<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div></div><div><br></div><div>Am 23.04.2016 um 10:27 schrieb Pyry Jahkola via swift-evolution <<a href="mailto:swift-evolution@swift.org">swift-evolution@swift.org</a>>:<br><br></div><blockquote type="cite"><div><meta http-equiv="Content-Type" content="text/html charset=utf-8"><div class="">I'd like to second James Campbell's suggestion of a `<font face="Menlo" class=""><span style="font-size: 11px;" class="">mutate</span></font>` keyword. Clarifying comments inline below:</div><br class=""><blockquote type="cite" class="">On 23 Apr 2016, at 00:24, Dave Abrahams via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:<br class=""></blockquote><div><blockquote type="cite" class=""><br class="Apple-interchange-newline"><div class=""><span style="font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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="">This is not a new idea. Something almost identical to this has been</span><br style="font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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="">explored and discussed quite thoroughly already:</span><br style="font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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><a href="https://github.com/apple/swift/blob/master/docs/proposals/Inplace.rst" style="font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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="">https://github.com/apple/swift/blob/master/docs/proposals/Inplace.rst</a><span style="font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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><br style="font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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="">In fact, it was implmented and later reverted because it raised</span><br style="font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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="">language-design questions for which we had no good answers.</span></div></blockquote><div><br class=""></div><div>I don't know if the following are particularly good answers, but I'll try anyway:</div><br class=""><blockquote type="cite" class=""><div class=""><span style="font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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="">I don't </span><span style="font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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="">believe the choice of glyph (& vs =) affects any of the</span></div></blockquote><blockquote type="cite" class=""><div class=""><span style="font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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="">fundamental </span><span style="font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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="">issues:</span><br style="font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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="">* Should the x.=f() syntax be required for *every* mutating method</span><br style="font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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=""> invocation?</span><br style="font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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=""></div></blockquote><div><br class=""></div><div>Allow me to ask it differently: Should <b class="">some</b> specific syntax be required for every mutating method? — Yes.</div></div></div></blockquote><div><br></div>I think I like that idea.<div><br></div><div><br><blockquote type="cite"><div><div>Should the syntax be `<font face="Menlo" class=""><span style="font-size: 11px;" class="">x.=f()</span></font>`? — Not necessarily. I kinda like James Campbell's idea of a `<font face="Menlo" class=""><span style="font-size: 11px;" class="">mutate</span></font>` keyword. Consider the following:</div><div><br class=""></div><div><font face="Menlo" class=""><span style="font-size: 11px;" class=""> <b class="">var</b> numbers = [5, 12, 6, 2]</span></font></div><div><font face="Menlo" class=""><span style="font-size: 11px;" class=""> <b class="">mutate</b> numbers.append(10)</span></font></div><div><font face="Menlo" class=""><span style="font-size: 11px;" class=""> <b class="">mutate</b> numbers.sort()</span></font></div><div><font face="Menlo" class=""><span style="font-size: 11px;" class=""> <b class="">if let</b> </span></font><span style="font-family: Menlo; font-size: 11px;" class="">biggest</span><font face="Menlo" class=""><span style="font-size: 11px;" class=""> = <b class="">mutate</b> numbers.popLast() {</span></font></div><div><font face="Menlo" class=""><span style="font-size: 11px;" class=""> print("The biggest number was:", biggest)</span></font></div><div><font face="Menlo" class=""><span style="font-size: 11px;" class=""> }</span></font></div><div><br class=""></div><div>So `<font face="Menlo" class=""><span style="font-size: 11px;" class="">mutate</span></font>` would work much like `<font face="Menlo" class=""><span style="font-size: 11px;" class="">try</span></font>` but—unlike `<font face="Menlo" class=""><span style="font-size: 11px;" class="">try</span></font>` which can move further to the left—`<font face="Menlo" class=""><span style="font-size: 11px;" class="">mutate</span></font>` would have to always prefix the mutating receiver. </div></div></blockquote><div><br></div><div>That doesn't look so bad (we might shorten 'mutate' to 'mut', though I don't think that would be really necessary).</div><div>I'm wondering how to deal with fluent interfaces which do mutate the receiver and return 'self', i.e. the builder pattern. I think we can simply require that such a chained expression is required to consist of only mutating calls (or only non-mutating calls), so that one 'mutate' for the whole expression would be sufficient.</div><div>Expressions combining mutating calls to different receivers which have return values would simply be prohibited. This would probably be bad style anyway (contrary to the fluent example), or does anyone have a good counter example?</div><div><br></div><br><blockquote type="cite"><div><div>Here's a contrived example of a corner case:</div><div><br class=""></div><div><font face="Menlo" class=""><span style="font-size: 11px;" class=""> <b class="">enum</b> Error : ErrorType { <b class="">case</b> BadNumber }</span></font></div><div><font face="Menlo" class=""><span style="font-size: 11px;" class=""><br class=""></span></font></div><div><font face="Menlo" class=""><span style="font-size: 11px;" class=""> <b class="">func</b> demo() <b class="">throws</b> -> Int {</span></font></div><div><font face="Menlo" class=""><span style="font-size: 11px;" class=""> </span></font></div><div><font face="Menlo" class=""><span style="font-size: 11px;" class=""> }</span></font></div><div><br class=""></div><blockquote type="cite" class=""><div class=""><span style="font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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="">* Are assignment methods a redundant way to spell mutating methods?</span><br style="font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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=""> Should we really have both mechanisms?</span></div></blockquote><div><br class=""></div><div>(I had to look up the definition of an <i class="">assignment method</i>. For the uninitiated, Dave is talking about what's written here: <a href="https://github.com/apple/swift/blob/master/docs/proposals/Inplace.rst#use-one-simple-name" class="">https://github.com/apple/swift/blob/master/docs/proposals/Inplace.rst#use-one-simple-name</a>.)</div><div><br class=""></div><div>— Yes they are redundant, and no, we should not have both.</div><div><br class=""></div><div>With `<font face="Menlo" class=""><span style="font-size: 11px;" class="">mutate</span></font>` required at the call site, we could simply allow both overloads `<font face="Menlo" class=""><span style="font-size: 11px;" class=""><b class="">func</b> sort()</span></font>` and `<font face="Menlo" class=""><span style="font-size: 11px;" class=""><b class="">mutating func</b> sort()</span></font>` to coexist, because the call sites become unambiguous:</div><div><br class=""></div><div><font face="Menlo" class=""><span style="font-size: 11px;" class=""> <b class="">let</b> originals = [2, 1, 3, 0, 4, 2]</span></font></div><div><font face="Menlo" class=""><span style="font-size: 11px;" class=""> <b class="">var</b> copies = originals</span></font></div><div><font face="Menlo" class=""><span style="font-size: 11px;" class=""><br class=""></span></font></div><div><font face="Menlo" class=""><span style="font-size: 11px;" class=""> originals.sort() <font color="#919191" class="">// <b class="">warning:</b> result of call to 'sort()' is unused</font></span></font></div><div><font face="Menlo" class=""><span style="font-size: 11px;" class=""> <font color="#ff2600" class=""><b class="">mutate</b> originals.sort()</font> <font color="#919191" class="">// <b class="">compiler error</b></font></span></font></div><div><font face="Menlo" class=""><span style="font-size: 11px;" class=""> <b class="">let</b> xs = originals.sort() <font color="#919191" class="">// ok</font></span></font></div><div><br class=""></div><div><font face="Menlo" class=""><span style="font-size: 11px;" class=""> copies.sort()</span></font><span style="font-family: Menlo; font-size: 11px;" class=""> </span><span style="font-family: Menlo; font-size: 11px;" class=""><font color="#919191" class="">// <b class="">warning:</b> result of call to 'sort()' is unused</font></span></div><div><font face="Menlo" class=""><span style="font-size: 11px;" class=""> <b class="">mutate</b> copies.sort() <font color="#919191" class="">// ok</font></span></font></div><div><font face="Menlo" class=""><span style="font-size: 11px;" class=""> <b class="">let</b> ys = copies.sort() <font color="#919191" class="">// ok</font></span></font></div><div><span style="font-size: 11px; font-family: Menlo;" class=""> <b class="">let</b> zs = mutate copies.sort() <font color="#919191" class="">// <b class="">warning:</b> constant 'x' inferred to have type '()', which may be unexpected</font></span></div><div><br class=""></div><div>The language could also allow the use of</div><div><font face="Menlo" class=""><span style="font-size: 11px;" class=""><b class=""><br class=""></b></span></font></div><div><b style="font-family: Menlo; font-size: 11px;" class=""> mutate</b><font face="Menlo" class=""><span style="font-size: 11px;" class=""> x.next()</span></font></div><div><br class=""></div><div>as shorthand for</div><div><br class=""></div><div><font face="Menlo" class=""><span style="font-size: 11px;" class=""> x = x.next()</span></font></div><div><br class=""></div><div>when only the non-mutating variant `<font face="Menlo" class=""><span style="font-size: 11px;" class=""><b class="">func</b> next() -> <b class="">Self</b></span></font>` exists with compatible return type.</div><br class=""><blockquote type="cite" class=""><div class=""><span style="font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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="">* Can we really introduce this feature without having a way to apply it</span><br style="font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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=""> to class types?</span><br style="font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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=""></div></blockquote><div><br class=""></div><div>Yes we can. Why complicate the naming of value type members with the complexities of reference semantics? The current API naming conventions are <i class="">good</i> for reference types which sometimes come with unobvious to obscure behaviour (i.e. anything from bumping an internal counter to firing missiles and wiping hard drives).</div><div><br class=""></div><div>But value types ought to have no side effects (besides memory allocation and logging maybe), and so we don't necessarily need that strong a naming convention to limit their collateral damage.</div><div><br class=""></div><div>If the `<font face="Menlo" class=""><span style="font-size: 11px;" class="">mutate</span></font>` keyword became required for calling `<font face="Menlo" class=""><span style="font-size: 11px;" class="">mutating</span></font>` methods, then operators would remain the only place where naming convention were needed to distinguish mutation:</div><div><br class=""></div><div><ul class="MailOutline"><li class="">Mutating assignment is <b class="">explicit</b>: `<font face="Menlo" class=""><span style="font-size: 11px;" class="">xs = [1, 2] + xs + [2, 1]</span></font>` (i.e. `<font face="Menlo" class=""><span style="font-size: 11px;" class="">=</span></font>` without `<font face="Menlo" class=""><span style="font-size: 11px;" class="">let</span></font>` or `<font face="Menlo" class=""><span style="font-size: 11px;" class="">var</span></font>` means mutation)</li><li class="">Mutating method call becomes <b class="">explicit</b>: `<font face="Menlo" class=""><span style="font-size: 11px;" class=""><b class="">mutate</b> xs.sort()</span></font>` and `<font face="Menlo" class=""><span style="font-size: 11px;" class=""><b class="">let</b> x = <b class="">mutate</b> xs.removeAtIndex(2)</span></font>`</li><li class="">Mutating function arguments are <b class="">explicit</b> with the `<font face="Menlo" class=""><span style="font-size: 11px;" class="">&</span></font>` prefix: `<font face="Menlo" class=""><span style="font-size: 11px;" class="">swap(&xs, &ys)</span></font>`</li><li class="">Mutating operators are <b class="">implicit</b> and <i class="">by convention,</i> should end with the `=` symbol: `<font face="Menlo" class=""><span style="font-size: 11px;" class="">xs += [8, 9]</span></font>`</li><li class="">Reference types have no notion of `<font face="Menlo" class=""><span style="font-size: 11px;" class="">mutating</span></font>` members (and probably ought to remain that way) so they mutate <b class="">implicitly</b>.</li></ul></div><br class=""><blockquote type="cite" class=""><div class=""><span style="font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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="">I should also point out that under the assignment method paradigm one</span><br style="font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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="">would probably need to re-evalutate rules for naming. Under the current</span><br style="font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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="">API guidelines' approach, we'd write:</span><br style="font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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=""> x.=sorted() // sort x in-place</span><br style="font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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="">and I am not sure how easy that would be for people to swallow</span><br style="font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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="">considering how much more straightforward</span><br style="font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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=""> x.sort() // current way to sort x in-place</span><br style="font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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="">is, and because the language now contains explicit notation for</span><br style="font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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="">mutation, it becomes harder to argue against theis pair:</span><br style="font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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=""> y = x.sort()</span><br style="font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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=""> x.=sort() // sort x in place</span><br style="font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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=""></div></blockquote><div><br class=""></div><div>I agree that the current API guidelines wouldn't work for value types anymore. Both `sort` and `sorted` would be called `sort`.</div><br class=""><blockquote type="cite" class=""><div class=""><span style="font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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="">Lastly, I should point out that the proposal does nothing to solve the</span><br style="font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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="">problem of `c.formSuccessor(&i)`, since that doesn't mutate the</span><br style="font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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="">receiver.</span><br style="font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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=""></div></blockquote><div><br class=""></div><div>This proposal does address the problem of `<font face="Menlo" class=""><span style="font-size: 11px;" class="">c.formSuccessor(&i)</span></font>`. Given that it's value types at play here, what mutates in the following is unambiguous even to non-native English speakers:</div><div><br class=""></div><div><font face="Menlo" class=""><span style="font-size: 11px;" class=""> c.frobnicate(&i) <font color="#919191" class="">// cannot possibly mutate c but mutates i</font></span></font></div><div><font face="Menlo" class=""><span style="font-size: 11px;" class=""> </span><b style="font-size: 11px;" class="">let</b><span style="font-size: 11px;" class=""> j = c.frobnicate(i) </span><font color="#919191" style="font-size: 11px;" class="">// cannot possibly mutate either</font></font></div><div><font face="Menlo" class=""><span style="font-size: 11px;" class=""> </span><b style="font-size: 11px;" class="">mutate</b><span style="font-size: 11px;" class=""> c.frobnicate(i) </span><font color="#919191" style="font-size: 11px;" class="">// mutates c</font></font></div><div><font face="Menlo" class=""><span style="font-size: 11px;" class=""> </span><b style="font-size: 11px;" class="">let</b><span style="font-size: 11px;" class=""> k = </span><b style="font-size: 11px;" class="">mutate</b><span style="font-size: 11px;" class=""> c.frobnicate(&i) </span><font color="#919191" style="font-size: 11px;" class="">// mutates both</font></font></div></div></blockquote><div><br></div>That's really very straightforward.</div><div><br></div><div>As an alternative to the mutate keyword I rather like using '&' because it already means 'inout'. Using '&.' as mutating method call would therefore be quite understandable.</div><div><br></div><div>c&.frobnicate(i)</div><div>let k = c&.frobnicate(&i)</div><div><br></div><div>Or marking the method like suggested elsewhere:</div><div><br></div><div>c.frobnicate&(i)</div><div>let k = c.frobnicate&(&i)</div><div><br></div><div>-Thorsten </div><div><br></div><div><br></div><div><blockquote type="cite"><div><br class=""><blockquote type="cite" class=""><div class=""><span style="font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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="">I still like the proposal's basic approach and would love to see it used</span><br style="font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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="">to address these naming problems, but I want to be clear that it's by no</span><br style="font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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="">means a panacea and there are real obstacles between here and actually</span><br style="font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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="">being able to apply it. If you want to move forward with something like</span><br style="font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: 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="">this, you need to solve the problems described above.</span></div></blockquote></div><br class="">I think this proposal would simplify all code handling value types. Yes, it adds one keyword of boilerplate but wins clarity in return. I think reference types should stay separate from this discussion, as their mutation has always been implicit anyway. The API guidelines set a good convention for them.<br class=""><div class=""><br class=""></div><div class="">— Pyry</div><div class=""><br class=""></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></div></body></html>