changeset-containers

Stateful monad transformer based on monoidal actions.

A general state monad transformer with separate types for the state and the possible changes. It can be defined for any monoid action. The monoid represents "changes", "updates", "edits" or "diffs" on the state. This package exposes typical changes for containers such as maps, sequences, and sets. To change individual elements of a container, have a look at the indexed changes in @changeset-lens@.