-1<br><br><div class="gmail_quote"><div dir="ltr">On Wed, Dec 28, 2016 at 9:37 AM Tony Allevato via swift-evolution <<a href="mailto:swift-evolution@swift.org">swift-evolution@swift.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr" class="gmail_msg">–1. I'm not sure there's a reason to draw a line from removal-of-tuple-splat to removal-of-tuple-returns, other than the idea that they both involve tuples. In a lot of languages, purely-"out" parameters are a workaround for the fact that the language wasn't designed to allow functions to return multiple values easily. Since Swift does allow this, eliminating and adding "out" params is a step *backward*, not a step forward.<div class="gmail_msg"><br class="gmail_msg"></div><div class="gmail_msg">"Inout" parameters at least serve an important role with respect to in-place mutability. "Out"-only parameters don't seem like something that would have much value in Swift.<br class="gmail_msg"><div class="gmail_msg"><br class="gmail_msg"></div><div class="gmail_msg">The syntactic distinction between inputs and outputs in Swift's function syntax is important to readability—I find the example given with "out" params to be considerably harder to parse mentally than the version that returns a tuple. From the point of view of making the language easy for newcomers to learn... replacing tuple returns with "out" parameters would be extremely harmful.</div></div></div><div dir="ltr" class="gmail_msg"><div class="gmail_msg"><div class="gmail_msg"><br class="gmail_msg"></div><div class="gmail_msg"><br class="gmail_msg"><div class="gmail_quote gmail_msg"><div dir="ltr" class="gmail_msg">On Wed, Dec 28, 2016 at 3:10 AM Anton Zhilin via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="gmail_msg" target="_blank">swift-evolution@swift.org</a>> wrote:<br class="gmail_msg"></div><blockquote class="gmail_quote gmail_msg" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr" class="gmail_msg"><div class="m_5854240714484172279m_7521060050161717650markdown-here-wrapper gmail_msg"><p style="margin:0px 0px 1.2em!important" class="gmail_msg">Some people on the list wondered, why we have moved from tuples in function parameters, but multiple returns are still implemented using tuples? The following code still compiles:</p>
<pre style="font-size:0.85em;font-family:Consolas,Inconsolata,Courier,monospace;font-size:1em;line-height:1.2em;margin:1.2em 0px" class="gmail_msg"><code class="m_5854240714484172279m_7521060050161717650hljs m_5854240714484172279m_7521060050161717650language-swift gmail_msg" style="font-size:0.85em;font-family:Consolas,Inconsolata,Courier,monospace;margin:0px 0.15em;padding:0px 0.3em;white-space:pre-wrap;border:1px solid rgb(234,234,234);background-color:rgb(248,248,248);border-radius:3px;display:inline;white-space:pre-wrap;overflow:auto;border-radius:3px;border:1px solid rgb(204,204,204);padding:0.5em 0.7em;display:block!important;display:block;overflow-x:auto;padding:0.5em;color:rgb(51,51,51);background:rgb(248,248,248)"><span class="m_5854240714484172279m_7521060050161717650hljs-func gmail_msg"><span class="m_5854240714484172279m_7521060050161717650hljs-keyword gmail_msg" style="color:rgb(51,51,51);font-weight:bold">func</span> <span class="m_5854240714484172279m_7521060050161717650hljs-title gmail_msg" style="color:rgb(153,0,0);font-weight:bold">position</span><span class="m_5854240714484172279m_7521060050161717650hljs-params gmail_msg">()</span> -> <span class="m_5854240714484172279m_7521060050161717650hljs-params gmail_msg">(x: Int, y: Int)</span> </span>{
<span class="m_5854240714484172279m_7521060050161717650hljs-keyword gmail_msg" style="color:rgb(51,51,51);font-weight:bold">return</span> (x: <span class="m_5854240714484172279m_7521060050161717650hljs-number gmail_msg" style="color:rgb(0,128,128)">0</span>, y: <span class="m_5854240714484172279m_7521060050161717650hljs-number gmail_msg" style="color:rgb(0,128,128)">0</span>)
}
<span class="m_5854240714484172279m_7521060050161717650hljs-keyword gmail_msg" style="color:rgb(51,51,51);font-weight:bold">let</span> (y, x) = position()
</code></pre>
<p style="margin:0px 0px 1.2em!important" class="gmail_msg">(Maybe it’s a bad example, because naturally we’d use <code style="font-size:0.85em;font-family:Consolas,Inconsolata,Courier,monospace;margin:0px 0.15em;padding:0px 0.3em;white-space:pre-wrap;border:1px solid rgb(234,234,234);background-color:rgb(248,248,248);border-radius:3px;display:inline" class="gmail_msg">Point</code> struct. Let’s pretend those two parameters don’t make sense as a struct.)</p>
<p style="margin:0px 0px 1.2em!important" class="gmail_msg">What I want to discuss is if we should introduce <code style="font-size:0.85em;font-family:Consolas,Inconsolata,Courier,monospace;margin:0px 0.15em;padding:0px 0.3em;white-space:pre-wrap;border:1px solid rgb(234,234,234);background-color:rgb(248,248,248);border-radius:3px;display:inline" class="gmail_msg">out</code> parameters <strong class="gmail_msg">and</strong> make them the default for multiple returns for Swift 4. The syntax would look like:</p>
<pre style="font-size:0.85em;font-family:Consolas,Inconsolata,Courier,monospace;font-size:1em;line-height:1.2em;margin:1.2em 0px" class="gmail_msg"><code class="m_5854240714484172279m_7521060050161717650hljs m_5854240714484172279m_7521060050161717650language-swift gmail_msg" style="font-size:0.85em;font-family:Consolas,Inconsolata,Courier,monospace;margin:0px 0.15em;padding:0px 0.3em;white-space:pre-wrap;border:1px solid rgb(234,234,234);background-color:rgb(248,248,248);border-radius:3px;display:inline;white-space:pre-wrap;overflow:auto;border-radius:3px;border:1px solid rgb(204,204,204);padding:0.5em 0.7em;display:block!important;display:block;overflow-x:auto;padding:0.5em;color:rgb(51,51,51);background:rgb(248,248,248)"><span class="m_5854240714484172279m_7521060050161717650hljs-func gmail_msg"><span class="m_5854240714484172279m_7521060050161717650hljs-keyword gmail_msg" style="color:rgb(51,51,51);font-weight:bold">func</span> <span class="m_5854240714484172279m_7521060050161717650hljs-title gmail_msg" style="color:rgb(153,0,0);font-weight:bold">position</span><span class="m_5854240714484172279m_7521060050161717650hljs-params gmail_msg">(x: out Int, y: out Int)</span> </span>{
x = <span class="m_5854240714484172279m_7521060050161717650hljs-number gmail_msg" style="color:rgb(0,128,128)">0</span>
y = <span class="m_5854240714484172279m_7521060050161717650hljs-number gmail_msg" style="color:rgb(0,128,128)">0</span>
}
<span class="m_5854240714484172279m_7521060050161717650hljs-keyword gmail_msg" style="color:rgb(51,51,51);font-weight:bold">var</span> y
position(x: <span class="m_5854240714484172279m_7521060050161717650hljs-keyword gmail_msg" style="color:rgb(51,51,51);font-weight:bold">let</span> x, y: y)
</code></pre>
<p style="margin:0px 0px 1.2em!important" class="gmail_msg"><code style="font-size:0.85em;font-family:Consolas,Inconsolata,Courier,monospace;margin:0px 0.15em;padding:0px 0.3em;white-space:pre-wrap;border:1px solid rgb(234,234,234);background-color:rgb(248,248,248);border-radius:3px;display:inline" class="gmail_msg">out</code> arguments can be any patterns allowed on the left side of assignment, including wildcard pattern and tuple destructuring pattern.</p>
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