Proposal: Make Semigroup as a superclass of Monoid
M Farkas-Dyck
strake888 at gmail.com
Mon Mar 30 03:16:33 UTC 2015
On 29/03/2015 at 05:20:33 -0700, Jeremy wrote:
> 1. GHC 7.12 will include Semigroup and NonEmpty in base.
+1 for Semigroup at least.
NonEmpty is simply the cofree comonad of Maybe, so I think we ought to define it either as such or to be compatibly redefinitile as such, e.g.
now:
data NonEmpty a = a .: Maybe (NonEmpty a)
so potentially later:
data Cofree f a = a .: f (Cofree f a)
type NonEmpty = Cofree Maybe
as otherwise we shall have various code using nonsame isomorphic types which one must convert or coerce between for no good reason.
+1 for NonEmpty if so defined, -1 otherwise.
> 2. GHC >7.12 will define Monoid as a subclass of Semigroup.
+1
On 29/03/2015 at 11:23:19 -0400, David Feuer wrote:
> I guess I should get a dog in the fight—I think <> should be the Semigroup method.
+1
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