[Haskell-cafe] FunDeps conflict
bjornson at dtek.chalmers.se
Tue Jun 6 05:38:40 EDT 2006
I have a question regarding type classes and FunDeps.
Consider the following code :
> class Class2 a b | a -> b
> class IsFoo a
> data Bar a = Bar a
> instance IsFoo a => Class2 a a
> instance IsFoo a => Class2 (Bar a) a
The last two instantiations will yield a 'Functional dependencies conflict
error'. From what I understand, this is because (Bar a) *MAY* instantiate
the type class isFoo, which would obviously lead to a conflict between the
Is there anyway to get around this, knowing that (Bar a) won`t instantiate
the isFoo class, or is the right answer simply to get rid of the FunDep ?
More information about the Haskell-Cafe