[Haskell-cafe] DiffArray is an unsaturated type?

[Neil Mitchell]

Hi,

I note that in the base libraries, Data.Array.Diff is defined as:

type DiffArray  = IOToDiffArray IOArray

However, IOToDiffArray takes 3 parameters.

I thought this was not allowed in Haskell 98? Its annoying from my
point of view because Hoogle wants to know the arity of a type, and if
it has to chase down the arity of the RHS to do it, I probably just
won't bother.

Is there any difference between the above definition and:

type DiffArray a b = IOToDiffArray IOArray a b

Is the first prefered for any reason?

Thanks

Neil