[Haskell-cafe] getPtrSize works, but is annoying

2009-12-18 Thread Gregory Crosswhite 
Ugh, I figured out how to write code to do what I wanted, but it seems like an 
ugly solution:

getPtrSize :: Ptr a - Int
getPtrSize = getFrom dummy
  where
getFrom :: a - Ptr a - Int
getFrom dummy _ = sizeOf dummy

Any thoughts on a less ugly solution, or is this really the best that I can do?

Cheers,
Greg

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Re: [Haskell-cafe] getPtrSize works, but is annoying

2009-12-18 Thread Luke Palmer 
On Fri, Dec 18, 2009 at 12:20 PM, Gregory Crosswhite
gcr...@phys.washington.edu wrote:
 Ugh, I figured out how to write code to do what I wanted, but it seems like 
 an ugly solution:

        getPtrSize :: Ptr a - Int
        getPtrSize = getFrom dummy
          where
                getFrom :: a - Ptr a - Int
                getFrom dummy _ = sizeOf dummy

With -XScopedTypeVariables:

getPtrSize :: forall a. Ptr a - Int
getPtrSize p = sizeOf (undefined :: a)
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