<div dir="ltr">You can add generic closures with some name mangling and simple transformations, nothing very hard.<div><br></div><div>The compiler can emit the following for example:</div><div><br></div><blockquote style="margin:0 0 0 40px;border:none;padding:0px">// User writes<br>let increment: <T: Numeric>(T) -> T = { $0 + 1 }<br>increment(1) // 2<br>increment(1.1) // 2.1<br><br><br>// Compiler issues<br>struct _Generic_Increment<T: Numeric> { // Mangle name<br> let increment: (T) -> T = { $0 + 1 }<br>}<br>_Generic_Increment<Int>().increment(1) // 2<br>_Generic_Increment<Double>().increment(1.1) // 2.1<br></blockquote><br><div>It's plausible that the compiler can do better than the above, but the above would be sufficient and is easy to do.</div></div><div class="gmail_extra"><br clear="all"><div><div class="gmail_signature" data-smartmail="gmail_signature"> -- Howard.<br></div></div>
<br><div class="gmail_quote">On 15 November 2017 at 14:02, Matthew Johnson <span dir="ltr"><<a href="mailto:matthew@anandabits.com" target="_blank">matthew@anandabits.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="auto"><br><br><div id="m_261741036942948137AppleMailSignature">Sent from my iPhone</div><div><br>On Nov 14, 2017, at 6:56 PM, Howard Lovatt via swift-evolution <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>> wrote:<br><br></div><blockquote type="cite"><div><div dir="ltr">Having read all the arguments for what to add to local functions it still strikes me as a poor use of engineering resources to fix them (though I do agree they have problems). A better use of resources would be:<div><br></div><div> 1. Deprecate local functions.</div><div> 2. Allow closures when assigned to a function type to be:</div><div> 2a. Recursive.</div><div> 2b. Annotatable with:</div><div> 2bi. @inline</div><div> 2bii. @escaping</div><div> 2c. Generic.</div><div><br></div><div>That would be a similar engineering effort and give a better short term result of better closures which would be much more widely applicable as well as addressing the issues with local functions.</div></div></div></blockquote><div><br></div>I believe generic closures would require adding higher rank types to Swift. That would be pretty cool but I suspect the engineering effort is at least an order of magnitude greater than the changes discussed in this thread.<div><br><blockquote type="cite"><div><div dir="ltr"><div><br></div><div>It also gives a better long term result of not having to maintain local functions.</div><div> </div></div><div class="gmail_extra"><br clear="all"><div><div class="m_261741036942948137gmail_signature" data-smartmail="gmail_signature"> -- Howard.<br></div></div>
<br><div class="gmail_quote">On 15 November 2017 at 09:08, Alex Lynch via swift-evolution <span dir="ltr"><<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">The inference algebra just suggested was enjoyable to read, but is still a new syntax. Which is interesting and deserving of its own proposal. The purpose of this proposal is simply to introduce the existing capture syntax to local functions. Thanks to everyone's feedback pointing out that the `self` reference analysis is a deeper question than initially realized. <div><br></div><div>Alex</div></div><div class="gmail_extra"><br><div class="gmail_quote"><div><div class="m_261741036942948137h5">On Tue, Nov 14, 2017 at 4:36 PM, Mike Kluev via swift-evolution <span dir="ltr"><<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>></span> wrote:<br></div></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div class="m_261741036942948137h5"><div dir="ltr"><span>On 14 November 2017 at 21:02, David Hart <span dir="ltr"><<a href="mailto:david@hartbit.com" target="_blank">david@hartbit.com</a>></span> wrote:<br></span><div class="gmail_extra"><div class="gmail_quote"><span><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex"><div style="word-wrap:break-word;line-break:after-white-space"><br><div><span class="m_261741036942948137m_6043367993829337200m_-5026886634801406416gmail-"><div><br></div></span>I’d be very hesitant to introduce this syntax:</div><div><br></div><div><ul class="m_261741036942948137m_6043367993829337200m_-5026886634801406416gmail-m_2863118398544756606MailOutline"><li>it’s new syntax, so it comes with a complexity tax (it isn’t naturally obvious what it means for a func to be weak)</li><li>it’s only sugar for the capture of self</li></ul></div></div></blockquote></span><div>it might cover well over 90% of use cases (by my "pessimistic" estimate)... if someone has a quick way to scan and analyse, say, github swift sources we may even know that current percentage number of real life usage.</div><span><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex"><div style="word-wrap:break-word;line-break:after-white-space"><div><ul class="m_261741036942948137m_6043367993829337200m_-5026886634801406416gmail-m_2863118398544756606MailOutline"><li>it doesn’t transpose well to local closures</li></ul></div></div></blockquote><div><br></div></span><div>the last one - maybe not. follow me:</div><div><br></div><div>let closure = { [weak self, bar] in ... }</div><div><br></div><div>which today can be written as: <br></div><div><br></div><div>let closure = { [weak self, bar] () -> Int in ... } // full form</div><div><br></div><div>or as:</div><div><br></div><div><div>let closure: () -> Int = { [weak self, bar] in ... } // full form</div></div><div><br></div><div><div>which allows this change:<br></div></div><div><br></div><div>let closure: [weak self, bar] () -> Int = { ... } // full alt form</div><div><br></div><div>or in alternative form:</div><div><br></div><div><div>let closure: weak () -> Int = { [bar] in ... } // short hand form</div></div><div><br></div><div>same can be with functions:</div><div><br></div><div>func fn() -> Int { [weak self, bar] in ... } // full form</div><div><br></div><div>weak func fn() -> Int { [bar] in ... } // short hand form</div><div><br></div><div>the two capture attributes will in practice be "close" to each other:</div><div><br></div><div><div>weak func fn() {</div><div> [bar] in</div><div> ....</div><div>}</div></div><div><br></div><div>and in majority of cases there will be only weak self:</div><div><br></div><div><div>weak func fn() {</div><div> ....<br></div><div>}</div></div><div><br></div><div>Mike</div><div><br></div></div></div></div>
<br></div></div><span>______________________________<wbr>_________________<br>
swift-evolution mailing list<br>
<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a><br>
<a href="https://lists.swift.org/mailman/listinfo/swift-evolution" rel="noreferrer" target="_blank">https://lists.swift.org/mailma<wbr>n/listinfo/swift-evolution</a><br>
<br></span></blockquote></div><br></div>
<br>______________________________<wbr>_________________<br>
swift-evolution mailing list<br>
<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a><br>
<a href="https://lists.swift.org/mailman/listinfo/swift-evolution" rel="noreferrer" target="_blank">https://lists.swift.org/mailma<wbr>n/listinfo/swift-evolution</a><br>
<br></blockquote></div><br></div>
</div></blockquote><blockquote type="cite"><div><span>______________________________<wbr>_________________</span><br><span>swift-evolution mailing list</span><br><span><a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a></span><br><span><a href="https://lists.swift.org/mailman/listinfo/swift-evolution" target="_blank">https://lists.swift.org/<wbr>mailman/listinfo/swift-<wbr>evolution</a></span><br></div></blockquote></div></div></blockquote></div><br></div>