An unordered multiset/bag implementation backed by HashMap.

A bag, unlike a set, allows duplicate values, and keeps track of how many
duplicates each value holds. This type of collection is often referred to
as an unordered multiset (see also C++'s std::unordered_multiset).

License

Licensed under either of

  - Apache License, Version 2.0
    (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
  - MIT license
    (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted
for inclusion in the work by you, as defined in the Apache-2.0 license, shall be
dual licensed as above, without any additional terms or conditions.
