[Haskell-cafe] DiffArray is an unsaturated type?

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