Re: [Haskell-cafe] Classes in type declarations in Hugs

On 2004 November 30 Tuesday 11:04, John Goerzen wrote:

type CPResult a = MonadError CPError m => m a

You've got an existential type here. (Was that the intent?) The more common syntax for this purpose uses 'data' rather than 'type', and uses an explicit 'forall'. data CPResult a = forall m. MonadError CPError m => CPResult (m a) Hugs accepts this. (Though in the extended example I attempted, GHC mangaged the type inference while Hugs objected.)