Remove redundant Functor constraint from StateT Applicative/Alternative instances

[Baldur Blöndal]

1) is good, I assume 3) will happen once the dust settles on AMP

2016-11-22 8:56 GMT+00:00 Edward Kmett <ekmett at gmail.com>:

> They could be CPP'd around on newer versions, sure, at the cost of a fair
> bit of noise in the source code. Presumably it was considered simpler to
> just have one type signature. I've CC'd Ross Paterson, the maintainer of
> transformers. Ultimately it comes down to a 3 way decision between 1.)
> cleaner code by keeping the status quo, or 2.) cleaner haddocks by changing
> the code as requested here conditionally with CPP, or 3.) loss of backwards
> compatibility by just changing the type completely.
>
> I don't particularly care which of the first two options are taken -- and
> the first even has the benefit of requiring zero labor -- but I think it'd
> be a bad idea to lose backwards compatibility by taking the third.
>
> -Edward
>
>
> On Mon, Nov 21, 2016 at 5:52 PM, Baldur Blöndal <baldurpet at gmail.com>
> wrote:
>
>> Does this belong here? Applicative [1] and Alternative [2] instances of
>> StateT have redundant constraints
>>
>> > instance (Functor m, Monad     m) => Applicative (StateT s m)
>> > instance (Functor m, MonadPlus m) => Alternative (StateT s m)
>>
>> The Functor constraint may be removed
>>
>> [1] https://hackage.haskell.org/package/transformers-0.5.2.0/doc
>> s/src/Control.Monad.Trans.State.Lazy.html#line-201
>> [2] https://hackage.haskell.org/package/transformers-0.5.2.0/doc
>> s/src/Control.Monad.Trans.State.Lazy.html#line-210
>>
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>
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