[notduncansmith]

This reminds me a lot of a library I wrote called Factfold (https://github.com/notduncansmith/factfold).

Something I noticed while working on it is that the declarative style is not always the most comfortable way to describe things, and well-written imperative code is declarative in its own way. Somewhere in most useful programs, it helps to have the imperative escape hatch until you can support the best declarative expression.