More containers

Multisets

> m1 = fromList [1, 2, 1] :: Multiset Int
> count 1 m -- 2
> m2 = replicate 3 1 -- fromList [1, 1, 1]
> insert 1 m == m2 <> singleton 2 -- True

Multimaps

This library provides both generic and versions specialized to lists, sets, and sequences.

> m1 = fromList [(1, "ab"), (2, "d")] :: ListMultimap Int Char
> m1 ! 1 -- "ab"
> m1 ! 3 -- ""
> m2 = prepend 2 'c' m1 -- fromList [(1, "ab"), (2, "cd")]
> toList m2 -- [(1, 'a'), (1, 'b'), (2, 'c'), (2, 'd')]