Re: [Haskell-beginners] Fwd: Re: Multiple letters between -> ->

30 Nov 2017


      Hello Marcus,

On Thu, Nov 30, 2017 at 12:37:12PM +0100, Marcus Manning wrote:
...
2.) How do I define a function which takes a 3-Kinded Type:
let f:: h (g a); f a = a
where g * -> * and h (*->*)->*, but it did not work as:
h is deduced to be h * -> *.
h hasn't got kind * -> * -> *, as Maybe hasn't got kind * -> * -> *
but * -> *. A simple type constructor like the one you are searching
for is Either

    λ> :k Either
    Either :: * -> * -> *

or a tuple

    λ> :k (,)
    (,) :: * -> * -> *

Re: [Haskell-beginners] Fwd: Re: Multiple letters between -> ->

Francesco Ariis