bit_combi_iter

bit_combi_iter is a small dependency-free crate to enumerate all bit combinations less than given unsigned integer value keeping 1s in the bits.

use bit_combi_iter::BitCombinations;

fn main() {
    let u = 0b00010100u8;

    let mut c = BitCombinations::new(u);

    println!("{:#b}", c.next().unwrap()); // => 0b00010010
    println!("{:#b}", c.next().unwrap()); // => 0b00010001
    println!("{:#b}", c.next().unwrap()); // => 0b00001100
    println!("{:#b}", c.next().unwrap()); // => 0b00001010
    println!("{:#b}", c.next().unwrap()); // => 0b00001001
    println!("{:#b}", c.next().unwrap()); // => 0b00000110
    println!("{:#b}", c.next().unwrap()); // => 0b00000101
    println!("{:#b}", c.next().unwrap()); // => 0b00000011
    println!("{}", c.next().is_none()); // => true
}

This crate is useful when you want to enumerate all n bit integers including k ones.

// Enumerate all 5 bit integers including 3 ones (as u8)
BitCombinations::new(0b11100u8)
// 11100
// 11010
// 11001
// 10110
// 10101
// ...

Implementation of this crate is very efficient:

The algorithm to generate the next bit combination consists of only a few arithmetic calculations, bit operations and
shift operations.
Size of BitCombinations<U> is the same as size of U. For example, size of BitCombinations<u8> is 8 bits.