TODO: Stuff

Stuff.markdown

Free category is ubiquitous

https://github.com/kylcarte/derivation/blob/21776455a80c57db14276a6477486fc78cf9018f/src/Data/Evaluation.hs#L26

A tutorial on the universality and expressiveness of fold

uses

fold :: (α → β → β) → β → ([α] → β)

instead of

fold :: (a -> b -> b) -> b -> [a] -> b
-- or
fold :: (a -> b -> b) -> (b -> [a] -> b)