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

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