Function sqrt 

pub fn sqrt<T: PrimInt + CheckedShl + CheckedShr>(radicand: T) -> Option<T>

Calculate square root of the given number

Code lovingly adapted from the excellent work at:

https://github.com/derekdreery/integer-sqrt-rs

The algorithm is based on the implementation in:

https://en.wikipedia.org/wiki/Methods_of_computing_square_roots#Binary_numeral_system_(base_2)