Re: [Haskell] for large x, log (x::Integer) :: Double

Dylan Thurston:

For those who aren't aware: working with logs base 2 internally will be very much faster than logs base 10, since the numbers are stored internally in a base-2 representation. (Note that 'show' converts to base 10, which involves a large number of divisions in the easy algorithm.)

Does Haskell provide any means of determining the number of binary digits in an Integer other than by repeated division? In the absence of an appropriate built-in or library function it may be that the fastest way is to use (length (show x)), multiply by some fiddle factor, add some fiddle term to get n, then check whether x < 2 ** n. Could "log2 :: Integer -> Integer" be added to some wish list?