[swift-evolution] [Review] SE-0065 A New Model for Collections and Indices

[Tony Parker]

> On Apr 10, 2016, at 2:41 PM, Chris Lattner via swift-evolution <swift-evolution at swift.org> wrote:
> 
> Hello Swift community,
> 
> The review of "A New Model for Collections and Indices" begins now and runs through April 18th. The proposal is available here:
> 
> 	https://github.com/apple/swift-evolution/blob/master/proposals/0065-collections-move-indices.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.
> 
> 
> 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?

I agree with the general direction and scope of the proposal, but I think the names could use some changes. Specifically, I don’t think the fallback to ‘form’ is required. It would be a significant readability improvement to use a meaningful verb to describe the action of altering the argument. The methods that create new indices probably need a label on the first argument, because otherwise it looks as if the IndexDistance is what is described by ‘index’.

Proposed:

  func successor(of i: Index) -> Index
  func formSuccessor(i: inout Index)

Instead, I suggest:

  func successor(of i : Index) -> Index
  func advance(i: inout Index)

Proposed:

  func index(n: IndexDistance, stepsFrom i: Index) -> Index
  func index(n: IndexDistance, stepsFrom i: Index, limitedBy limit: Index) -> Index
  func formIndex(n: IndexDistance, stepsFrom i: inout Index)
  func formIndex(n: IndexDistance, stepsFrom i: inout Index, limitedBy limit: Index)

Suggested (taking into account Nate’s suggestion of reversing the order):

  func index(startingAt i: Index, movedBy n: IndexDistance) -> Index
  func index(startingAt i: Index, movedBy n: IndexDistance, limitedBy limit: Index) -> Index
  func move(i : inout Index, by n: IndexDistance)
  func move(i : inout Index, by n: IndexDistance, limitedBy limit: Index)

Proposed:

  func predecessor(of i: Index) -> Index
  func formPredecessor(i: inout Index)

Suggested:

  func predecessor(of i: Index) -> Index
  func reverse(i: inout Index)


I think reversing an index has some nice symmetry with reversing a sequence, but if it seems to confusing, then replace advance and reverse with ‘moveForward’ and ‘moveBackward’.

- Tony

> 	* 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 you 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,
> 
> -Chris Lattner
> Review Manager
> 
> 
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