add System.Posix.Types to default nhc98 build

[haskell-directory.git] / Data / Bits.hs

diff --git a/Data/Bits.hs b/Data/Bits.hs
index 25bc9a1..88f707a 100644 (file)
--- a/Data/Bits.hs
+++ b/Data/Bits.hs
@@ -1,4 +1,4 @@
-{-# OPTIONS -fno-implicit-prelude #-}
+{-# OPTIONS_GHC -fno-implicit-prelude #-}

 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Data.Bits
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Data.Bits

@@ -9,11 +9,11 @@
 -- Stability   :  experimental
 -- Portability :  portable
 --
 -- 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
---  "Data.Int" and "Data.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.

 --
 -----------------------------------------------------------------------------
 
 --
 -----------------------------------------------------------------------------
 

@@ -66,6 +66,10 @@ The 'Bits' class defines bitwise operations over integral types.
 
 * Bits are numbered from 0 with bit 0 being the least
   significant bit.
 
 * 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\"
 -}
 class Num a => Bits a where
     -- | Bitwise \"and\"

@@ -80,8 +84,11 @@ class Num a => Bits a where
     {-| Reverse all the bits in the argument -}
     complement        :: a -> a
 
     {-| 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
 
        An instance can define either this unified 'shift' or 'shiftL' and
        'shiftR', depending on which is more convenient for the type in

@@ -92,8 +99,8 @@ class Num a => Bits a where
                   | i==0 = x
                   | i>0  = x `shiftL` i
 
                   | 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.

 
         For unbounded types like 'Integer', 'rotate' is equivalent to 'shift'.
 
 
         For unbounded types like 'Integer', 'rotate' is equivalent to 'shift'.
 

@@ -160,8 +167,11 @@ class Num a => Bits a where
     shiftL            :: a -> Int -> a
     x `shiftL`  i = x `shift`  i
 
     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).
        (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
 
        An instance can define either this and 'shiftL' or the unified
        'shift', depending on which is more convenient for the type in

@@ -188,6 +198,8 @@ class Num a => Bits a where
     x `rotateR` i = x `rotate` (-i)
 
 instance Bits Int where
     x `rotateR` i = x `rotate` (-i)
 
 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#))
 #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#))

@@ -197,8 +209,8 @@ instance Bits Int where
         | i# >=# 0#        = I# (x# `iShiftL#` i#)
         | otherwise        = I# (x# `iShiftRA#` negateInt# i#)
     (I# x#) `rotate` (I# 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#))
         where
         x'# = int2Word# x#
         i'# = word2Int# (int2Word# i# `and#` int2Word# (wsib -# 1#))