Control.Monad proposal: Add whenJust

[Edward Kmett]

Well, it so far has definitely put the preponderance of weight of opinion
on just replacing the definitions in the Prelude with Foldable and
Traversable definitions.

I do think we should probably move it to another topic, as we're definitely
not talking about whenJust. (In particular a +1 on this stuff is
effectively a -1 on the original topic!)


On Sun, May 19, 2013 at 7:00 PM, Carter Schonwald <
carter.schonwald at gmail.com> wrote:

> Do the additional votes on foldable / traversable change the outcome?
>
>
> On Sunday, May 19, 2013, Edward Kmett wrote:
>
>> The main utility in removing the crippled versions entirely is that you
>> don't wind up with conflict, but if they are already gone then there is no
>> conflict (within base) in moving the existing Foldable and Traversable
>> interfaces into the Prelude.
>>
>> I did say when I made the suggestion that I didn't think it'd make it
>> past the objections, though.
>>
>> I'm personally against removing the existing mapM, etc. definitions from
>> the Prelude without replacing them with the combinators from
>> Foldable/Traversable as it would break strictly more code, and breaks a lot
>> more combinators than you would think, concat, sum, product, etc. are all
>> redefined in Foldable to be more general.
>>
>> 5 +1 votes for just fixing the Prelude to swap in the definitions from
>> Foldable and Traversable.
>>
>> 3 +1 votes for removing everything that conflicts with Foldable and
>> Traversable from the Prelude.
>>
>> And 2 votes against doing anything.
>>
>> At this point it is clear that no position has won more than a plurality
>> of the popular opinion, so I resignedly retract the proposal and let the
>> vocal 20% win.
>>
>> -Edward
>>
>>
>> On Sat, May 18, 2013 at 8:02 PM, John Lato <jwlato at gmail.com> wrote:
>>
>>>
>>> On May 18, 2013 10:09 PM, "Ian Lynagh" <ian at well-typed.com> wrote:
>>> >
>>> > On Wed, May 15, 2013 at 10:40:45PM +0200, Bas van Dijk wrote:
>>> > > On 15 May 2013 18:14, Edward Kmett <ekmett at gmail.com> wrote:
>>> > > > Personally, I'd be all for just moving Foldable (and Traversable)
>>> into the
>>> > > > Prelude and retiring the monomorphic versions of the functions
>>> they supply.
>>> >
>>> > I'd prefer to remove the monomorphic functions, but not to add anything
>>> > to Prelude.
>>>
>>> +1 to Ian's suggestion.
>>>
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>>
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