Data.Functor.{Product,Sum} functions

[Jon Fairbairn]

Baldur Blöndal <baldurpet at gmail.com> writes:

> Let's see if any of these are useful (a lot more at
> https://ghc.haskell.org/trac/ghc/ticket/13026)
>
> (||||) :: (f a -> b) -> (g a -> b) -> ((Sum f g) a -> b)
> f |||| g = \case
>   InL fa -> f fa
>   InR ga -> g ga
>
> (&&&&) :: (a -> f b) -> (a -> g b) -> (a -> (Product f g) b)
> (f &&&& g) a = f a `Pair` g a
>
> I couldn't think of any for Data.Functor.Compose, names are up for
> bikeshedding

I don’t have any particular preference for names, but I’d say
that any name consisting of more than three consecutive
identical symbols is going to be too hard to read (particularly
if the symbol is “|”). There’s a whole unicode alphabet out
there.

-- 
Jón Fairbairn                                 Jon.Fairbairn at cl.cam.ac.uk