let test = BitVec::(256,Some(false));
    let test = assign(test, -24)