-{-# OPTIONS_GHC -XNoImplicitPrelude #-}
+{-# LANGUAGE CPP, NoImplicitPrelude, BangPatterns, MagicHash #-}
+
-----------------------------------------------------------------------------
-- |
-- Module : Data.Bits
#ifdef __GLASGOW_HASKELL__
import GHC.Num
-import GHC.Real
import GHC.Base
#endif
question. -}
shift :: a -> Int -> a
- x `shift` i | i<0 = x `shiftR` (-i)
- | i==0 = x
- | i>0 = x `shiftL` i
+ x `shift` i | i<0 = x `shiftR` (-i)
+ | i>0 = x `shiftL` i
+ | otherwise = x
{-| @'rotate' x i@ rotates @x@ left by @i@ bits if @i@ is positive,
or right by @-i@ bits otherwise.
question. -}
rotate :: a -> Int -> a
- x `rotate` i | i<0 = x `rotateR` (-i)
- | i==0 = x
- | i>0 = x `rotateL` i
+ x `rotate` i | i<0 = x `rotateR` (-i)
+ | i>0 = x `rotateL` i
+ | otherwise = x
{-
-- Rotation can be implemented in terms of two shifts, but care is
| i>0 = (x `shift` i) .|. (x `shift` (i-bitSize x))
-}
- -- | @bit i@ is a value with the @i@th bit set
+ -- | @bit i@ is a value with the @i@th bit set and all other bits clear
bit :: Int -> a
-- | @x \`setBit\` i@ is the same as @x .|. bit i@
value of the argument is ignored -}
isSigned :: a -> Bool
+ {-# INLINE bit #-}
+ {-# INLINE setBit #-}
+ {-# INLINE clearBit #-}
+ {-# INLINE complementBit #-}
+ {-# INLINE testBit #-}
bit i = 1 `shiftL` i
x `setBit` i = x .|. bit i
x `clearBit` i = x .&. complement (bit i)
'shift', depending on which is more convenient for the type in
question. -}
shiftL :: a -> Int -> a
+ {-# INLINE shiftL #-}
x `shiftL` i = x `shift` i
{-| Shift the first argument right by the specified number of bits
'shift', depending on which is more convenient for the type in
question. -}
shiftR :: a -> Int -> a
+ {-# INLINE shiftR #-}
x `shiftR` i = x `shift` (-i)
{-| Rotate the argument left by the specified number of bits
'rotate', depending on which is more convenient for the type in
question. -}
rotateL :: a -> Int -> a
+ {-# INLINE rotateL #-}
x `rotateL` i = x `rotate` i
{-| Rotate the argument right by the specified number of bits
'rotate', depending on which is more convenient for the type in
question. -}
rotateR :: a -> Int -> a
+ {-# INLINE rotateR #-}
x `rotateR` i = x `rotate` (-i)
instance Bits Int where
I# (word2Int# ((x'# `uncheckedShiftL#` i'#) `or#`
(x'# `uncheckedShiftRL#` (wsib -# i'#))))
where
- x'# = int2Word# x#
- i'# = word2Int# (int2Word# i# `and#` int2Word# (wsib -# 1#))
- wsib = WORD_SIZE_IN_BITS# {- work around preprocessor problem (??) -}
+ !x'# = int2Word# x#
+ !i'# = word2Int# (int2Word# i# `and#` int2Word# (wsib -# 1#))
+ !wsib = WORD_SIZE_IN_BITS# {- work around preprocessor problem (??) -}
bitSize _ = WORD_SIZE_IN_BITS
- {-# INLINE shiftR #-}
- -- same as the default definition, but we want it inlined (#2376)
- x `shiftR` i = x `shift` (-i)
#else /* !__GLASGOW_HASKELL__ */
#ifdef __HUGS__
(.|.) = orInteger
xor = xorInteger
complement = complementInteger
+ shift x i@(I# i#) | i >= 0 = shiftLInteger x i#
+ | otherwise = shiftRInteger x (negateInt# i#)
#else
-- reduce bitwise binary operations to special cases we can handle
-- assuming infinite 2's-complement arithmetic
complement a = -1 - a
-#endif
-
shift x i | i >= 0 = x * 2^i
| otherwise = x `div` 2^(-i)
+#endif
rotate x i = shift x i -- since an Integer never wraps around