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

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 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@gmail.com> wrote:

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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

On 14 July 2016 at 22:45, Jake McArthur wrote: the

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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).

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On Thu, Jul 14, 2016, 5:39 AM Andreas Abel wrote:

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+1.

On 14.07.2016 06:45, David Feuer wrote:

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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.

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Department of Computer Science and Engineering Chalmers and Gothenburg University, Sweden

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