Dan Piponi wrote: > Is there anything in any of the interfaces to Integer that will allow > me to quickly find the highest bit set in an Integer? If not, does > anyone have any recommendations for how to do it efficiently. There > are some obvious things that come to mind but which might involve > quite a bit of useless copying of data internally by the > implementation of Integer. > -- > Dan The subject line and your description disagree by 1 bit. Take the number 7: its binary representation would be 0111, with 0100 being the highest bit, whereas the smallest power of 2 >= 7 is 8, or 1000 in binary. And how do you want the results? The place value of that highest bit? Or its index?
For the index, how about this: truncate . (/(log 2)) . log . fromIntegral for the place value, just add an exponent function and another cast: (2**) . fromIntegral . truncate . (/(log 2)) . log . fromIntegral If you want the smallest power of 2 >= the integer, just change truncate to ceiling. _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
