[Haskell-cafe] Proposal: (.:) operator in base.

[Alex Belanger]

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 at 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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