> review of SE-0174 "Change `filter` to return an associated type"
>
> What is your evaluation of the proposal?
I think a change in this 'area' is valuable because currently always returning
an array from collection operations is limiting. However I think this proposal
feels like 'papering' over problems rather than fixing the root cause. I think
it would be better to reject this and do two more adventurous proposals instead:
1. Allow protocols to be generic, instead of associated types, so that you
can write Sequence<T>
2. Allow Self to accept a generic argument, so that you can write Self<T>
With these to, admittedly much more major changes, you can then write:
protocol Sequence<T> {
func filter(_ isIncluded: (T) throws -> Bool) rethrows -> Sequence<T>
func map<M>(_ mapper: (T) throws -> M) rethrows -> Sequence<M>
}
extension RangeReplaceableCollection {
func filter(_ isIncluded: (T) throws -> Bool) rethrows -> Self<T> {
var result = Self<T>()
for element in self {
if try isIncluded(element) {
result.append(element)
}
}
return result
}
func map<M>(_ mapper: (T) throws -> M) rethrows -> Self<M> {
var result = Self<M>()
for element in self {
try result.append(mapper(element))
}
return result
}
}
Which I think both reads better and is more powerful since it allows map to be
written also.
> Is the problem being addressed significant enough to warrant a change to
> Swift?
Yes, return an array is a real pain
> Does this proposal fit well with the feel and direction of Swift?
Yes and no, really smacks of papering over other flaws. Might box Swift into a
corner were other problems can't be fixed because the underlying, real,
problems still remain.
> If you have used other languages or libraries with a similar feature, how do
> you feel that this proposal compares to those?
Virtually all other languages I have used, e.g. Java, Scala, use the solution I
presented above.
> How much effort did you put into your review? A glance, a quick reading, or
> an in-depth study?
Have been bitten by this and have written my own collection hierarchy to
overcome this limitation, and others, of the current library.
-- Howard.
> On 29 Apr 2017, at 10:06 am, Douglas Gregor <[email protected]> wrote:
>
> Hello Swift community,
>
> The review of SE-0174 "Change `filter` to return an associated type" begins
> now and runs through May 3, 2017. The proposal is available here:
>
> https://github.com/apple/swift-evolution/blob/master/proposals/0174-filter-range-replaceable.md
> Reviews are an important part of the Swift evolution process. All reviews
> should be sent to the swift-evolution mailing list at
>
> https://lists.swift.org/mailman/listinfo/swift-evolution
> or, if you would like to keep your feedback private, directly to the review
> manager. When replying, please try to keep the proposal link at the top of
> the message:
>
> Proposal link:
>
> https://github.com/apple/swift-evolution/blob/master/proposals/0174-filter-range-replaceable.md
> Reply text
> Other replies
> What goes into a review?
>
> The goal of the review process is to improve the proposal under review
> through constructive criticism and, eventually, determine the direction of
> Swift. When writing your review, here are some questions you might want to
> answer in your review:
>
> What is your evaluation of the proposal?
> Is the problem being addressed significant enough to warrant a change to
> Swift?
> Does this proposal fit well with the feel and direction of Swift?
> If you have used other languages or libraries with a similar feature, how do
> you feel that this proposal compares to those?
> How much effort did you put into your review? A glance, a quick reading, or
> an in-depth study?
> More information about the Swift evolution process is available at
>
> https://github.com/apple/swift-evolution/blob/master/process.md
> Thank you,
>
> -Doug Gregor
>
> Review Manager
>
> _______________________________________________
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