Function natural 

pub fn natural(a: &str, b: &str) -> Ordering

Compares two strings using natural sort order. Natural sort order compares numbers in a way humans expect, so “swp10” comes after “swp2” instead of “swp10” being less than “swp2” as in ASCII sorting.

Arguments

• a: The first string to compare.
• b: The second string to compare.

Returns

An Ordering indicating the result of the comparison.