On Sunday 16 October 2011, 02:33:58, Bas van Dijk wrote:
However having zero and one as methods almost brings us overloaded booleans. In that regard it would be better to name them false and true though. Ideally we would split Bits into:
class Boolean b where false :: b true :: b
-- Nice in combination with RebindableSyntax: ifThenElse :: b -> a -> a -> a
-- Probably does not have to be a method: not :: b -> b not b = ifThenElse b false true
(.&.) :: b -> b -> b x .&. y = ifThenElse x (ifThenElse y true) false
(.|.) :: b -> b -> b x .|. y = ifThenElse x true (ifThenElse y true false)
The Bits class then becomes:
class Boolean b => Bits b where the (.&.), (.|.) are removed because they are defined in Boolean.
I don't like that. instance Boolean Int where ??? The default methods for (.&.), (.|.) and not would yield quite surprising behaviour. And Int shouldn't be a member of class Boolean anyway.
But an important question is: is it wise to treat booleans and bits equally?
IMO, it isn't.
Because this would allow something like:
{-# LANGUAGE RebindableSyntax #-}
foo = if 1 then 2 else 3
Yech!