21 Dec
2020
21 Dec
'20
1:54 p.m.
On Mon, Dec 21, 2020 at 07:19:49PM +0100, Ben Franksen wrote:
So, a simple type class Boolean with instances for Bool and functions returning Booleans should cover the majority of use cases; more instances could be added of course. Something like [...] instance Boolean Bool where (&&) = (Prelude.&&) (||) = (Prelude.||) not = Prelude.not top = True bottom = False
instance Boolean b => Boolean (a->b) where (f && g) x = f x && g x (f || g) x = f x || g x (not f) x = not (f x) top = const top bottom = const bottom
I think it's worth seeing more instances. As it is I don't understand in what situations one would use these polymorphically and therefore why `liftA2 (&&)`, `fmap not`, `pure True` and friends wouldn't suffice. Tom