Add instance Storable Ordering

[David Feuer]

But shouldn't Ordering have the alignment and size of Int8 rather than that
of Int? At least in principle?

On Tue, Oct 8, 2019, 11:38 AM David Feuer <david.feuer at gmail.com> wrote:

> 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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>
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