Err, I'm not seeing the danger of this (+) :: forall a. (Num a) => a -> a -> a Doesn't this require the two parameters to be the same instance of Num? On Fri, May 8, 2009 at 10:51 AM, Sittampalam, Ganesh < ganesh.sittampalam@credit-suisse.com> wrote:
Stephan Friedrichs wrote:
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?
[...] quite trivial... Why is this not part of base? Or am I missing something?
One reason would be that we don't want 1 + True to typecheck, even if it does have a sensible interpretation.
Ganesh
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