Void type in base

[Dan Doel]

Are GHC's newtype coercions going to know that the second step of 'f Void
-> f (forall a. a) -> forall a. f a' is valid due to f being a Functor? I'm
not sure that can be counted upon.



On Thu, Jul 18, 2013 at 1:33 PM, Edward Kmett <ekmett at gmail.com> wrote:

> You can get there if you use
>
> newtype Void = Void { absurd :: forall a. a }
>
> instead.
>
> -Edward
>
> On Wed, Jul 17, 2013 at 6:03 PM, Joachim Breitner <
> mail at joachim-breitner.de> wrote:
>
>> Hi,
>>
>> Am Mittwoch, den 17.07.2013, 15:27 -0400 schrieb Edward Kmett:
>> > Now the Data.Void.Unsafe module provides that functionality (as
>> > unsafeVacuous) and vacuous itself is provided for compatibility with
>> > code that used it, and is left in case we ever get something in
>> > Functor that lets us apply newtype coercions directly to the Functor's
>> > parameter.
>>
>> how would lifting newtype coercions to functors help here:
>>   vacuous :: Functor f => f Void -> f a
>> Void is not a newtype of a.
>>
>> Greetings,
>> Joachim
>>
>>
>> --
>> Joachim “nomeata” Breitner
>>   mail at joachim-breitner.de • http://www.joachim-breitner.de/
>>   Jabber: nomeata at joachim-breitner.de  • GPG-Key: 0x4743206C
>>   Debian Developer: nomeata at debian.org
>>
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>
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