3. Bits

This library defines bitwise operations for signed and unsigned ints.

module Bits where
infixl 8 `shift`, `rotate`
infixl 7 .&.
infixl 6 `xor`
infixl 5 .|.

class Bits a where
  (.&.), (.|.), xor :: a -> a -> a
  complement        :: a -> a
  shift             :: a -> Int -> a
  rotate            :: a -> Int -> a
  bit               :: Int -> a        
  setBit            :: a -> Int -> a   
  clearBit          :: a -> Int -> a   
  complementBit     :: a -> Int -> a   
  testBit           :: a -> Int -> Bool
  bitSize           :: a -> Int
  isSigned          :: a -> Bool

shiftL, shiftR   :: Bits a => a -> Int -> a
rotateL, rotateR :: Bits a => a -> Int -> a
shiftL  a i = shift  a i
shiftR  a i = shift  a (-i)
rotateL a i = rotate a i
rotateR a i = rotate a (-i)

Notes:

• bitSize and isSigned are like floatRadix and floatDigits -- they return parameters of the type of their argument rather than of the particular argument they are applied to. bitSize returns the number of bits in the type; and isSigned returns whether the type is signed or not.
• shift performs sign extension on signed number types. That is, right shifts fill the top bits with 1 if the number is negative and with 0 otherwise.
• Bits are numbered from 0 with bit 0 being the least significant bit.
• shift x i and rotate x i shift to the left if i is positive and to the right otherwise.
• bit i is the value with the i'th bit set.