Considering this would be in Data.Function along (.) and ($), I do not think generalizing it is the goal. The aim should be to keep it for functions only... or at least, that's how I've seen (.:) used so far. I'm all ears though. This is already getting interesting. On Wed, Aug 17, 2016 at 7:53 PM, MarLinn via Haskell-Cafe < haskell-cafe@haskell.org> wrote:
Some of you might be familiar with (.:) = (.) . (.).
It has type :: (c -> d) -> (a -> b -> c) -> a -> b -> d
First of all, I always called it "dot". Don't know where I picked that one up, though. (.:) looks like it could conflict with some lens or something. Would need checking.
Also, which version? This simple one? Or the Category one?
(.).(.) :: (Category cat) => cat c d -> (a -> cat b c) -> a -> cat b d
I know little about Category Theory, but throwing together some random words I collected over time that looks like... a "contravariant bind in the monad of endocategories", maybe? I just invented that and it's almost certainly meaningless gibberish, but knowing our community it might well be that *there's a lib for that*. Also, why is
h = f .: g == (f .) . g
not good enough?
So many questions, so much bikeshedding to do, so little time...
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