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<TITLE>The Hugs-GHC Extension Libraries: Bits </TITLE>
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<H2><A NAME="s4">4. Bits </A></H2>
<P>This library defines bitwise operations for signed and unsigned ints.</P>
<P>
<BLOCKQUOTE><CODE>
<PRE>
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)
</PRE>
</CODE></BLOCKQUOTE>
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<P>Notes:
<UL>
<LI><CODE>bitSize</CODE> and <CODE>isSigned</CODE> are like <CODE>floatRadix</CODE> and <CODE>floatDigits</CODE>
-- they return parameters of the <EM>type</EM> of their argument rather than
of the particular argument they are applied to. <CODE>bitSize</CODE> returns
the number of bits in the type (or <CODE>Nothing</CODE> for unbounded types); and
<CODE>isSigned</CODE> returns whether the type is signed or not. </LI>
<LI><CODE>shift</CODE> performs sign extension.
That is, right shifts fill the top bits with 1 if the number is negative
and with 0 otherwise.
(Since unsigned types are always positive, the top bit is always filled with
0.)</LI>
<LI>
Bits are numbered from 0 with bit 0 being the least significant bit.</LI>
<LI><CODE>shift x i</CODE> and <CODE>rotate x i</CODE> shift to the left if <CODE>i</CODE> is
positive and to the right otherwise.
</LI>
<LI><CODE>bit i</CODE> is the value with the i'th bit set.</LI>
</UL>
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