Function broadword::select1

pub fn select1(r: usize, x: u64) -> Option<usize>

Finds the index of the rth one bit in x.

Uses the broadword algorithm from Vigna. Note that bits are numbered from least-significant to most.

Examples

use broadword::select1;

assert_eq!( select1(0, 0x0000_0000_0000_0000), None );
assert_eq!( select1(0, 0x0000_0000_0000_0001), Some(0) );
assert_eq!( select1(0, 0x0000_0000_0000_0002), Some(1) );
assert_eq!( select1(0, 0x0000_0000_0000_0004), Some(2) );
assert_eq!( select1(2, 0x0000_0000_0000_0004), None );
assert_eq!( select1(2, 0x0000_1010_1010_0114), Some(8) );
assert_eq!( select1(3, 0x0000_1010_1010_0114), Some(20) );
assert_eq!( select1(4, 0x0000_1010_1010_0114), Some(28) );