<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div></div><div>It's been suggested by a core team member that enumerated itself might not hold its weight in the standard library. Instead, we ought to write `zip(foo.indices, foo)` or `zip(0..., foo)`. It's easier for the caller to see which side of the tuple stores the index and whether the index is an integer or an actual index type. This use case seems to further support this design since `zip(x…, foo)` and `zip(foo.indicies.drop(x), foo)` can be easily written.</div><div><br>On May 4, 2017, at 8:50 AM, BJ Homer via swift-evolution <<a href="mailto:swift-evolution@swift.org">swift-evolution@swift.org</a>> wrote:<br><br></div><blockquote type="cite"><div><meta http-equiv="Content-Type" content="text/html charset=utf-8">On May 4, 2017, at 8:51 AM, André Videla via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:<br class=""><div><blockquote type="cite" class=""><br class="Apple-interchange-newline"><div class=""><meta http-equiv="content-type" content="text/html; charset=utf-8" class=""><div dir="auto" class=""><div class="">You can do this trivially with drop. But enumerated from has one nice property:</div><div class=""><br class=""></div><div class="">myArray.enumerated().dropFirst(6) // counts from 6</div><div class=""><br class=""></div><div class="">myArray.dropFirst(6).enumerated() // counts from 0</div><div class=""><br class=""></div><div class="">Those two lines do very different things even though they look similar</div></div></div></blockquote></div><br class=""><div class="">Neither of those does what the proposed <font face="Menlo" class="">enumerated(from:)</font> does, if I understand correctly:</div><div class=""><br class=""></div><blockquote style="margin: 0 0 0 40px; border: none; padding: 0px;" class=""><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><div style="margin: 0px; line-height: normal;" class=""><div style="margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">let</span><span style="font-variant-ligatures: no-common-ligatures" class=""> a = [</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: #272ad8" class="">4</span><span style="font-variant-ligatures: no-common-ligatures" class="">, </span><span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">5</span><span style="font-variant-ligatures: no-common-ligatures" class="">]</span></div><div style="margin: 0px; line-height: normal; color: rgb(62, 30, 129);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">let</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""> result = </span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">a</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">.</span><span style="font-variant-ligatures: no-common-ligatures" class="">enumerated</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">().</span><span style="font-variant-ligatures: no-common-ligatures" class="">dropFirst</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">(</span><span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">2</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">)</span></div><div style="margin: 0px; line-height: normal; color: rgb(0, 132, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">/*</span></div><div style="margin: 0px; line-height: normal; color: rgb(0, 132, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> (offset: 2, element: 3)</span></div><div style="margin: 0px; line-height: normal; color: rgb(0, 132, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> (offset: 3, element: 4)</span></div><div style="margin: 0px; line-height: normal; color: rgb(0, 132, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> (offset: 4, element: 5)</span></div><div style="margin: 0px; line-height: normal; color: rgb(0, 132, 0); min-height: 13px;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""></span><br class=""></div><div style="margin: 0px; line-height: normal; color: rgb(0, 132, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> */</span></div><div style="margin: 0px; line-height: normal; min-height: 13px;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""></span><br class=""></div><div style="margin: 0px; line-height: normal; color: rgb(62, 30, 129);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">let</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""> result2 = </span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">a</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">.</span><span style="font-variant-ligatures: no-common-ligatures" class="">dropFirst</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">(</span><span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">2</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">).</span><span style="font-variant-ligatures: no-common-ligatures" class="">enumerated</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">()</span></div><div style="margin: 0px; line-height: normal; color: rgb(0, 132, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">/*</span></div><div style="margin: 0px; line-height: normal; color: rgb(0, 132, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> (offset: 0, element: 3)</span></div><div style="margin: 0px; line-height: normal; color: rgb(0, 132, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> (offset: 1, element: 4)</span></div><div style="margin: 0px; line-height: normal; color: rgb(0, 132, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> (offset: 2, element: 5)</span></div><div style="margin: 0px; line-height: normal; color: rgb(0, 132, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> */</span></div><div style="margin: 0px; line-height: normal; min-height: 13px;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""></span><br class=""></div><div style="margin: 0px; line-height: normal; min-height: 13px;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""></span><br class=""></div><div style="margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">let</span><span style="font-variant-ligatures: no-common-ligatures" class=""> proposed = </span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">a</span><span style="font-variant-ligatures: no-common-ligatures" class="">.enumerated(from: </span><span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">2</span><span style="font-variant-ligatures: no-common-ligatures" class="">)</span></div><div style="margin: 0px; line-height: normal; color: rgb(0, 132, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">/*</span></div><div style="margin: 0px; line-height: normal; color: rgb(0, 132, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> (offset: 2, element: 1)</span></div><div style="margin: 0px; line-height: normal; color: rgb(0, 132, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> (offset: 3, element: 2)</span></div><div style="margin: 0px; line-height: normal; color: rgb(0, 132, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> (offset: 4, element: 3)</span></div><div style="margin: 0px; line-height: normal; color: rgb(0, 132, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> (offset: 5, element: 4)</span></div><div style="margin: 0px; line-height: normal; color: rgb(0, 132, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> (offset: 6, element: 5)</span></div><div style="margin: 0px; line-height: normal; color: rgb(0, 132, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> */</span></div></div></div></blockquote><div class=""><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; min-height: 13px;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""></span></div></div><div class=""><div style="margin: 0px; line-height: normal; min-height: 13px;" class="">The <font face="Menlo" class="">enumerated(from:)</font> name is not clear; it reads (to me) like it’s going to enumerate elements starting at the Nth element. What it actually does (as proposed) is start counting at N, instead of counting at 0. <br class=""><br class=""><font face="Menlo" class=""><span style="font-variant-ligatures: no-common-ligatures; font-size: 11px;" class=""></span></font></div></div><div style="margin: 0px; line-height: normal; min-height: 13px;" class="">I’m not convinced this is a valuable addition to the language. The use cases are not widely applicable, and if you need it it’s easy to get the same results in a way that avoids the confusion.</div><div style="margin: 0px; line-height: normal; min-height: 13px;" class=""><br class=""></div><blockquote style="margin: 0 0 0 40px; border: none; padding: 0px;" class=""><div style="margin: 0px; line-height: normal; min-height: 13px;" class=""><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">let</span><span style="font-variant-ligatures: no-common-ligatures" class=""> a = [</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: #272ad8" class="">4</span><span style="font-variant-ligatures: no-common-ligatures" class="">, </span><span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">5</span><span style="font-variant-ligatures: no-common-ligatures" class="">]</span></div></div><div style="margin: 0px; line-height: normal; min-height: 13px;" class=""><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; min-height: 13px;" class=""><br class=""></div></div><div style="margin: 0px; line-height: normal; min-height: 13px;" class=""><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">let</span><span style="font-variant-ligatures: no-common-ligatures" class=""> result = </span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">a</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><span style="font-variant-ligatures: no-common-ligatures; color: #3e1e81" class="">map</span><span style="font-variant-ligatures: no-common-ligatures" class=""> { (idx, element) </span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">in</span></div></div><div style="margin: 0px; line-height: normal; min-height: 13px;" class=""><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">return</span><span style="font-variant-ligatures: no-common-ligatures" class=""> (idx+</span><span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">2</span><span style="font-variant-ligatures: no-common-ligatures" class="">, element)</span></div></div><div style="margin: 0px; line-height: normal; min-height: 13px;" class=""><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">}</span></div></div><div style="margin: 0px; line-height: normal; min-height: 13px;" class=""><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; min-height: 13px;" class=""><br class=""></div></div><div style="margin: 0px; line-height: normal; min-height: 13px;" class=""><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(0, 132, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">// OR</span></div></div><div style="margin: 0px; line-height: normal; min-height: 13px;" class=""><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; min-height: 13px;" class=""><br class=""></div></div><div style="margin: 0px; line-height: normal; min-height: 13px;" class=""><div style="margin: 0px; font-size: 11px; 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=""> (idx, element) </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: #4f8187" class="">a</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><div style="margin: 0px; line-height: normal; min-height: 13px;" class=""><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">let</span><span style="font-variant-ligatures: no-common-ligatures" class=""> offsetIndex = idx + </span><span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">2</span></div></div><div style="margin: 0px; line-height: normal; min-height: 13px;" class=""><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(0, 132, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""> </span><span style="font-variant-ligatures: no-common-ligatures" class="">// Use offsetIndex how you will</span></div></div><div style="margin: 0px; line-height: normal; min-height: 13px;" class=""><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">}</span></div></div></blockquote><div style="margin: 0px; line-height: normal; min-height: 13px;" class=""><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; min-height: 13px;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""><br class=""></span></div></div><div style="margin: 0px; line-height: normal; min-height: 13px;" class=""><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; min-height: 13px;" class=""><br class=""><span style="font-variant-ligatures: no-common-ligatures" class=""></span></div></div><div style="margin: 0px; line-height: normal; min-height: 13px;" class="">-BJ</div></div></blockquote><blockquote type="cite"><div><span>_______________________________________________</span><br><span>swift-evolution mailing list</span><br><span><a href="mailto:swift-evolution@swift.org">swift-evolution@swift.org</a></span><br><span><a href="https://lists.swift.org/mailman/listinfo/swift-evolution">https://lists.swift.org/mailman/listinfo/swift-evolution</a></span><br></div></blockquote></body></html>