qfpl / hedgehog-fn Goto Github PK

I want something like

data NT :: (Type -> Type) -> (Type -> Type) -> Type
appNT :: NT f g -> f a -> g a

and some way to generate arbitrary values of type NT f g. Any idea how this might be done?

There were a couple of questions in the reddit thread about this kind of idea.

I think it's cool but I don't know if it's possible. The main example of monotonicity requires knowledge of the entire domain and codomain, which isn't captured by a -> Gen b anyway. At the very least we need to be aware of the history of inputs to the function.

The memo-trie approach works by lazily enumerating all the possible inputs to the function, so if we wanted to generate a monotonic function then somehow each input would have to have a knot that knows about all the other inputs. I don't know that it works.