[Haskell-cafe] Convert Data.Vector.Unboxed.Mutable.MVector to Data.Vector.Unboxed.Vector

[Amos Robinson]

Mutable is the type family from Vector to MVector. So the result type will
be an instance of Vector, but the input MVector doesn't need to be.
It's a little confusing that freeze is in Data.Unboxed.Vector, not
.Mutable:
https://hackage.haskell.org/package/vector-0.12.0.1/docs/Data-Vector-Unboxed.html#v:freeze

On Sun, 6 Aug 2017 at 12:59 Cody Goodman <codygman.consulting at gmail.com>
wrote:

> I see the type is:
>
> freeze :: (PrimMonad
> <https://hackage.haskell.org/package/primitive-0.6.2.0/docs/Control-Monad-Primitive.html#t:PrimMonad>
> m, Vector
> <https://hackage.haskell.org/package/vector-0.12.0.1/docs/Data-Vector-Generic.html#t:Vector>
> v a) => Mutable
> <https://hackage.haskell.org/package/vector-0.12.0.1/docs/Data-Vector-Generic.html#t:Mutable>
> v (PrimState
> <https://hackage.haskell.org/package/primitive-0.6.2.0/docs/Control-Monad-Primitive.html#t:PrimState>
> m) a -> m (v a)
>
>
> So there is a Vector constrant that MVector will not have. Does the
> Mutable type family get around this somehow?
>
>
> There doesn't seem to be a freeze function specifically for
> Data.Vector.Unboxed.Mutable.MVector listed at:
> https://hackage.haskell.org/package/vector-0.12.0.1/docs/Data-Vector-Unboxed-Mutable.html
>
> Thanks,
>
> Cody
>
> On Sat, Aug 5, 2017 at 9:56 PM, Amos Robinson <amos.robinson at gmail.com>
> wrote:
>
>> I think you want "Data.Vector.Generic.freeze", or unsafeFreeze if you are
>> sure you won't modify the mutable vector after making it immutable.
>>
>> https://hackage.haskell.org/package/vector-0.12.0.1/docs/Data-Vector-Generic.html#v:freeze
>>
>> On Sun, 6 Aug 2017 at 12:46 Cody Goodman <codygman.consulting at gmail.com>
>> wrote:
>>
>>> I want to do this so I can use the Data.Vector.Unboxed.Generic functions
>>> requiring the Vector constraint, namely the maxIndex function. Implementing
>>> maxIndex for Data.Vector.Unboxed.Mutable.MVector would be useful as well,
>>> but I'm even more confused at how to do that or where to begin.
>>>
>>> Here is some stubbed out code demonstrating this.
>>>
>>> {-# Language ScopedTypeVariables #-}
>>> module Main where
>>>
>>> import Control.Monad.Primitive
>>> import qualified Data.Vector.Unboxed
>>> import qualified Data.Vector.Generic as VG
>>> import qualified Data.Vector.Unboxed.Mutable as VM
>>> import qualified Data.Vector.Unboxed as V
>>>
>>> toImmutable :: VM.MVector RealWorld Int -> V.Vector Int
>>> toImmutable = undefined
>>>
>>> main :: IO ()
>>> main = do
>>>   v :: VM.MVector RealWorld Int <- VM.new 1
>>>   VM.write v 0 (3 :: Int)
>>>   x <- VM.read v 0
>>>   -- y <- VG.head . toImmutable $ v
>>>   -- print y
>>>   print $ VM.length v
>>>
>>> {-
>>> Thanks,
>>>
>>>
>>> Cody
>>> -}
>>> _______________________________________________
>>> Haskell-Cafe mailing list
>>> To (un)subscribe, modify options or view archives go to:
>>> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe
>>> Only members subscribed via the mailman list are allowed to post.
>>
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.haskell.org/pipermail/haskell-cafe/attachments/20170806/e0252c10/attachment.html>