Add newtype for Alternative using QuantifiedConstraints in base-4.13

[theindigamer]

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 <carter.schonwald at gmail.com>
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 <theindigamer15 at gmail.com>
> 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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