1  
 2  {-# LANGUAGE Strict #-}
 3  module Misc where
 4  
 5  --------------------------------------------------------------------------------
 6  
 7  import Data.Bits
 8  
 9  --------------------------------------------------------------------------------
10  
11  class ShowHex a where
12    showHex  :: a -> String
13  
14  printHex :: ShowHex a => a -> IO ()
15  printHex x = putStrLn (showHex x)
16  
17  --------------------------------------------------------------------------------
18  -- Integer logarithm
19  
20  -- | Largest integer @k@ such that @2^k@ is smaller or equal to @n@
21  integerLog2 :: Integer -> Int
22  integerLog2 n = go n where
23    go 0 = -1
24    go k = 1 + go (shiftR k 1)
25  
26  -- | Smallest integer @k@ such that @2^k@ is larger or equal to @n@
27  ceilingLog2 :: Integer -> Int
28  ceilingLog2 0 = 0
29  ceilingLog2 n = 1 + go (n-1) where
30    go 0 = -1
31    go k = 1 + go (shiftR k 1)
32    
33  --------------------------------------------------------------------------------