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

Tue Sep 26 15:16:16 CDT 2017

Sent from my iPhone

> On Sep 25, 2017, at 22:16, Jonathan Hull via swift-evolution <swift-evolution at swift.org> 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.
> 
> 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).  
> 

There’s partition(by:), which gives you an index that you can split with. 

> 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
>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>>>> _______________________________________________
>>>>>>> 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
>>>> 
>>> 
>> _______________________________________________
>> 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/20170926/551512db/attachment.html>