Improved interface to UArray

[Carter Schonwald]

looking at current base,
https://downloads.haskell.org/ghc/latest/docs/html/libraries/base-4.13.0.0/GHC-Arr.html
it seems (naively to me) that nothing precludes the array package from
using PrimMonad m => for the IO etc monad instances,
with zero impact on the interface as defined in base. Or am I missing
something?

On Tue, Mar 3, 2020 at 6:39 PM Carter Schonwald <carter.schonwald at gmail.com>
wrote:

> I meant specifically using PrimMonad, rather than the prim array
> facilities, to write the instances
>
> On Tue, Mar 3, 2020 at 5:14 PM Zemyla <zemyla at gmail.com> wrote:
>
>> Because a lot of the stuff is defined in GHC.Arr, in base. Also, the Prim
>> instance for Bool is different than the UArray instance for Bool.
>>
>> On Tue, Mar 3, 2020, 14:56 chessai . <chessai1996 at gmail.com> wrote:
>>
>>> Zemlya, could you expound on why you think a primitive dependency is a
>>> bad idea? I'm just not sure what reasons you have in mind.
>>>
>>> Thanks
>>>
>>> On Tue, Mar 3, 2020, 12:31 PM Zemyla <zemyla at gmail.com> wrote:
>>>
>>>> We should probably use something similar, but I don't think a
>>>> dependency on primitive is a good idea.
>>>>
>>>> On Tue, Mar 3, 2020, 14:28 Carter Schonwald <carter.schonwald at gmail.com>
>>>> wrote:
>>>>
>>>>> Hey Zemyla!
>>>>> one fuzzy question i have, and perhaps you have a perspective on this,
>>>>> would/could the PrimMonad machinery in primitive help simplify / clean up
>>>>> stuff here too?
>>>>>
>>>>> On Mon, Feb 24, 2020 at 9:46 AM Zemyla <zemyla at gmail.com> wrote:
>>>>>
>>>>>> It's currently hard to describe that a type should be usable with
>>>>>> UArray or IOUArray, and almost impossible to describe without
>>>>>> QualifiedConstraints that it should be usable with STUArray. And it's
>>>>>> actually impossible to use GeneralizedNewtypeDeriving to derive new
>>>>>> instances of IArray or MArray. It also means that it's difficult to keep
>>>>>> the three sets of instances in sync.
>>>>>>
>>>>>> Therefore, there should be (taking inspiration from primitive) a
>>>>>> class that describes types which can be used in unboxed arrays. It'd be
>>>>>> something along the lines of:
>>>>>>
>>>>>> class Unboxed e where
>>>>>>   unsafeNewUArray :: Int# -> e -> State# s -> (# State# s,
>>>>>> MutableByteArray# s #)
>>>>>>   unsafeNewUArray_ :: Const (Int# -> State# s -> (# State# s,
>>>>>> MutableByteArray# s #)) e
>>>>>>   unsafeReadUArray :: MutableByteArray# s -> Int# -> State# s -> (#
>>>>>> State# s, e #)
>>>>>>   unsafeWriteUArray :: MutableByteArray# s -> Int# -> e -> State# s
>>>>>> -> State# s
>>>>>>   unsafeIndexUArray :: ByteArray# -> Int# -> e
>>>>>>
>>>>>> And then the instances for UArray, STUArray, and IOUArray would be:
>>>>>>
>>>>>> instance Unboxed e => IArray UArray e where ...
>>>>>> instance Unboxed e => MArray IOUArray e IO where ...
>>>>>> instance Unboxed e => MArray (STUArray s) e (ST s) where ...
>>>>>>
>>>>>> Incidentally, this also means it'd be less effort to add instances
>>>>>> like Unboxed CInt, Unboxed a => Unboxed (Complex a), and Unboxed Ordering.
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