Function union 

pub fn union<T, L, R>(a: L, b: R) -> impl Iterator<Item = T>
where
    T: Ord,
    L: IntoIterator<Item = T>,
    R: IntoIterator<Item = T>,

Take the union of two sets represented by sorted, deduplicated iterators.

If an element is in both iterators, then only the one from a is yielded. This behaviour can be overridden by using union_by().

Time complexity: O(a.len() + b.len()).

Examples

use iter_set::union;

let a = [1, 2];
let b = [2, 3];

assert!(union(&a, &b).eq(&[1, 2, 3]));