<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="">Just to add to that, it’s always seemed strange to me that to signify your sequence is multi-pass (i.e., to make it conform to CollectionType) you have to have it conform to Indexable. <div class=""><br class=""><div><blockquote type="cite" class=""><div class="">On 31 Dec 2015, at 17:52, Erica Sadun 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 class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;">I'm trying to work them out, so it's still muddled.</div><div class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><br class=""></div><div class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;">Right now, I think<span class="Apple-converted-space"> </span><font face="Menlo" class="">SequenceType</font><span class="Apple-converted-space"> </span>is better described as<span class="Apple-converted-space"> </span><font face="Menlo" class="">CollectionWalkType</font><span class="Apple-converted-space"> </span>but that's kind of (1) a mouthful and (2) not entirely accurate. </div><div class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><br class=""></div><div class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;">Moving back a step:<span class="Apple-converted-space"> </span><font face="Menlo" class="">SequenceType</font><span class="Apple-converted-space"> </span>is defined as: "A type that can be iterated with a `for`...`in` loop." But it says nothing about whether that loop ever terminates and many stdlib sequence functions currently don't make sense (at least if they're not lazy) with respect to infinite sequences, which should probably be "<font face="Menlo" class="">StreamType</font>" not sequences. A couple of examples:</div><div class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><ul class=""><li class="">Here's my fib: <a href="http://swiftstub.com/189513594/" class="">http://swiftstub.com/189513594/</a></li><li class="">And here's Oisin's user-input sequence: <a href="https://gist.github.com/oisdk/2c7ac33bf2188528842a" class="">https://gist.github.com/oisdk/2c7ac33bf2188528842a</a></li></ul></div><div class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;">Both of these are theoretically filterable, but they aren't dropLast-able, suffix-able, properly split-able, etc.</div><div class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><br class=""></div><div class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;">Hopefully that's enough of a starting point to indicate where my thinking is at and what I'm trying to think through when it comes to this. -- E</div><div class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><br class=""></div><br class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><div style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><blockquote type="cite" class=""><div class="">On Dec 31, 2015, at 10:09 AM, Dave Abrahams <<a href="mailto:dabrahams@apple.com" class="">dabrahams@apple.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class=""><br class=""><blockquote type="cite" class="">On Dec 31, 2015, at 9:05 AM, Erica Sadun via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:<br class=""><br class="">It does seem that in Swift the concepts of collection, sequence, permutation, stream, etc are a bit muddled.<br class=""></blockquote><br class="">This is a pretty vague critique. Do you have specifics, and suggestions that address them?<br class=""><br class=""><blockquote type="cite" class=""><br class="">-- E<br class=""><br class=""><br class=""><blockquote type="cite" class="">On Dec 31, 2015, at 6:51 AM, Tino Heth via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:<br class=""><br class=""><blockquote type="cite" class="">Those are collections. Collections can be iterated over multiple times.<br class=""></blockquote>Speaking of the Fibonacci-numbers:<br class="">Sure we can write an algorithm that iterates over them several times — it just won't ever finish the first iteration ;-)<br class="">(only nitpicking — I just couldn't resist)<br class=""><br class="">Happy new year!<br class="">_______________________________________________<br class="">swift-evolution mailing list<br class=""><a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a><br class=""><a href="https://lists.swift.org/mailman/listinfo/swift-evolution" class="">https://lists.swift.org/mailman/listinfo/swift-evolution</a><br class=""></blockquote><br class="">_______________________________________________<br class="">swift-evolution mailing list<br class=""><a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a><br class=""><a href="https://lists.swift.org/mailman/listinfo/swift-evolution" class="">https://lists.swift.org/mailman/listinfo/swift-evolution</a><br class=""></blockquote><br class="">-Dave<br class=""><br class=""></div></div></blockquote></div><br class="" style="font-family: Helvetica; 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