Proposal: Add `restriction` to Data.Map and Data.IntMap

[Iavor Diatchki]

I've also needed this in the past, so +1.

I think the bike-shed should be colored:  intersectKeys or restrictKeys

-Iavor

On Thu, Jul 14, 2016 at 6:39 AM, Edward Kmett <ekmett at gmail.com> wrote:

> +1 on the functionality, not a fan of the name.
>
> Bikeshed color: intersectionWithSet?
>
> -Edward
>
> On Thu, Jul 14, 2016 at 9:36 AM, Ivan Lazar Miljenovic <
> ivan.miljenovic at gmail.com> wrote:
>
>> On 14 July 2016 at 22:45, Jake McArthur <jake.mcarthur at gmail.com> wrote:
>> > I like the function, but I'd like to bikeshed a bit. The name
>> "restriction"
>> > seems confusing to me, or at least I don't understand the etymology. As
>> of
>> > now I'd prefer something like "filterMember". filterMember is to
>> (filter .
>> > flip member) as concatMap is to (concat . map). That's not perfectly
>> > consistent due to the flip, but I think it's close enough to motivate
>> the
>> > name.
>>
>> More possible bikeshed colours:
>>
>> * intersectionWith/setIntersection to reflect the similarity with the
>> existing intersection functions
>>
>> * restrictTo (which may fit better with the proposed argument order
>> than the ones above)
>>
>> If we keep this argument order, then I think a name similar to
>> restriction as originally proposed makes more sense than an
>> intersection one (as the arguments are flipped compared to the other
>> similarly named functions).
>>
>> >
>> >
>> > On Thu, Jul 14, 2016, 5:39 AM Andreas Abel <abela at chalmers.se> wrote:
>> >>
>> >> +1.
>> >>
>> >> On 14.07.2016 06:45, David Feuer wrote:
>> >> > Cale Gibbard proposes the following:
>> >> >
>> >> > Data.IntMap.restriction :: IntSet -> IntMap a -> IntMap a
>> >> > Data.Map.restriction :: Ord k => Set k -> Map k a -> Map k a
>> >> >
>> >> > In each case, the map is filtered to contain only the keys that are
>> >> > also found in the set. This can be implemented efficiently using a
>> >> > slightly stripped-down version of Data.Map.intersection.
>> >> >
>> >> > David Feuer
>> >> > _______________________________________________
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>> >> >
>> >>
>> >>
>> >> --
>> >> Andreas Abel  <><      Du bist der geliebte Mensch.
>> >>
>> >> Department of Computer Science and Engineering
>> >> Chalmers and Gothenburg University, Sweden
>> >>
>> >> andreas.abel at gu.se
>> >> http://www2.tcs.ifi.lmu.de/~abel/
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>> >
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>>
>>
>>
>> --
>> Ivan Lazar Miljenovic
>> Ivan.Miljenovic at gmail.com
>> http://IvanMiljenovic.wordpress.com
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>
>
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