Crate bit_combi_iter

This 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;

let mut c = BitCombinations::new(0b00010100u8);

// Iterates all bit combinations less than 0b10100
assert_eq!(c.next().unwrap(), 0b00010010);
assert_eq!(c.next().unwrap(), 0b00010001);
assert_eq!(c.next().unwrap(), 0b00001100);
assert_eq!(c.next().unwrap(), 0b00001010);
assert_eq!(c.next().unwrap(), 0b00001001);
assert_eq!(c.next().unwrap(), 0b00000110);
assert_eq!(c.next().unwrap(), 0b00000101);
assert_eq!(c.next().unwrap(), 0b00000011);

// After iterating all combinations, the iterator reaches the end
assert!(c.next().is_none());

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)
let mut c = BitCombinations::new(0b11100u8);
assert_eq!(c.next().unwrap(), 0b11010);
assert_eq!(c.next().unwrap(), 0b11001);
assert_eq!(c.next().unwrap(), 0b10110);
assert_eq!(c.next().unwrap(), 0b10101);
assert_eq!(c.next().unwrap(), 0b10011);
assert_eq!(c.next().unwrap(), 0b01110);
// ...

The algorithm was borrowed from the blog post by @herumi.

Structs

BitCombinations

An iterator to iterate all bit combinations less than given unsigned integer value keeping 1s in the bits. The U type parameter can be u8, u16, u32, u64 or u128 primitive types. Size of this struct is exactly the same as size of U.

Traits

UIntExt

A trait to implement the same algorithm for multiple unsigned integer types. u8, u16, u32, u64 and u128 types already implement this trait.