On Fri, 25 Dec 2009, Lennart Augustsson wrote:

sizeOfPtr :: Ptr a -> Int sizeOfPtr = sizeOf . (undefined :: Ptr a -> a)

No need for scoped type variables. But it does assume sizeOf does not use its argument.

That's even better. I'll add that to the Wiki.  http://www.haskell.org/haskellwiki/Scoped_type_variables#Avoiding_Scoped_Typ...