How to write Haskell style code assuming type classes ?

[MarcWeber]

In Haskell you can do

foo: Show a; a -> IO ()
foo = print . show
-- same as  foo a = print (show a)

How would such be done with classy ? I am still new to nim.
The point is thaht Show is the typeclass and a is the type parameter.

[nigredo-tori]

The best this library can give you at the moment is probably something like this (assuming print is defined elsewhere):

typeclass Show, A:
  # proc show(a: A): string

proc foo[A](a: A) = print(show(a))

Show doesn't actually do anything here, though. At the moment, imposing actual typeclass constraints is not supported. I toyed with the idea, but couldn't figure how to find some kind of canonical and unique representation for a type, without which the whole thing seems impossible.

As an improvement to the above It's possible we can uncomment show declaration in the typeclass (I heard the corresponding issue got squished some time ago). You can also try and write a concept for Show that would check that show(a) compiles, which can be checked in the signature.