[Haskell-cafe] Re: newbie : multi-parameter type classes

[Christian Maeder]

Thomas Girod wrote:
> class (Eq n, Eq e) => Topo a n e where
>     empty    :: a

empty does not allow to infer the types n and e

>     nodes    :: a -> [n]

also nodes leaves the type e undetermined

http://www.haskell.org/ghc/docs/latest/html/users_guide/type-extensions.html#functional-dependencies

Unfortunately
http://www.cse.ogi.edu/~mpj/pubs/fundeps.html
is broken.

Christian