Re: [Haskell-cafe] Synthetic values?

On 09.02.2011 23:16, Cristiano Paris wrote:

On Wed, Feb 9, 2011 at 19:33, Alexey Khudyakov wrote:

...

... If Private is not exported one cannot add instances to PRead.

Nice trick. I would have thought of hiding the classes PRead and PWrite but I'm not sure if it could break the code.

It shouldn't but it would be impossible to write signatures for polymorphic functions which use thoose type classes. foo :: PWrite p => Sealed p Int <-- impossible to write foo = ...