[swift-evolution] Additional methods for removing elements from a collection in Swift

[Xiaodi Wu]

On Tue, Sep 26, 2017 at 00:15 Jonathan Hull <jhull at gbis.com> wrote:

> As he says, it is an in-place equivalent of filter, so the use-cases would
> be similar.  I could see this being extremely useful.  Off the top of my
> head:
>
> views.remove(where: {$0.isHidden}) //Remove all views which are hidden
> from the list.
>

Is such a method ever going to be different (in performance, say) from:

views = Views(views.lazy.filter { $0.isHidden })

Another thing which seems to be missing (although it could be there and I
> don’t know the name) is the ability to split a list into two using a filter
> (one with the filtered items and one with the remainder).  I am surprised
> every time I reach for it and it isn’t there (the last time being
> yesterday).
>
> Thanks,
> Jon
>
>
>
> On Sep 25, 2017, at 9:55 PM, Xiaodi Wu via swift-evolution <
> swift-evolution at swift.org> wrote:
>
> What is the use case?
> On Mon, Sep 25, 2017 at 23:27 Félix Cloutier <felixcloutier at icloud.com>
> wrote:
>
>> Actually, IMO, it's an oversight that there's no remove(where:), or
>> another in-place equivalent to `filter`. I'm in favor of it.
>>
>> Félix
>>
>>
>> Le 25 sept. 2017 à 15:17, Xiaodi Wu <xiaodi.wu at gmail.com> a écrit :
>>
>> On Mon, Sep 25, 2017 at 4:55 PM, Xiaodi Wu <xiaodi.wu at gmail.com> wrote:
>>
>>> Brent has a great proposal in the pipeline regularizing the names of
>>> some of these functions and filling in some of the more glaring gaps.
>>>
>>> With regard to the specific items proposed here, Felix shows that
>>> ‘filter’ provides an idiomatic one-line way of doing some of what is
>>> proposed; currently remove(index(of:)) and operating on sliced would
>>> accomplish the rest. Therefore, I do not think these proposed additions
>>> meet the very high bar for expansion of the standard library API.
>>
>>
>> I should add, however, it is wonderful (IMO) that more people are
>> thinking about these APIs; welcome and thank you for restarting this very
>> important conversation. It would be nice to get some more eyeballs on the
>> previously discussed set of rationalizations to the Collection APIs so that
>> we can make their use a little more ergonomic--with any luck, some better
>> names for existing extension methods and filling in a very few gaps
>> judiciously would allow us to make the existing facilities sufficiently
>> more discoverable that it will be easier to accomplish what you seek
>> without adding more extensions.
>>
>>
>> On Mon, Sep 25, 2017 at 11:14 Félix Cloutier via swift-evolution <
>>> swift-evolution at swift.org> wrote:
>>>
>>>> Another alternative is to use `array = array.filter { $0 != someElement
>>>> }`.
>>>>
>>>> I thought that there would be a `remove(where:)` method, but there
>>>> isn't.
>>>>
>>>> Félix
>>>>
>>>> Le 25 sept. 2017 à 02:12, Alwyn Concessao via swift-evolution <
>>>> swift-evolution at swift.org> a écrit :
>>>>
>>>> Hello,
>>>>
>>>> After going through the Swift standard library functions provided for
>>>> removing elements from a collection, one common pattern can be observed in
>>>> all those functions and that is the functions provide to remove elements
>>>> from the collection by passing the position or index of the element or
>>>> passing a range of indices or positions to remove the elements.The standard
>>>> library does not provide options to remove an element from a collection by
>>>> passing the actual element  to be removed directly to the remove
>>>> method.I've encountered this situation many times when programming in Swift
>>>> wherein I want an element or a set of elements to be removed directly
>>>> without always accessing it's index in the collection but I have always
>>>> ended up having to first access the index of the element or elements which
>>>> I want to remove and then pass that index to the remove method.
>>>>
>>>> The idea is to have an extension of the RangeReplaceableCollection
>>>> protocol to include a method to remove elements from a collection by
>>>> passing directly the element to be removed to the remove method and also
>>>> include methods to remove multiple elements from the collection by passing
>>>> in a sequence of the elements to be removed to the remove method and to
>>>> remove an element in a particular subrange of the collection.
>>>>
>>>> The prototype of the methods will be as follows -
>>>>
>>>> extension RangeReplaceableCollection where Element:Equatable{
>>>>
>>>> mutating func removeElement(_ elementToBeRemoved:Element){
>>>>
>>>> //check if elementToBeRemoved exists ;if yes, remove all occurrences of
>>>> elementsToBeRemoved from the collection.
>>>>
>>>> }
>>>>
>>>> mutating func removeElementInSubrange(_ elementToBeRemoved:Element,in
>>>> range:Range<Index>){
>>>>
>>>> //check if elementoBeRemoved exists; if yes, check if the index of
>>>> elementToBeRemoved is part of the subrange, if yes then remove else don't
>>>> remove.
>>>>
>>>> }
>>>>
>>>> mutating func removeContentsOf<C:Collection>(_ elementsToBeRemoved:C){
>>>>
>>>> //check if each element in the elementsToBeRemoved sequence exists in
>>>> the collection, if the element exists, remove it.
>>>>
>>>> }
>>>>
>>>> I've implemented the above in the pull request
>>>> https://github.com/apple/swift/pull/12058
>>>>
>>>> Any thoughts/suggestions on this are appreciated.
>>>>
>>>> Thanks!
>>>>
>>>> Alwyn
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
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>>>
>>
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