[Haskell-cafe] Why is Bool no instance of Num and Bits?
nccb2 at kent.ac.uk
Fri May 8 12:00:17 EDT 2009
Neil Mitchell wrote:
> I didn't at first, then I remembered:
> 1 + True
> fromInteger 1 + True
> And if we have Num for Bool, it type checks.
Does that also mean that you could write:
if 3 - 4 then ... else ... (= if (fromInteger 3 :: Bool) - (fromInteger
4 :: Bool) then ... else ...)
or perhaps (not sure if type defaulting stretches to this):
if 1 then ... else ... (= if (fromInteger 1 :: Bool) then ... else ...)
If you change fromInteger in Num Bool to be fromInteger x = x /= 0, then
we could all start writing nasty C-like if-expressions...
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