<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><br class=""><div><blockquote type="cite" class=""><div class="">On Jan 31, 2017, at 3:24 PM, Chris Eidhof via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class="">Hey everyone,<div class=""><br class=""></div><div class="">I've organized a number of Swift workshops over the last two years. There are a couple of things that keep coming up, and a couple of mistakes that I see people making over and over again. One of them is that in almost every workshop, there's someone who thinks that `enumerated()` returns a list of (index, element) pairs. This is only true for arrays. It breaks when using array slices, or any other kind of collection. In our workshops, I sometimes see people doing something like `x.reversed().enumerated()`, where `x` is an array, and somehow it produces behavior they don't understand.</div></div></div></blockquote><div><br class=""></div><div>What is the behavior that you'd like?</div><div><br class=""></div><div><div style="margin: 0px; font-size: 9px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">for</span><span style="font-variant-ligatures: no-common-ligatures" class=""> x </span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">in</span><span style="font-variant-ligatures: no-common-ligatures" class=""> [</span><span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">1</span><span style="font-variant-ligatures: no-common-ligatures" class="">, </span><span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">2</span><span style="font-variant-ligatures: no-common-ligatures" class="">, </span><span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">3</span><span style="font-variant-ligatures: no-common-ligatures" class="">].</span><span style="font-variant-ligatures: no-common-ligatures; color: #3e1e81" class="">reversed</span><span style="font-variant-ligatures: no-common-ligatures" class="">().</span><span style="font-variant-ligatures: no-common-ligatures; color: #3e1e81" class="">enumerated</span><span style="font-variant-ligatures: no-common-ligatures" class="">() {</span></div><div style="margin: 0px; font-size: 9px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures;" class=""> <font color="#3e1e81" class="">print</font></span><span style="color: rgb(0, 0, 0); font-variant-ligatures: no-common-ligatures;" class="">(x)</span></div><div style="margin: 0px; font-size: 9px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">}</span></div></div><div><br class=""></div><div>produces (first column is the index, second the element):</div><div><br class=""></div><div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""><b class="">(0, 3)</b></span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""><b class="">(1, 2)</b></span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""><b class="">(2, 1)</b></span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><br class=""></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-family: Helvetica; font-size: 10px;" class="">- it IMHO behaves as one would expect - it returns an index into the sequence that you are enumerating...</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-family: Helvetica; font-size: 10px;" class=""><br class=""></span></div></div><blockquote type="cite" class=""><div class=""><div dir="ltr" class=""><div class=""><br class=""></div><div class="">A few ways I think this could be improved:</div><div class=""><br class=""></div><div class="">- Move enumerated to Array</div><div class="">- Change enumerated to return `(Index, Iterator.Element)` (this would mean we at least need to move it to collection)</div><div class="">- Remove enumerated</div><div class="">- Keep things as is</div><div class=""><br class=""></div><div class="">In any case, just wanted to share my experience (gained from teaching people). </div><div class=""><div class=""><br class=""></div>-- <br class=""><div class="gmail_signature" data-smartmail="gmail_signature">Chris Eidhof</div>
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