fix shift docs to match ffi spec

diff --git a/Data/Bits.hs b/Data/Bits.hs
index 4564bce..88f707a 100644 (file)
--- a/Data/Bits.hs
+++ b/Data/Bits.hs
@@ -84,8 +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

@@ -96,8 +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'.
 

@@ -164,8 +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