2009/5/8 Stephan Friedrichs
Hi!
When looking for an xor function, I found one in Data.Bits but couldn't use it for Bool, because Bool is no instance of Bits and of Num (which would be necessary, because it's "class (Num b) => Bits b"). My question is: Why not?
We could declare
instance Num Bool where (+) False = id (+) True = not
(*) True True = True (*) _ _ = False
(-) = (+)
negate = id abs = id signum = const True fromInteger = not . even
which basically implements the field with 2 elements and
instance Bits Bool where bitSize = const 1 isSigned = const False
(.&.) = (&&) (.|.) = (||) xor = (+)
complement = not
shift = const shiftL = const shiftR = const
rotate = const rotateL = const rotateR = const
bit = (==0)
setBit _ 0 = True setBit b _ = b
clearBit _ 0 = False clearBit b _ = b
complementBit b 0 = not b complementBit b _ = b
testBit b 0 = b testBit _ _ = False
quite trivial... Why is this not part of base? Or am I missing something?
//Stephan
Isn't "XOR" for booleans (/=)? Deniz Dogan