[swift-evolution] [Proposal] Add Array binary search to the standard library

[Xiaodi Wu]

Hi Igor,

Since your proposal would be additive, it probably wouldn't be considered
for review until the next phase of Swift evolution.

My read of the core team's feedback is that some binary search
functionality is welcome, but it's a question of *how* it's designed. When
purely additive changes are in scope, a successful proposal will likely
address the weaknesses of the previous proposal. Since that proposal
considered as an alternative a design such as yours, but it concluded that
a different design was better, you'll probably want to address why you
think this API design is best, or alternatively, you may want to study the
alternatives presented in that proposal and refine them to be better.
On Wed, Sep 7, 2016 at 05:16 Igor Vasilenko via swift-evolution <
swift-evolution at swift.org> wrote:

> do you mean this?
>
> public func binarySearch<T: Comparable>(array: [T], key: T, range: Range<Int>, sorted: Bool) -> Int?
>
> Best regards, Igor Vasilenko
>
> iOS Developer at Yota
>
> +7 (999) 527 - 07 - 59
> spb.vasilenko at gmail.com <name.surname at e-legion.com>
> www.spbvasilenko.github.io <http://www.e-legion.com/>
>
>
>
>
>
>
>
>
> On 07 Sep 2016, at 13:08, Guillaume DIDIER <
> guillaume.didier.2014 at polytechnique.org> wrote:
>
> Basically for a binary search to work it needs to operate on a sorted
> array (it is a necessary invariant).
>
> It is really interesting when you make a lot of search in the same sorted
> array, hence I would +1 the sorted array, with initializer from an array.
>
>
> *Guillaume  DIDIER*
> —
> *ÉCOLE POLYTECHNIQUE*
> 91128 PALAISEAU CEDEX
> M. +33 (0)7 70 43 18 40
> guillaume.didier at polytechnique.edu
> <guillaume.didier at polytechnique.edu?subject=>
> www.polytechnique.edu
> —
>
> Le 7 sept. 2016 à 12:04, Haravikk via swift-evolution <
> swift-evolution at swift.org> a écrit :
>
>
> On 7 Sep 2016, at 10:08, Charlie Monroe via swift-evolution <
> swift-evolution at swift.org> wrote:
>
> Aside from this being additive (i.e. out of scope for Swift 4), this
> requires the array to be sorted in order for the search to work - who will
> guarantee this? The caller? What happens when this is called on an array
> that is not sorted? You likely get nil, while the item is in the array
> (false negative).
>
> This would probably make sense by not extending Array itself, but
> introducing SortedArray which would automatically keep its members sorted
> instead - this way there would be a guarantee that the array is sorted and
> the user won't have to deal with sorting the array. It would however be at
> the cost of O(log N) for insertion…
>
>
> I don't think this is really a problem, just needs to be clear that
> behaviour is undefined if the array wasn't previously sorted (or not in the
> same order).
>
> On this topic there was a previous proposal that was undergoing
> refinements after being initially rejected, you can find it here:
>
> https://github.com/apple/swift-evolution/blob/master/proposals/0074-binary-search.md
> _______________________________________________
> swift-evolution mailing list
> swift-evolution at swift.org
> https://lists.swift.org/mailman/listinfo/swift-evolution
>
>
>
> _______________________________________________
> swift-evolution mailing list
> swift-evolution at swift.org
> https://lists.swift.org/mailman/listinfo/swift-evolution
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-evolution/attachments/20160907/7bf137ae/attachment.html>