{-# LANGUAGE UndecidableInstances #-} class OldConstraint a => NewtypedConstraint a instance OldConstraint a => NewtypedConstraint a perhaps? Nice thing is you don't even need to do wrapping/unwrapping, like you do with data newtypes. On Tue, Mar 12, 2013 at 2:18 PM, Roman Cheplyaka wrote:

Is there a way to newtype a constraint?

Imagine a type class parameterised over constraints. What do I do if I want multiple instances for (essentially) the same constraint?

Roman

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On 12 March 2013 13:18, Roman Cheplyaka wrote:

Is there a way to newtype a constraint?

Imagine a type class parameterised over constraints. What do I do if I want multiple instances for (essentially) the same constraint?

It would make sense to add support for this to newtype directly. I think it would also make sense to allow newtypes over types of kind #. "All" that is required is some implementation effort: I looked into doing this as part of the constraint kinds patches but it is a bit messy. Max