<div dir="ltr">On Sat, Sep 2, 2017 at 12:27 AM, Douglas Gregor via swift-evolution <span dir="ltr"><<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>></span> wrote:<br><div class="gmail_extra"><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex"><div style="word-wrap:break-word"><p style="box-sizing:border-box;margin-top:0px;margin-bottom:16px;color:rgb(36,41,46);font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Helvetica,Arial,sans-serif,"Apple Color Emoji","Segoe UI Emoji","Segoe UI Symbol";font-size:16px;background-color:rgb(255,255,255)">Hello Swift community,</p><p style="box-sizing:border-box;margin-top:0px;margin-bottom:16px;color:rgb(36,41,46);font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Helvetica,Arial,sans-serif,"Apple Color Emoji","Segoe UI Emoji","Segoe UI Symbol";font-size:16px;background-color:rgb(255,255,255)">The review of SE-0184 "Unsafe[Mutable][Raw][Buffer]<wbr>Pointer: add missing methods, adjust existing labels for clarity, and remove deallocation size" begins now and runs through September 7, 2017. The proposal is available here:</p><blockquote style="box-sizing:border-box;margin:0px 0px 16px;padding:0px 1em;border-left-width:0.25em;border-left-style:solid;border-left-color:rgb(223,226,229);background-color:rgb(255,255,255)"><div style="box-sizing:border-box;margin-top:0px;margin-bottom:0px"><font color="#6a737d" face="-apple-system, BlinkMacSystemFont, Segoe UI, Helvetica, Arial, sans-serif, Apple Color Emoji, Segoe UI Emoji, Segoe UI Symbol" size="3"><a href="https://github.com/apple/swift-evolution/blob/master/proposals/0184-unsafe-pointers-add-missing.md" target="_blank">https://github.com/apple/<wbr>swift-evolution/blob/master/<wbr>proposals/0184-unsafe-<wbr>pointers-add-missing.md</a></font></div></blockquote><p style="box-sizing:border-box;margin-top:0px;margin-bottom:16px;color:rgb(36,41,46);font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Helvetica,Arial,sans-serif,"Apple Color Emoji","Segoe UI Emoji","Segoe UI Symbol";font-size:16px;background-color:rgb(255,255,255)">Reviews are an important part of the Swift evolution process. All reviews should be sent to the swift-evolution mailing list at</p><blockquote style="box-sizing:border-box;margin:0px 0px 16px;padding:0px 1em;color:rgb(106,115,125);border-left-width:0.25em;border-left-style:solid;border-left-color:rgb(223,226,229);font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Helvetica,Arial,sans-serif,"Apple Color Emoji","Segoe UI Emoji","Segoe UI Symbol";font-size:16px;background-color:rgb(255,255,255)"><div style="box-sizing:border-box;margin-top:0px;margin-bottom:0px"><a href="https://lists.swift.org/mailman/listinfo/swift-evolution" style="box-sizing:border-box;background-color:transparent;color:rgb(3,102,214);text-decoration:none" target="_blank">https://lists.swift.org/<wbr>mailman/listinfo/swift-<wbr>evolution</a></div></blockquote><p style="box-sizing:border-box;margin-top:0px;margin-bottom:16px;color:rgb(36,41,46);font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Helvetica,Arial,sans-serif,"Apple Color Emoji","Segoe UI Emoji","Segoe UI Symbol";font-size:16px;background-color:rgb(255,255,255)">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:</p><blockquote style="box-sizing:border-box;margin:0px 0px 16px;padding:0px 1em;border-left-width:0.25em;border-left-style:solid;border-left-color:rgb(223,226,229);background-color:rgb(255,255,255)"><p style="color:rgb(106,115,125);font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Helvetica,Arial,sans-serif,"Apple Color Emoji","Segoe UI Emoji","Segoe UI Symbol";font-size:16px;box-sizing:border-box;margin-top:0px;margin-bottom:16px">Proposal link:</p><blockquote style="box-sizing:border-box;margin:0px;padding:0px 1em;border-left-width:0.25em;border-left-style:solid;border-left-color:rgb(223,226,229)"><div style="box-sizing:border-box;margin-top:0px;margin-bottom:0px"><font color="#6a737d" face="-apple-system, BlinkMacSystemFont, Segoe UI, Helvetica, Arial, sans-serif, Apple Color Emoji, Segoe UI Emoji, Segoe UI Symbol" size="3"><a href="https://github.com/apple/swift-evolution/blob/master/proposals/0184-unsafe-pointers-add-missing.md" target="_blank">https://github.com/apple/<wbr>swift-evolution/blob/master/<wbr>proposals/0184-unsafe-<wbr>pointers-add-missing.md</a></font></div></blockquote></blockquote><blockquote style="box-sizing:border-box;margin:0px 0px 16px;padding:0px 1em;color:rgb(106,115,125);border-left-width:0.25em;border-left-style:solid;border-left-color:rgb(223,226,229);font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Helvetica,Arial,sans-serif,"Apple Color Emoji","Segoe UI Emoji","Segoe UI Symbol";font-size:16px;background-color:rgb(255,255,255)"><div style="box-sizing:border-box;margin-top:0px;margin-bottom:0px">Reply text</div></blockquote><blockquote style="box-sizing:border-box;margin:0px 0px 16px;padding:0px 1em;color:rgb(106,115,125);border-left-width:0.25em;border-left-style:solid;border-left-color:rgb(223,226,229);font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Helvetica,Arial,sans-serif,"Apple Color Emoji","Segoe UI Emoji","Segoe UI Symbol";font-size:16px;background-color:rgb(255,255,255)"><blockquote style="box-sizing:border-box;margin:0px;padding:0px 1em;border-left-width:0.25em;border-left-style:solid;border-left-color:rgb(223,226,229)"><div style="box-sizing:border-box;margin-top:0px;margin-bottom:0px">Other replies</div></blockquote></blockquote><h5 style="box-sizing:border-box;margin-top:24px;margin-bottom:16px;font-size:0.875em;line-height:1.25;color:rgb(36,41,46);font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Helvetica,Arial,sans-serif,"Apple Color Emoji","Segoe UI Emoji","Segoe UI Symbol";background-color:rgb(255,255,255)"><a id="gmail-m_-3811060451040046695user-content-what-goes-into-a-review-1" class="gmail-m_-3811060451040046695anchor" href="https://github.com/apple/swift-evolution/pulls#what-goes-into-a-review-1" style="box-sizing:border-box;background-color:transparent;color:rgb(3,102,214);text-decoration:none;float:left;padding-right:4px;line-height:1" target="_blank"><u></u><u></u><u></u><u></u></a>What goes into a review?</h5><p style="box-sizing:border-box;margin-top:0px;margin-bottom:16px;color:rgb(36,41,46);font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Helvetica,Arial,sans-serif,"Apple Color Emoji","Segoe UI Emoji","Segoe UI Symbol";font-size:16px;background-color:rgb(255,255,255)">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:</p><ul style="box-sizing:border-box;padding-left:2em;margin-top:0px;margin-bottom:16px;color:rgb(36,41,46);font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Helvetica,Arial,sans-serif,"Apple Color Emoji","Segoe UI Emoji","Segoe UI Symbol";font-size:16px;background-color:rgb(255,255,255)"><li style="box-sizing:border-box">What is your evaluation of the proposal?</li></ul></div></blockquote><div>Overall, this is an improvement. However, I do have some questions and concerns:</div><div><br></div><div><br></div><div>Questions:</div><div><br></div><div>## UnsafeMutableRawPointer</div><div><br></div><div><div>Regarding the options given for "whose `count` to use"--which option is actually being proposed?</div><div><br></div><div>## UnsafeMutableBufferPointer</div><div><br></div><div>Please clarify: why are you proposing that the `at:` arguments in `UnsafeMutableBufferPointer` and `UnsafeMutableRawBufferPointer` _should not_ receive default values, but the `at:` arguments in `UnsafeMutableRawPointer` _should_ receive a default value of `0`?</div></div><div><br></div><div><br></div><div>Concerns:</div><div><br></div><div>## UnsafeMutablePointer</div><div><br></div><div>It's alarming that omitting `count` in `initialize(repeating:count:)` (and assign, etc.) means initialize _one_ element, but elsewhere (such as `UnsafeMutableBufferPointer` means initialize _all_ elements. The behavior of the proposed API also contradicts its own spelling on its face: `initialize(repeating: foo)` means *do not repeat* `foo`.</div><div><br></div><div>Yes, I understand the argument that `*BufferPointer` types have an intrinsic count, etc., but in the context of code where types are inferred, `let foo = T.allocate(capacity: 100); foo.initialize(repeating: bar)` should not mean one thing for `*BufferPointer` types and a totally different thing for plain `*Pointer` types--particularly when both can be allocated with a certain capacity greater than one.</div><div><br></div><div>Either `count` should always be required, or for convenience there should be a separate overload `initialize(pointee:)` that does not require `count`.</div><div><br></div><div><br></div><div>## UnsafeMutableRawBufferPointer</div><div><br></div><div>In `copyBytes`, the use of `Bytes` to emphasize that it's the memory that's being copied is thoughtful, but it is inconsistent with the other method names that use the terminology `Memory` for the same purpose (e.g., `moveInitializeMemory` to clarify the meaning of `moveInitialize`).</div><div><br></div><div>For better consistency--and since you're proposing to rename `copyBytes(from:count:)` on `UnsafeMutableRawPointer` to `copy(from:bytes:)`--this particular API on `UnsafeMutableRawBufferPointer` should be named `copyMemory(from:)` and not `copyBytes(from:)`.</div><div><br></div><div>Although, actually, looking at the APIs on `UnsafeMutableRawPointer` itself, that particular method too might best be written as `copyMemory(from:bytes:)` instead of merely `copy(from:bytes:)` for better consistency with the rest of the methods on that type as well.</div><div><br></div><div><br></div><div>## General comment</div><div><br></div><div><div>Many `at:` arguments, especially such as in the case of `copyBytes(at:from:)`, make sense only when read in a list with all other methods. Standing alone, `at` is ambiguous as to whether it's referring to the _source_ or the _destination_. Why do these APIs on `*BufferPointer` types not take advantage of subscripts? That is, why not:<br></div><div><br></div><div> `foo[x...].copyMemory(from: bar)`</div><div><br></div><div>instead of</div><div><br></div><div> `foo.copyBytes(at: x, from: bar)`</div><div><br></div><div>The first seems dramatically clearer as to its meaning. The same feedback applies to nearly all uses of `at` on `*BufferPointer` types: they would seem to be greatly clarified (in terms of the "what does `at` mean" question) by the use of a subscript spelling.</div><div><br></div><div>I notice that you comment that you feel there are ergonomic issues with buffer pointer slicing; can you please comment on what is "wasteful" currently? Is there a performance hit to slicing a `*BufferPointer` type? If so, we should fix that, as the whole rationale of having these types (as I understand it) is to improve the ergonomics of working with pointers to multiple elements by conforming them to `*Collection` APIs.</div><div><br></div><div>It seems deeply unsatisfactory to invent new methods that use `at:` arguments _on a type whose purpose is to expose `*Collection` APIs_ if we agree that the slicing notation is demonstrably clearer. I do not have the same concerns about adding `at:` arguments to `UnsafeMutableRawPointer` methods, which are quite appropriate.</div></div><div><br></div><div><br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex"><div style="word-wrap:break-word"><ul style="box-sizing:border-box;padding-left:2em;margin-top:0px;margin-bottom:16px;color:rgb(36,41,46);font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Helvetica,Arial,sans-serif,"Apple Color Emoji","Segoe UI Emoji","Segoe UI Symbol";font-size:16px;background-color:rgb(255,255,255)"><li style="box-sizing:border-box;margin-top:0.25em">Is the problem being addressed significant enough to warrant a change to Swift?</li></ul></div></blockquote><div>Yes.</div><div> <br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex"><div style="word-wrap:break-word"><ul style="box-sizing:border-box;padding-left:2em;margin-top:0px;margin-bottom:16px;color:rgb(36,41,46);font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Helvetica,Arial,sans-serif,"Apple Color Emoji","Segoe UI Emoji","Segoe UI Symbol";font-size:16px;background-color:rgb(255,255,255)"><li style="box-sizing:border-box;margin-top:0.25em">Does this proposal fit well with the feel and direction of Swift?</li></ul></div></blockquote><div>In parts, yes. In others (see above), it could be improved to fit better with the feel and direction of other Swift APIs.</div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex"><div style="word-wrap:break-word"><ul style="box-sizing:border-box;padding-left:2em;margin-top:0px;margin-bottom:16px;color:rgb(36,41,46);font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Helvetica,Arial,sans-serif,"Apple Color Emoji","Segoe UI Emoji","Segoe UI Symbol";font-size:16px;background-color:rgb(255,255,255)"><li style="box-sizing:border-box;margin-top:0.25em">If you have used other languages or libraries with a similar feature, how do you feel that this proposal compares to those?</li></ul></div></blockquote><div>There is much more friction to using pointers in Swift than in C. However, making Swift pointers like C pointers is clearly a non-goal. This proposal appropriate addresses major pain points to Swift-specific usages of pointers.</div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex"><div style="word-wrap:break-word"><ul style="box-sizing:border-box;padding-left:2em;margin-top:0px;margin-bottom:16px;color:rgb(36,41,46);font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Helvetica,Arial,sans-serif,"Apple Color Emoji","Segoe UI Emoji","Segoe UI Symbol";font-size:16px;background-color:rgb(255,255,255)"><li style="box-sizing:border-box;margin-top:0.25em">How much effort did you put into your review? A glance, a quick reading, or an in-depth study?</li></ul></div></blockquote><div>A moderately thorough reading, drawing on some experience using pointer APIs in Swift, and based on prior readings of previous iterations of this proposal and the on-list discussion.</div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex"><div style="word-wrap:break-word"><p style="box-sizing:border-box;margin-top:0px;margin-bottom:16px;color:rgb(36,41,46);font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Helvetica,Arial,sans-serif,"Apple Color Emoji","Segoe UI Emoji","Segoe UI Symbol";font-size:16px;background-color:rgb(255,255,255)">More information about the Swift evolution process is available at</p><blockquote style="box-sizing:border-box;margin:0px 0px 16px;padding:0px 1em;color:rgb(106,115,125);border-left-width:0.25em;border-left-style:solid;border-left-color:rgb(223,226,229);font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Helvetica,Arial,sans-serif,"Apple Color Emoji","Segoe UI Emoji","Segoe UI Symbol";font-size:16px;background-color:rgb(255,255,255)"><div style="box-sizing:border-box;margin-top:0px;margin-bottom:0px"><a href="https://github.com/apple/swift-evolution/blob/master/process.md" style="box-sizing:border-box;background-color:transparent;color:rgb(3,102,214);text-decoration:none" target="_blank">https://github.com/apple/<wbr>swift-evolution/blob/master/<wbr>process.md</a></div></blockquote><p style="box-sizing:border-box;margin-top:0px;margin-bottom:16px;color:rgb(36,41,46);font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Helvetica,Arial,sans-serif,"Apple Color Emoji","Segoe UI Emoji","Segoe UI Symbol";font-size:16px;background-color:rgb(255,255,255)">Thank you,</p><p style="box-sizing:border-box;margin-top:0px;margin-bottom:16px;color:rgb(36,41,46);font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Helvetica,Arial,sans-serif,"Apple Color Emoji","Segoe UI Emoji","Segoe UI Symbol";font-size:16px;background-color:rgb(255,255,255)">-Doug</p><p style="box-sizing:border-box;margin-top:0px;margin-bottom:16px;color:rgb(36,41,46);font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Helvetica,Arial,sans-serif,"Apple Color Emoji","Segoe UI Emoji","Segoe UI Symbol";font-size:16px;background-color:rgb(255,255,255)">Review Manager</p></div><br>______________________________<wbr>_________________<br>
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