Non-Bijective Two-Way Dictionary

[ColmBhandal]

Requirement

Add a two way dictionary that acts as a regular dictionary but also allows you to efficiently retrieve in constant time the set of values mapping to a given value.

Value Proposition

This is useful in various processing operations where we want to be able to loop over linked sets in different ways.

Design Ideas

There should be a set-valued Inverse property, a set-valued dictionary, which would be added to in the background as you add to the original, and cleared when you clear the original- similar for remove or any other mutators.