[m-users.] Typeclasses question

[Volker Wysk]

Am Dienstag, dem 21.10.2025 um 08:44 +0200 schrieb Volker Wysk:
> Hi!
> 
> In Haskell, not only types can be members of a typeclass, but also type
> constructors. Here's an example:
> 
> https://downloads.haskell.org/ghc/latest/docs/libraries/base-4.21.0.0-8bb5/Data-Functor.html
> 
> I want to build this typeclass, following the Haskell typeclass "Functor":
> 
> :- typeclass functor(A) where [
>     func fmap(func(X) = Y, A(X)) = A(Y)
> ].
> 
> "A" is a type constructor. 
> 
> With this, you could do, for instance:
> 
> fmap(func(X) = X+1, maybe(2))
> 
> and get maybe(3).

... no, I mean:

fmap(func(X) = X+1, yes(2))

and get yes(3).

V.