-{-# OPTIONS -fno-implicit-prelude #-}
+{-# OPTIONS_GHC -fno-implicit-prelude #-}
-----------------------------------------------------------------------------
-- |
-- Module : Data.Bits
-- Stability : experimental
-- Portability : portable
--
--- This module defines bitwise operations for signed and unsigned
--- integers. Instances of the class 'Bits' for the 'Int' and
--- 'Integer' types are available from this module, and instances for
--- explicitly sized integral types are available from the
--- "Int" and "Word" modules.
+-- This module defines bitwise operations for signed and unsigned
+-- integers. Instances of the class 'Bits' for the 'Int' and
+-- 'Integer' types are available from this module, and instances for
+-- explicitly sized integral types are available from the
+-- "Data.Int" and "Data.Word" modules.
--
-----------------------------------------------------------------------------
-- See library document for details on the semantics of the
-- individual operations.
-#ifdef __GLASGOW_HASKELL__
+#if defined(__GLASGOW_HASKELL__) || defined(__HUGS__)
#include "MachDeps.h"
+#endif
+
+#ifdef __GLASGOW_HASKELL__
import GHC.Num
import GHC.Real
import GHC.Base
#endif
+#ifdef __HUGS__
+import Hugs.Bits
+#endif
+
infixl 8 `shift`, `rotate`, `shiftL`, `shiftR`, `rotateL`, `rotateR`
infixl 7 .&.
infixl 6 `xor`
* Bits are numbered from 0 with bit 0 being the least
significant bit.
+
+Minimal complete definition: '.&.', '.|.', 'xor', 'complement',
+('shift' or ('shiftL' and 'shiftR')), ('rotate' or ('rotateL' and 'rotateR')),
+'bitSize' and 'isSigned'.
-}
class Num a => Bits a where
-- | Bitwise \"and\"
{-| Reverse all the bits in the argument -}
complement :: a -> a
- {-| Shift the argument left by the specified number of bits.
- Right shifts (signed) are specified by giving a negative value.
+ {-| @'shift' x i@ shifts @x@ left by @i@ bits if @i@ is positive,
+ or right by @-i@ bits otherwise.
+ Right shifts perform sign extension on signed number types;
+ i.e. they fill the top bits with 1 if the @x@ is negative
+ and with 0 otherwise.
An instance can define either this unified 'shift' or 'shiftL' and
'shiftR', depending on which is more convenient for the type in
| i==0 = x
| i>0 = x `shiftL` i
- {-| Rotate the argument left by the specified number of bits.
- Right rotates are specified by giving a negative value.
+ {-| @'rotate' x i@ rotates @x@ left by @i@ bits if @i@ is positive,
+ or right by @-i@ bits otherwise.
- 'rotate' is well defined only if 'bitSize' is also well defined
- ('bitSize' is undefined for 'Integer', for example).
+ For unbounded types like 'Integer', 'rotate' is equivalent to 'shift'.
An instance can define either this unified 'rotate' or 'rotateL' and
'rotateR', depending on which is more convenient for the type in
testBit :: a -> Int -> Bool
{-| Return the number of bits in the type of the argument. The actual
- value of the argument is ignored -}
+ value of the argument is ignored. The function 'bitSize' is
+ undefined for types that do not have a fixed bitsize, like 'Integer'.
+ -}
bitSize :: a -> Int
{-| Return 'True' if the argument is a signed type. The actual
shiftL :: a -> Int -> a
x `shiftL` i = x `shift` i
- {-| Shift the argument right (signed) by the specified number of bits
+ {-| Shift the first argument right by the specified number of bits
(which must be non-negative).
+ Right shifts perform sign extension on signed number types;
+ i.e. they fill the top bits with 1 if the @x@ is negative
+ and with 0 otherwise.
An instance can define either this and 'shiftL' or the unified
'shift', depending on which is more convenient for the type in
rotateR :: a -> Int -> a
x `rotateR` i = x `rotate` (-i)
-#ifdef __GLASGOW_HASKELL__
instance Bits Int where
+ {-# INLINE shift #-}
+
+#ifdef __GLASGOW_HASKELL__
(I# x#) .&. (I# y#) = I# (word2Int# (int2Word# x# `and#` int2Word# y#))
(I# x#) .|. (I# y#) = I# (word2Int# (int2Word# x# `or#` int2Word# y#))
(I# x#) `xor` (I# y#) = I# (word2Int# (int2Word# x# `xor#` int2Word# y#))
complement (I# x#) = I# (word2Int# (int2Word# x# `xor#` int2Word# (-1#)))
(I# x#) `shift` (I# i#)
- | i# >=# 0# = I# (x# `iShiftL#` i#)
- | otherwise = I# (x# `iShiftRA#` negateInt# i#)
+ | i# >=# 0# = I# (x# `iShiftL#` i#)
+ | otherwise = I# (x# `iShiftRA#` negateInt# i#)
(I# x#) `rotate` (I# i#) =
- I# (word2Int# ((x'# `shiftL#` i'#) `or#`
- (x'# `shiftRL#` (wsib -# i'#))))
+ 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 (??) -}
- bitSize _ = WORD_SIZE_IN_BITS
- isSigned _ = True
+ bitSize _ = WORD_SIZE_IN_BITS
+#else /* !__GLASGOW_HASKELL__ */
+
+#ifdef __HUGS__
+ (.&.) = primAndInt
+ (.|.) = primOrInt
+ xor = primXorInt
+ complement = primComplementInt
+ shift = primShiftInt
+ bit = primBitInt
+ testBit = primTestInt
+ bitSize _ = SIZEOF_HSINT*8
+#elif defined(__NHC__)
+ (.&.) = nhc_primIntAnd
+ (.|.) = nhc_primIntOr
+ xor = nhc_primIntXor
+ complement = nhc_primIntCompl
+ shiftL = nhc_primIntLsh
+ shiftR = nhc_primIntRsh
+ bitSize _ = 32
+#endif /* __NHC__ */
+
+ x `rotate` i
+ | i<0 && x<0 = let left = i+bitSize x in
+ ((x `shift` i) .&. complement ((-1) `shift` left))
+ .|. (x `shift` left)
+ | i<0 = (x `shift` i) .|. (x `shift` (i+bitSize x))
+ | i==0 = x
+ | i>0 = (x `shift` i) .|. (x `shift` (i-bitSize x))
+
+#endif /* !__GLASGOW_HASKELL__ */
+
+ isSigned _ = True
+
+#ifdef __NHC__
+foreign import ccall nhc_primIntAnd :: Int -> Int -> Int
+foreign import ccall nhc_primIntOr :: Int -> Int -> Int
+foreign import ccall nhc_primIntXor :: Int -> Int -> Int
+foreign import ccall nhc_primIntLsh :: Int -> Int -> Int
+foreign import ccall nhc_primIntRsh :: Int -> Int -> Int
+foreign import ccall nhc_primIntCompl :: Int -> Int
+#endif /* __NHC__ */
instance Bits Integer where
+#ifdef __GLASGOW_HASKELL__
(S# x) .&. (S# y) = S# (word2Int# (int2Word# x `and#` int2Word# y))
x@(S# _) .&. y = toBig x .&. y
x .&. y@(S# _) = x .&. toBig y
complement (S# x) = S# (word2Int# (int2Word# x `xor#` int2Word# (0# -# 1#)))
complement (J# s d) = case complementInteger# s d of (# s, d #) -> J# s d
+#else
+ -- reduce bitwise binary operations to special cases we can handle
+
+ x .&. y | x<0 && y<0 = complement (complement x `posOr` complement y)
+ | otherwise = x `posAnd` y
+
+ x .|. y | x<0 || y<0 = complement (complement x `posAnd` complement y)
+ | otherwise = x `posOr` y
+
+ x `xor` y | x<0 && y<0 = complement x `posXOr` complement y
+ | x<0 = complement (complement x `posXOr` y)
+ | y<0 = complement (x `posXOr` complement y)
+ | otherwise = x `posXOr` y
+
+ -- assuming infinite 2's-complement arithmetic
+ complement a = -1 - a
+#endif
shift x i | i >= 0 = x * 2^i
| otherwise = x `div` 2^(-i)
rotate x i = shift x i -- since an Integer never wraps around
- bitSize _ = error "Bits.bitSize(Integer)"
+ bitSize _ = error "Data.Bits.bitSize(Integer)"
isSigned _ = True
-#endif
-
-#ifdef __NHC__
-instance Bits Int where
- (.&.) = nhc_primIntAnd
- (.|.) = nhc_primIntOr
- xor = nhc_primIntXor
- complement = nhc_primIntCompl
- shiftL = nhc_primIntLsh
- shiftR = nhc_primIntRsh
- bitSize _ = 32
- isSigned _ = True
-
-foreign import ccall nhc_primIntAnd :: Int -> Int -> Int
-foreign import ccall nhc_primIntOr :: Int -> Int -> Int
-foreign import ccall nhc_primIntXor :: Int -> Int -> Int
-foreign import ccall nhc_primIntLsh :: Int -> Int -> Int
-foreign import ccall nhc_primIntRsh :: Int -> Int -> Int
-foreign import ccall nhc_primIntCompl :: Int -> Int
-
-instance Bits Integer where
- -- (.&.) a b = undefined
- -- (.|.) a b = undefined
- -- xor a b = undefined
- complement a = (-a)
- x `shift` i | i<0 = x `div` (2^(-i))
- | i==0 = x
- | i>0 = x * (2^i)
- x `rotate` i = x `shift` i -- an Integer never wraps
- bitSize _ = error "Data.Bits: bitSize :: Integer -> Int"
- isSigned _ = True
-
-#endif
+#ifndef __GLASGOW_HASKELL__
+-- Crude implementation of bitwise operations on Integers: convert them
+-- to finite lists of Ints (least significant first), zip and convert
+-- back again.
+
+-- posAnd requires at least one argument non-negative
+-- posOr and posXOr require both arguments non-negative
+
+posAnd, posOr, posXOr :: Integer -> Integer -> Integer
+posAnd x y = fromInts $ zipWith (.&.) (toInts x) (toInts y)
+posOr x y = fromInts $ longZipWith (.|.) (toInts x) (toInts y)
+posXOr x y = fromInts $ longZipWith xor (toInts x) (toInts y)
+
+longZipWith :: (a -> a -> a) -> [a] -> [a] -> [a]
+longZipWith f xs [] = xs
+longZipWith f [] ys = ys
+longZipWith f (x:xs) (y:ys) = f x y:longZipWith f xs ys
+
+toInts :: Integer -> [Int]
+toInts n
+ | n == 0 = []
+ | otherwise = mkInt (n `mod` numInts):toInts (n `div` numInts)
+ where mkInt n | n > toInteger(maxBound::Int) = fromInteger (n-numInts)
+ | otherwise = fromInteger n
+
+fromInts :: [Int] -> Integer
+fromInts = foldr catInt 0
+ where catInt d n = (if d<0 then n+1 else n)*numInts + toInteger d
+
+numInts = toInteger (maxBound::Int) - toInteger (minBound::Int) + 1
+#endif /* !__GLASGOW_HASKELL__ */
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