Add instance Storable Ordering

[David Feuer]

newtype WrappedEnum a = WrappedEnum a

instance Enum a => Storable (WrappedEnum a) where
  ...

deriving via (WrappedEnum Ordering)
  instance Storable Ordering

On Tue, Oct 8, 2019, 11:34 AM Sven Panne <svenpanne at gmail.com> wrote:

> Am Di., 8. Okt. 2019 um 16:57 Uhr schrieb Simon Jakobi via Libraries <
> libraries at haskell.org>:
>
>> That seems like a good idea! [...]
>>
>
> Looks OK, but let's use toEnum in peekElemOff:
>
>   instance Storable Ordering where
>     sizeOf _ = sizeOf (undefined :: CInt)
>     alignment _ = alignment (undefined :: CInt)
>     peekElemOff p i = toEnum . fromIntegral <$> peekElemOff (castPtr p ::
> Ptr CInt) i
>     pokeElemOff p i = pokeElemOff (castPtr p :: Ptr CInt) i . fromIntegral
> . fromEnum
>
> This is more symmetrical with pokeElemOff and less obfuscated. Note that
> the instance works for every Enum, so if there are more cases like
> Ordering, it might be worth to abstract that out.
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