Re: [Haskell-cafe] ANN: exists-0.1

On 02/07/2012 04:05 PM, Gábor Lehel wrote:

On Tue, Feb 7, 2012 at 7:23 AM, Mikhail Vorozhtsov wrote:

...

Even better, you can write

type ExistentialWith c e = (Existential e, c ~ ConstraintOf e)

instead of

class (Existential e, c ~ ConstraintOf e) => ExistentialWith c e instance (Existential e, c ~ ConstraintOf e) => ExistentialWith c e

and drop UndecidableInstances.

I actually mentioned this in the preceding point of the [snip]. The problem is that it's not even better because you can't partially apply it. Ah, sorry, I got sloppy. Have you encountered situations where partial application of such "constraint aliases" becomes a problem?