Often when working with the containers offered by the containers and unordered-containers packages one would prefer the monoidal structure of the values to be used when resolving conflicts between keys when merging structures. Sadly, these are not the semantics offered by the provided instances. This package provides newtypes with an appropriate set of instances and utility functions to make them usable.

This library is designed to be a drop-in replacement for Data.Map and similar. Absolutely no other semantic changes are introduced in functions like fromList or insert. They are still left-biased like Data.Map's. The only difference is in instances for Semigroup.