Control.Monad proposal: Add whenJust

Carter Schonwald carter.schonwald at gmail.com
Mon May 20 01:54:54 CEST 2013


Good idea, though each channel / fora seems to have slightly disjoint sub
communities.

On Sunday, May 19, 2013, Anthony Cowley wrote:

> On May 19, 2013, at 10:33 AM, Edward Kmett <ekmett at gmail.com<javascript:_e({}, 'cvml', 'ekmett at gmail.com');>>
> 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 think this issue may be too big to rely on mailing list +1s. Is there
> any precedent for having a web-based poll of some sort? We often get more
> engagement in debates on IRC and /r/haskell than the mailing list, so let's
> not let the choice of forum drive the result.
>
> Anthony
>
>
>
>
> 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<javascript:_e({}, 'cvml', 'jwlato at gmail.com');>
> > wrote:
>
>>
>> On May 18, 2013 10:09 PM, "Ian Lynagh" <ian at well-typed.com<javascript:_e({}, 'cvml', '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<javascript:_e({}, 'cvml', '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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