<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="">An algorithm (as far as I know) is not inherently mutable. It is a process of apply a certain process (or a certain function) over and over again until you have a result. <div class=""><br class=""></div><div class="">If you processed it in writing (the common form of computing at the time) - you would write line after line of the results until you could break it down no farther (GCD).</div><div class=""><br class=""></div><div class="">Each step clearly documented, clearly written down (not erasing a value and inserting a new value). <br class=""><div class=""><br class=""></div><div class="">Basically you are applying a function on smaller and smaller bits (recursion) and recursion is not a mutable concept.</div><div class=""><br class=""></div><div class="">But I think that is more than enough digression :p</div><div class=""><br class=""><div><blockquote type="cite" class=""><div class="">On 2016-02-13, at 5:21:46, Dave Abrahams 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=""><br 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=""><span 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; float: none; display: inline !important;" class="">on Fri Feb 12 2016, Craig Cruden <</span><a href="mailto:swift-evolution@swift.org" 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="">swift-evolution@swift.org</a><span 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; float: none; display: inline !important;" class="">> wrote:</span><br 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=""><br 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" 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="">Not to mention - mutating (in my limited and aged math knowledge) is<br class="">NOT mathematical (computer simulations might use math in simulations<br class="">which simulating something that mutates)<br class=""><br class="">Mathematicians (typically) don’t mutate - they might be mutants…. but<br class="">they don’t mutate their equations.<br class=""><br class="">When was the last time you saw a mutating equation? If equations<br class="">mutate then it makes it much more difficult to prove correctness.<br class=""><br class="">Probably why even OO programming languages don’t allow you to mutate<br class="">an Integer or Decimal ….. bad things can happen.<br class=""><br class="">Union and intersection have more in common with operations like + and<br class="">- which also do not mutate the values.<br class=""></blockquote><br 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=""><span 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; float: none; display: inline !important;" class="">Let's not go too far with this. Euclid invented the GCD algorithm,</span><br 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=""><span 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; float: none; display: inline !important;" class="">which was originally expressed iteratively and therefore can be seen to</span><br 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=""><span 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; float: none; display: inline !important;" class="">be mutating variables. The whole concept of “algorithm” was named after</span><br 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=""><span 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; float: none; display: inline !important;" class="">an arabic mathematician.</span><br 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=""><br 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" 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=""><br class="">:p<br class=""><br class=""><blockquote type="cite" class=""><blockquote type="cite" class="">Reasoning:<br class=""><br class="">* I think the -ing endings sound unnatural, stilted, and unmathematical. They make me wince.<br class="">* I think you have the nature of the words mis-assigned. In my<br class="">opinion in this rare case, union, intersection, and exclusiveOr act<br class="">as verbs as they are mathematical set operations. For example,<br class="">"what is the result of A union B?" is a reasonable thing to say to<br class="">a math person or put on an exam question, etc.<br class=""></blockquote></blockquote><br class=""><blockquote type="cite" class=""><br class=""></blockquote><br class=""><blockquote type="cite" class="">On 2016-02-12, at 22:20:01, Thorsten Seitz via swift-evolution<br class=""><<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:<br class=""><br class="">I beg to disagree with your reasoning.<br class="">I think "union" is more commonly used as a noun and "intersection"<br class="">certainly is not a verb. Your example sounded weird for me (but<br class="">maybe that's because I'm not a native speaker) and I would rather<br class="">expect the question to be "What is the union of A and B?"<br class=""><br class="">-Thorsten<span class="Apple-converted-space"> </span><br class=""><br class="">Am 11.02.2016 um 20:09 schrieb Erica Sadun via swift-evolution<br class=""><<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a><br class=""><<a href="mailto:swift-evolution@swift.org" class="">mailto:swift-evolution@swift.org</a>>>:<br class=""><br class=""><blockquote type="cite" class="">My expectations is that the standard operators act upon a set, changing the set.<span class="Apple-converted-space"> </span><br class=""><br class="">set1.union(with: set2) tells set1 to perform the union.<span class="Apple-converted-space"> </span><br class="">set1.unioned(with: set2) creates a new instance where set1 has been unioned with set 2.<br class=""><br class="">Naming: intersected, unioned, and exclusiveOred over intersecting,<br class="">unioning, exclusiveOring.<br class="">Mutating: union, intersection, exclusiveOr.<span class="Apple-converted-space"> </span><br class="">Non-Mutating, returning new value: unioned(with), intersected(with), exclusiveOred(with)<br class=""><br class="">Reasoning:<br class=""><br class="">* I think the -ing endings sound unnatural, stilted, and unmathematical. They make me wince.<br class="">* I think you have the nature of the words mis-assigned. In my<br class="">opinion in this rare case, union, intersection, and exclusiveOr act<br class="">as verbs as they are mathematical set operations. For example,<br class="">"what is the result of A union B?" is a reasonable thing to say to<br class="">a math person or put on an exam question, etc.<br class=""><br class="">Importantly, they produce significant side effects, and should be<br class="">treated as verbs that operate upon the receiver, updating the<br class="">receiver, establishing their use for mutating ops.<br class=""><br class="">Dave wrote:<br class=""><blockquote type="cite" class=""><blockquote type="cite" class=""><blockquote type="cite" class="">- use nouns for methods with no side effects (or only incidental ones, like logging)<br class="">- use verbs for methods with significant side-effects<br class=""></blockquote></blockquote></blockquote><br class=""><br class="">-- E<br class=""><br class=""><blockquote type="cite" class="">On Feb 11, 2016, at 9:52 AM, Dave Abrahams via swift-evolution<br class=""><<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a><br class=""><<a href="mailto:swift-evolution@swift.org" class="">mailto:swift-evolution@swift.org</a>>><br class="">wrote:<br class=""><br class=""><br class="">Hi All,<br class=""><br class="">The API guidelines working group took up the issue of the InPlace suffix<br class="">yesterday, and decided that it was not to be used anywhere in the<br class="">standard library. We are planning to apply the changes shown here<br class=""><<a href="https://gist.github.com/dabrahams/d872556291a3cb797bd5" class="">https://gist.github.com/dabrahams/d872556291a3cb797bd5</a><br class=""><<a href="https://gist.github.com/dabrahams/d872556291a3cb797bd5" class="">https://gist.github.com/dabrahams/d872556291a3cb797bd5</a>>> to the<br class="">API of<br class="">SetAlgebra (and consequently Set) to make it conform to the guidelines<br class="">under development.<br class=""><br class="">Comments welcome as usual,<br class=""><br class="">--<span class="Apple-converted-space"> </span><br class="">-Dave<br class=""><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="mailto:swift-evolution@swift.org" class="">mailto: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=""><<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="mailto:swift-evolution@swift.org" class="">mailto: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=""><<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="">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 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=""><span 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; float: none; display: inline !important;" class="">--<span class="Apple-converted-space"> </span></span><br 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=""><span style="font-family: Helvetica; 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