Re: [Haskell-cafe] Implicit newtype unwrapping

Ah, that's a really good point. It seems then that there is a use for implicitly unwrapped newtypes, but perhaps only when you never really wanted to use a newtype to begin with but had to in order to use a different instance declaration for the same type. That suggests that the feature we'd really like is a way to declare that we want a type in a context to act as if it had a different instance declaration for a given typeclass, without having to go through newtype. Cheers, Greg On Dec 2, 2009, at 5:08 PM, Greg Fitzgerald wrote:

Gregory Crosswhite wrote:

...

Out of curiosity, why would one want a "newtype" that were unwrapped implicitly, rather than just using "type"?

One reason might be because you only switched from 'type' to 'newtype' so that you could write more refined Arbitrary instances for your QuickCheck tests.

-Greg