Proposal: bring BBP to Arrays

[David Feuer]

GHC.Arr defines

{-# INLINE unsafeArray' #-}
unsafeArray' :: Ix i => (i,i) -> Int -> [(Int, e)] -> Array i e
unsafeArray' (l,u) n@(I# n#) ies = runST (ST $ \s1# ->
    case newArray# n# arrEleBottom s1# of
        (# s2#, marr# #) ->
            foldr (fill marr#) (done l u n marr#) ies s2#)


This is a critical array-building function, but it only works for lists.
I'd like to change that. The two things that would have to change would be
the type signature, which would become

unsafeArray' :: (Foldable f, Ix i) => (i,i) -> Int -> f (Int, e) -> Array i
e

and its choice of foldr, from GHC.List.foldr to Data.Foldable.foldr.

On Thu, Nov 13, 2014 at 4:22 AM, Bob Ippolito <bob at redivi.com> wrote:

>
>
> On Thu, Nov 13, 2014 at 1:17 AM, Henning Thielemann <
> lemming at henning-thielemann.de> wrote:
>
>>
>>
>> On Wed, 12 Nov 2014, David Feuer wrote:
>>
>>  It looks like Array and IArray have missed some important BBP bits.
>>>
>>
>> What is BBP?
>>
>
> From https://ghc.haskell.org/trac/ghc/wiki/Status/Oct14 -
>
> BBP: Foldable/Traversable. As part of the so-called "Burning-Bridges
> Proposal", the monomorphic definitions in Prelude/Data.List/Control.Monad
> that conflict with those from Data.Foldable and Data.Traversable have been
> replaced by their respective ones from Data.Foldable/Data.Traversable. This
> will be in 7.10
>
>
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