Indeed, it worked (thanks again!):
{-# 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
main :: IO ()
main = do
v :: VM.MVector RealWorld Int <- VM.new 1
VM.write v 0 (3 :: Int)
x <- VM.read v 0
v' <- V.freeze v
print $ VG.head v'
print $ VM.length v
On Sat, Aug 5, 2017 at 10:54 PM, Cody Goodman wrote: Thanks! I'll try it out in a bit. On Aug 5, 2017 10:32 PM, "Amos Robinson" Yes, I believe Data.Vector.Generic.freeze will work. But I would use the
one from Data.Vector.Unboxed unless you really need the generic version.
Sometimes the extra constraints in the generic version can be a bit
cumbersome, requiring extra type annotations where the specific versions
don't. On Sun, 6 Aug 2017 at 13:22 Cody Goodman I'm not back at a computer yet, but so I and others reading these
archives in the future know: Does that mean that freeze from
Data.Vector.Generic.freeze should work for me then? On Sat, Aug 5, 2017 at 10:05 PM, 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 I see the type is: freeze :: (PrimMonad
https://hackage.haskell.org/package/primitive-0.6.2.0/docs/Control-Monad-Pri...
m, Vector
https://hackage.haskell.org/package/vector-0.12.0.1/docs/Data-Vector-Generic...
v a) => Mutable
https://hackage.haskell.org/package/vector-0.12.0.1/docs/Data-Vector-Generic...
v (PrimState
https://hackage.haskell.org/package/primitive-0.6.2.0/docs/Control-Monad-Pri...
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/Dat
a-Vector-Unboxed-Mutable.html Thanks, Cody On Sat, Aug 5, 2017 at 9:56 PM, Amos Robinson 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/Dat
a-Vector-Generic.html#v:freeze On Sun, 6 Aug 2017 at 12:46 Cody Goodman <
codygman.consulting@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.