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

[Andreas Abel]

Restricting the domain of a function is common terminology in maths.  I 
like the original name 'restrict' or 'restrictTo' or 'restrictKeys'.

Intersection is a symmetric operation, so that name is less suitable, imho.

On 14.07.2016 17:41, amindfv at gmail.com wrote:
> +1 to the function, +1 to 'restrictKeys' or 'intersectKeys'
>
> Tom
>
>
> El 14 jul 2016, a las 11:01, Iavor Diatchki <iavor.diatchki at gmail.com
> <mailto:iavor.diatchki at gmail.com>> escribió:
>
>> 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
>> <mailto: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 <mailto:ivan.miljenovic at gmail.com>> wrote:
>>
>>         On 14 July 2016 at 22:45, Jake McArthur
>>         <jake.mcarthur at gmail.com <mailto: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 <mailto: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 <mailto:andreas.abel at gu.se>
>>         >> http://www2.tcs.ifi.lmu.de/~abel/
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>>
>>
>>         --
>>         Ivan Lazar Miljenovic
>>         Ivan.Miljenovic at gmail.com <mailto:Ivan.Miljenovic at gmail.com>
>>         http://IvanMiljenovic.wordpress.com
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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/