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

[Tony Allevato]

On Wed, Sep 27, 2017 at 10:36 AM Ben Cohen via swift-evolution <
swift-evolution at swift.org> wrote:

>
>
> On Sep 25, 2017, at 2:12 AM, Alwyn Concessao via swift-evolution <
> swift-evolution at swift.org> wrote:
>
> 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.
>
> }
>
>
> Hi Alwyn,
>
> In general, we try to avoid methods on Collection in the standard library
> that take a limiting range to operate on.
>

This is something of a related aside, but since you mentioned it, is this
also the reason that there is no method like `index(of element: Element,
from index: Index) -> Index?`?

In those situations where I've needed to do that (e.g., a while loop that
skips from match to match) I end up falling back to slices, but
historically it's been somewhat awkward to write compared to the code I
would write if such a function exists.

That being said, I don't believe I've tried it since Swift 4 introduced the
new partial range operators so it's possible that those simplify the
pattern quite a bit.



> Instead, the user can slice the collection using the range, then call the
> mutating method on the slice. If done directly on the subscript, this has
> the effect of mutating the parent collection:
>
> var a = Array(0..<10)
> let isEven = { $0%2 == 0 }
>
> a[3...].remove(where: isEven)
> // a = [0, 1, 2, 3, 5, 7, 9]
>
> The downside of this today is that it can be inefficient, because the
> mutated slice might be copied as part of the mutaate-and-write-back. But
> there are changes slated for Swift 5 that should allow this mutation to
> happen in place.
>
>
> _______________________________________________
> 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/20170927/28de5356/attachment.html>