[Haskell-cafe] Looking for largest power of 2 <= Integer

[Don Stewart]

dbenbenn:
> On Dec 4, 2007 11:51 AM, Don Stewart <dons at galois.com> wrote:
> > Awesome. We can use this in Data.Bits, if you've got some QuickChecks
> > for it.
> 
> Hear hear.  But is there any way to just make the compiler use
> fastTestBit in place of testBit :: (Bits a) => a -> Int -> Bool when a
> = Integer?  (That is, without having to introduce a new function to
> the public interface of Data.Bits.)  Some kind of SPECIALIZE pragma,
> perhaps?

{-# RULES
    "Integer fastTestBit" forall x n.
    testBit x n = fastTestBit :: Integer -> Int -> Bool
 #-}

I think should work. If testBit is in the Bits class though, we can just
add it for instance Bits Integer

-- Don