<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">I haven’t read through the complete proposal in detail, but regarding the ‘scan’ operation I would like to point out that the definition given in the example matches the semantics of what is usually called ‘prescan' or 'exclusive scan', whereas ‘scan’ (aka ‘inclusive scan’ or ‘prefix sum’) would not include the identity element, and each position of the result would include applying the operator to the elements up to and including the element in the same position of the source array, e.g.:<div class=""><br class=""></div><div class=""> <span style="color: rgb(150, 152, 150); font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; background-color: rgb(247, 247, 247);" class="">(1..<6).scan(combine: +) // [1, 3, 6, 10, 15, 21]</span></div><div class=""><br class=""></div><div class="">Sources:</div><div class=""> <a href="https://www.cs.cmu.edu/~guyb/papers/Ble93.pdf" class="">https://www.cs.cmu.edu/~guyb/papers/Ble93.pdf</a></div><div class=""> <a href="https://en.wikipedia.org/wiki/Prefix_sum" class="">https://en.wikipedia.org/wiki/Prefix_sum</a></div><div class=""><br class=""></div><div class="">Mark</div><div class=""><br class=""></div><div class=""><br class=""><div><blockquote type="cite" class=""><div class="">On Apr 28, 2016, at 11:11 AM, Chris Lattner <<a href="mailto:clattner@apple.com" class="">clattner@apple.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class="">Hello Swift community,<br class=""><br class="">The review of "SE-0045: Add scan, prefix(while:), drop(while:), and iterate to the stdlib" begins now and runs through May 3. The proposal is available here:<br class=""><br class=""><span class="Apple-tab-span" style="white-space:pre"> </span><a href="https://github.com/apple/swift-evolution/blob/master/proposals/0045-scan-takewhile-dropwhile.md" class="">https://github.com/apple/swift-evolution/blob/master/proposals/0045-scan-takewhile-dropwhile.md</a><br class=""><br class="">Reviews are an important part of the Swift evolution process. All reviews should be sent to the swift-evolution mailing list at<br class=""><br class=""><span class="Apple-tab-span" style="white-space:pre"> </span>https://lists.swift.org/mailman/listinfo/swift-evolution<br class=""><br class="">or, if you would like to keep your feedback private, directly to the review manager.<br class=""><br class="">What goes into a review?<br class=""><br class="">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:<br class=""><br class=""><span class="Apple-tab-span" style="white-space:pre"> </span>* What is your evaluation of the proposal?<br class=""><span class="Apple-tab-span" style="white-space:pre"> </span>* Is the problem being addressed significant enough to warrant a change to Swift?<br class=""><span class="Apple-tab-span" style="white-space:pre"> </span>* Does this proposal fit well with the feel and direction of Swift?<br class=""><span class="Apple-tab-span" style="white-space:pre"> </span>* If you have you used other languages or libraries with a similar feature, how do you feel that this proposal compares to those?<br class=""><span class="Apple-tab-span" style="white-space:pre"> </span>* How much effort did you put into your review? A glance, a quick reading, or an in-depth study?<br class=""><br class="">More information about the Swift evolution process is available at<br class=""><br class=""><span class="Apple-tab-span" style="white-space:pre"> </span>https://github.com/apple/swift-evolution/blob/master/process.md<br class=""><br class="">Thank you,<br class=""><br class="">-Chris Lattner<br class="">Review Manager<br class=""><br class=""><br class="">_______________________________________________<br class="">swift-evolution-announce mailing list<br class="">swift-evolution-announce@swift.org<br class="">https://lists.swift.org/mailman/listinfo/swift-evolution-announce<br class=""></div></div></blockquote></div><br class=""></div></body></html>