Alwyn just pointed out another use-case as well.
If there is either a @discardableResult or two variants (one which returns a
result) where the method returns the items being removed (which is to be
expected of a method named “remove”), then it becomes useful in ways which
filter alone is not. Here is how it would be used with a use-case from a
project I was working on this weekend:
var longWords = allWords //A very long list of words passed as a
parameter
let shortWords = longWords.remove(where: {$0.characters.count < 4})
compare that to either filtering twice:
let longWords = allWords.filter({$0.characters.count >= 4})
let shortWords = allWords.filter({$0.characters.count < 4}) //We are
looping over a very long list twice
or what I ended up doing:
var longWords:[String] = []
var shortWords:[String] = []
for word in allWords {
if word.characters.count < 4 {
shortWords.append(word)
}else{
longWords.append(word)
}
}
Thanks,
Jon
> On Sep 26, 2017, at 2:59 AM, Xiaodi Wu <[email protected]> wrote:
>
>
> On Tue, Sep 26, 2017 at 00:15 Jonathan Hull <[email protected]
> <mailto:[email protected]>> 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
>> <[email protected] <mailto:[email protected]>> wrote:
>>
>> What is the use case?
>> On Mon, Sep 25, 2017 at 23:27 Félix Cloutier <[email protected]
>> <mailto:[email protected]>> 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 <[email protected]
>>> <mailto:[email protected]>> a écrit :
>>>
>>> On Mon, Sep 25, 2017 at 4:55 PM, Xiaodi Wu <[email protected]
>>> <mailto:[email protected]>> 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
>>> <[email protected] <mailto:[email protected]>> 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
>>>> <[email protected] <mailto:[email protected]>> 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
>>>> <https://github.com/apple/swift/pull/12058>
>>>>
>>>> Any thoughts/suggestions on this are appreciated.
>>>>
>>>> Thanks!
>>>>
>>>> Alwyn
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
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>>>> <https://lists.swift.org/mailman/listinfo/swift-evolution>
>>>
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