Oh, Agda. Didn't realise the kata was available in multiple languages, sorry.

What?

language?

The open Language {{...}} line in the template should be made public so that the tests work.

I see. RankNTypes should be made available for TupleSections to work. The above error will occur when {-# LANGUAGE RankNTypes #-} is missing. Sorry for the stupid question.

How to avoid the following error on the test case Cannot use Control.Lens? I did not import anything that relates to Control.Lens.

uncaught exception: IOException of type UserError
user error (Could not parse solution correctly)

Also known as a difference list. If you're looking for hints, Hughes lists, when run, will not overwrite the list they take as an input.

Very scary, but surprisingly pretty easy, just follow the types (some of them are singletons !)

Really nice kata, thanks tel !

It is satisfctory, but I wish it could give more thorough explanation and type replacements.
Especially, how each part of it works. (And what actually is a profunctor)

[...] suggests that it receives a function (Name -> Maybe String) and returns another function (Phalanx -> Maybe String)

which is true with and without the parentheses because of Haskell's autocurrying. But I agree that the parentheses should be omitted as they do nothing.

what's mean a type? use not a

newtype K b a = K { getK :: b } deriving Functor

Very nice. Managed to follow almost all of it, but still don't quite get prisms. Follow the types!

It would be nice if the declaration of interp was changed to interp :: (Name -> Maybe String) -> Phalanx -> Maybe String as the current one suggests that it receives a function (Name -> Maybe String) and returns another function (Phalanx -> Maybe String).

Needs random tests

Done.

All existing solutions invalidated - they need a split Monoid instance as well.

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