Re: Proposal: Don't require users to use undefined

On Wed, Oct 27, 2010 at 8:09 AM, Isaac Dupree wrote:

On 10/27/10 01:51, Bas van Dijk wrote:

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On Tue, Oct 26, 2010 at 9:09 PM, Henning Thielemann  wrote:

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On Tue, 26 Oct 2010, Bas van Dijk wrote:

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malloc :: forall a. Storable a =>  IO (Ptr a) malloc = mallocBytes (untag (sizeOf :: SizeOf a))

(Note that this does require the ScopedTypeVariables language extension.)

Haskell 98 solution would be nicer. Something like

...

malloc :: Storable a =>  IO (Ptr a) malloc =

    let aux :: Storable a =>  SizeOf a ->  IO (Ptr a)         aux = mallocBytes . untag     in  aux sizeOf

Great! It's nice to know that this proposal doesn't require ScopedTypeVariables.

It may not *require* it, but the code using ScopedTypeVariables is far more readable than that Haskell98/Haskell2010 code (though, perhaps we can improve on its readability a bit).

Indeed. My patches for base and the other packages uses ScopedTypeVariables extensively. It makes code shorter and easier to read. Is using ScopedTypeVariables a problem by the way? Should base use Haskell2010 exclusively or are extensions allowed?

(ScopedTypeVariables is not in Haskell2010, according to http://www.haskell.org/onlinereport/haskell2010/haskellli2.html#x3-5000 )

I hope they will be in Haskell2011. Bas