Re: Add newtype for Alternative using QuantifiedConstraints in base-4.13

It'll have to use the underlying Functor and Applicative to get an Alternative. Could you give some examples where you'd like to use this? I don't like the name but don't have a better one off the top of my head. AltMonoid or something? On Sat, 16 Feb 2019 at 10:20, theindigamer wrote:

I'm not sure which implementation you have in mind - the newtype one? I suppose that it would be harmless to add it in, although I don't immediately see the use case.

On Fri, Feb 15, 2019 at 7:11 PM Carter Schonwald wrote:

...

this looks quite pretty, though I must admit that im not the most savvy at quantified constraints yet

wouldn't this newtype also benefit from a semigroup and monoid instance too? (or am I overlooking some reason why you can't do them too?)

On Fri, Feb 15, 2019 at 7:05 PM theindigamer wrote:

...

Thoughts on adding a newtype with the following Alternative instance?

(The name chosen is a placeholder, I don't have any particular preference).

newtype Mon f a = Mon { unMon :: f a }

instance (forall a. Monoid (f a)) => Alternative (Mon f) where empty = Mon mempty (<|>) (Mon m1) (Mon m2) = Mon (m1 <> m2)

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