Function iter_set::difference

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

Take the difference of two sets (elements in a but not in b) represented by sorted, deduplicated iterators.

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