28 May
2013
28 May
'13
5:11 p.m.
On Tue, May 28, 2013 at 09:09:48PM +0200, Johannes Gerer wrote:
What about these two very simple type classes. Are they equivalent? [...] class Pointed f where pure :: a -> f a
class Unit f where unit :: f a a
newtype UnitPointed f a = UnitPointed f a a instance Unit f => Pointed (UnitPointed f) where pure f = UnitPointed unit
newtype Kleisli f a b = Kleisli (a -> f b) instance Pointed f => Unit (Kleisli f) where unit = Kleisli pure
This is implausible, since "pure f" does not depend on "f".