Coercible class (Was: newtype wrappers)

Richard Eisenberg eir at
Sun Sep 15 20:48:16 UTC 2013

Very cool!

In the feature as pushed, is it possible to use coerce on any old newtype? If so, then it really is a language feature and probably should go into the manual, if `coerce` is exposed.

What was the end result of the discussion on abstraction? Can a library control how its types are coerced?


On Sep 13, 2013, at 6:13 PM, Joachim Breitner <mail at> wrote:

> Hi,
> Am Montag, den 09.09.2013, 11:26 -0500 schrieb Austin Seipp:
>> It sounds like Simon thinks your work is good to go, so when your tree
>> is clean, feel free to push.
> done!
> Given that in the final form the feature, to the user, looks like a
> library and not a language extension, I decided to put the documentation
> not in the users guide, but only in the haddock for coerce and
> Coercible.
> So far they only live in GHC.Prim. Should we expose them in GHC.Prim for
> 7.8, or only in 7.10?
> Greetings,
> Joachim
> -- 
> Joachim “nomeata” Breitner
>  mail at joachim-breitner.de
>  Jabber: nomeata at  • GPG-Key: 0x4743206C
>  Debian Developer: nomeata at
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