Re: [Haskell-cafe] MonadLib usage

On Sun, Jul 18, 2010 at 5:59 PM, Emil Melnikov wrote:

On 2010, July 18, 23:27 Ivan Lazar Miljenovic wrote:

...

When discussing a similar issue with Manuel Chakravarty, he convinced me that cunning newtype deriving is actually rather bad in practice and shouldn't be used as there's a lack of proofs or some such (I can't remember the arguments, but I remember being convinced by them :p).

Hmm...  I can't imagine how it is possible, since new and original types are isomorphic.

Can you give me some pointers to this discussion (links or keywords)?

They are isomorphic, but distinct. This trac ticket is relevant: http://hackage.haskell.org/trac/ghc/ticket/1496