iter-group

A trivial library to extend (key, value) iterators with a method that returns a mapping type whose keys are grouped into some collection of type value.

Essentially, it replaces this:

let a = [(1, 'a'), (2, 'b'), (3, 'c'), (2, 'd'), (1, 'e'), (1, 'f')];
let mut map: HashMap<_, Vec<_>> = HashMap::default();
for (k, v) in a.into_iter() {
    map.entry(k).or_default().push(v);
}

with this:

use iter_group:::IntoGroup;
let a = [(1, 'a'), (2, 'b'), (3, 'c'), (2, 'd'), (1, 'e'), (1, 'f')];
let map = a.into_iter().group::<HashMap<_, Vec<_>>>();

See the documentation for additional examples.