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.send { color:#77bb77; }
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.error { color:#AA0000; }</style></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><div class="bloop_markdown"><p>Thank you guys for all your suggestions so far.</p>
<p>I understand the idea behind the generic subscript here, they are neat and highly needed, but even this approach won’t solve my issue of clarity here.</p>
<p>The Array I extend here has an <code>Element</code> of type <code>Value</code> which is an enum that wraps other types around (part of BSON).</p>
<p>I’d have to insert a huge pattern matching switch into that generic subscript and unwrap every possible type. Don’t get me wrong, this would work, because the result type is an optional, where I just can return nil if nothing matches.</p>
<p>But again I lose the clarity from the readers prospective, because I don’t know by reading code like <code>array[at: 123] = someValue</code> what kind of subscript I’m using here. </p>
<p>As already suggested, the view workaround would result in the exact the same syntax I look for, but it has it own downsides as I already mentioned (+ every time you’d need to instantiate a new view).</p>
<p></p></div><div class="bloop_original_html"><style>body{font-family:Helvetica,Arial;font-size:13px}</style><div id="bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px; color: rgba(0,0,0,1.0); margin: 0px; line-height: auto;"><br></div> <br> <div id="bloop_sign_1479460311132606976" class="bloop_sign"><div style="font-family:helvetica,arial;font-size:13px">-- <br>Adrian Zubarev<br>Sent with Airmail</div></div> <br><p class="airmail_on">Am 18. November 2016 um 09:55:00, Haravikk (<a href="mailto:swift-evolution@haravikk.me">swift-evolution@haravikk.me</a>) schrieb:</p> <blockquote type="cite" class="clean_bq"><span><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div></div><div>
<title></title>
<div class="">Could this be addressed by allowing generic
constraints on subscripts?</div>
<div class="">For example, with methods we can currently do:</div>
<div class=""><br class=""></div>
<blockquote style="margin: 0 0 0 40px; border: none; padding: 0px;" class="">
<div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class="">
<div style="margin: 0px; line-height: normal;" class="">
<div style="margin: 0px; line-height: normal;" class="">
<span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">struct</span> <span style="font-variant-ligatures: no-common-ligatures" class="">Foo
{</span></div>
<div style="margin: 0px; line-height: normal;" class="">
<span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">var</span> <span style="font-variant-ligatures: no-common-ligatures" class="">values:[</span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">Any</span><span style="font-variant-ligatures: no-common-ligatures" class="">] =
[]</span></div>
<div style="margin: 0px; line-height: normal; min-height: 13px;" class=""><br class=""></div>
<div style="margin: 0px; line-height: normal;" class="">
<span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">func</span> <span style="font-variant-ligatures: no-common-ligatures" class="">get<T>(at:</span><span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">Int</span><span style="font-variant-ligatures: no-common-ligatures" class="">)
-></span> <span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">T</span><span style="font-variant-ligatures: no-common-ligatures" class="">?
{</span></div>
<div style="margin: 0px; line-height: normal;" class="">
<span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">return</span> <span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">values</span><span style="font-variant-ligatures: no-common-ligatures" class="">.</span><span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">indices</span><span style="font-variant-ligatures: no-common-ligatures" class="">.</span><span style="font-variant-ligatures: no-common-ligatures; color: #3d1d81" class="">contains</span><span style="font-variant-ligatures: no-common-ligatures" class="">(at)
?</span> <span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">values</span><span style="font-variant-ligatures: no-common-ligatures" class="">[at]</span>
<span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">as</span><span style="font-variant-ligatures: no-common-ligatures" class="">?</span>
<span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">T</span> <span style="font-variant-ligatures: no-common-ligatures" class="">:</span>
<span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">nil</span></div>
<div style="margin: 0px; line-height: normal;" class="">
<span style="font-variant-ligatures: no-common-ligatures" class="">}</span></div>
<div style="margin: 0px; line-height: normal; min-height: 13px;" class=""><br class=""></div>
<div style="margin: 0px; line-height: normal;" class="">
<span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">func</span> <span style="font-variant-ligatures: no-common-ligatures" class="">get<T>(at:</span><span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">Int</span><span style="font-variant-ligatures: no-common-ligatures" class="">, as
theType:</span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">T</span><span style="font-variant-ligatures: no-common-ligatures" class="">.Type)
-></span> <span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">T</span><span style="font-variant-ligatures: no-common-ligatures" class="">?
{</span></div>
<div style="margin: 0px; line-height: normal;" class="">
<span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">return</span> <span style="font-variant-ligatures: no-common-ligatures" class="">values.indices.contains(at) ? values[at]</span> <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">as</span><span style="font-variant-ligatures: no-common-ligatures" class="">?</span>
<span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">T</span> <span style="font-variant-ligatures: no-common-ligatures" class="">:</span>
<span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">nil</span></div>
<div style="margin: 0px; line-height: normal;" class="">
<span style="font-variant-ligatures: no-common-ligatures" class="">}</span></div>
<div style="margin: 0px; line-height: normal; min-height: 13px;" class=""><br class=""></div>
<div style="margin: 0px; line-height: normal;" class="">
<span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">mutating</span> <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">func</span> <span style="font-variant-ligatures: no-common-ligatures" class="">set<T>(at:</span><span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">Int</span><span style="font-variant-ligatures: no-common-ligatures" class="">,
to:</span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">T</span><span style="font-variant-ligatures: no-common-ligatures" class="">)
{</span></div>
<div style="margin: 0px; line-height: normal;" class="">
<span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">if</span> <span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">values</span><span style="font-variant-ligatures: no-common-ligatures" class="">.</span><span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">indices</span><span style="font-variant-ligatures: no-common-ligatures" class="">.</span><span style="font-variant-ligatures: no-common-ligatures; color: #3d1d81" class="">contains</span><span style="font-variant-ligatures: no-common-ligatures" class="">(at)
{</span> <span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">values</span><span style="font-variant-ligatures: no-common-ligatures" class="">[at] = to
}</span></div>
<div style="margin: 0px; line-height: normal;" class="">
<span style="font-variant-ligatures: no-common-ligatures" class="">}</span></div>
<div style="margin: 0px; line-height: normal;" class="">
<span style="font-variant-ligatures: no-common-ligatures" class="">}</span></div>
<div style="margin: 0px; line-height: normal; min-height: 13px;" class=""><br class=""></div>
<div style="margin: 0px; line-height: normal;" class="">
<span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">let</span> <span style="font-variant-ligatures: no-common-ligatures" class="">foo =</span>
<span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">Foo</span><span style="font-variant-ligatures: no-common-ligatures" class="">(values:
[</span><span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">1.5</span><span style="font-variant-ligatures: no-common-ligatures" class="">,</span>
<span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">2.5</span><span style="font-variant-ligatures: no-common-ligatures" class="">,</span>
<span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">3.5</span><span style="font-variant-ligatures: no-common-ligatures" class="">,</span>
<span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">1</span><span style="font-variant-ligatures: no-common-ligatures" class="">,</span>
<span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">2</span><span style="font-variant-ligatures: no-common-ligatures" class="">,</span>
<span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">3</span><span style="font-variant-ligatures: no-common-ligatures" class="">])</span></div>
<div style="margin: 0px; line-height: normal;" class="">
<span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">let</span> <span style="font-variant-ligatures: no-common-ligatures" class="">a =
foo.get(at:</span> <span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">0</span><span style="font-variant-ligatures: no-common-ligatures" class="">, as:
Double.</span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">self</span><span style="font-variant-ligatures: no-common-ligatures" class="">)</span></div>
<div style="margin: 0px; line-height: normal;" class="">
<span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">let</span> <span style="font-variant-ligatures: no-common-ligatures" class="">b:</span><span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">Double</span> <span style="font-variant-ligatures: no-common-ligatures" class="">=</span>
<span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">foo</span><span style="font-variant-ligatures: no-common-ligatures" class="">.</span><span style="font-variant-ligatures: no-common-ligatures; color: #31595d" class="">get</span><span style="font-variant-ligatures: no-common-ligatures" class="">(at:</span>
<span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">1</span><span style="font-variant-ligatures: no-common-ligatures" class="">)!</span></div>
<div style="margin: 0px; line-height: normal;" class="">
<span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">let</span> <span style="font-variant-ligatures: no-common-ligatures" class="">c:</span><span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">Int</span><span style="font-variant-ligatures: no-common-ligatures" class="">? =</span>
<span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">foo</span><span style="font-variant-ligatures: no-common-ligatures" class="">.</span><span style="font-variant-ligatures: no-common-ligatures; color: #31595d" class="">get</span><span style="font-variant-ligatures: no-common-ligatures" class="">(at:</span>
<span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">2</span><span style="font-variant-ligatures: no-common-ligatures" class="">)</span></div>
<div style="margin: 0px; line-height: normal;" class="">
<span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">let</span> <span style="font-variant-ligatures: no-common-ligatures" class="">d =
foo.get(at:</span> <span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">3</span><span style="font-variant-ligatures: no-common-ligatures" class="">, as:
Double.</span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">self</span><span style="font-variant-ligatures: no-common-ligatures" class="">)</span></div>
<div style="margin: 0px; line-height: normal;" class="">
<span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">let</span> <span style="font-variant-ligatures: no-common-ligatures" class="">e:</span><span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">Int</span> <span style="font-variant-ligatures: no-common-ligatures" class="">=</span>
<span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">foo</span><span style="font-variant-ligatures: no-common-ligatures" class="">.</span><span style="font-variant-ligatures: no-common-ligatures; color: #31595d" class="">get</span><span style="font-variant-ligatures: no-common-ligatures" class="">(at:</span>
<span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">4</span><span style="font-variant-ligatures: no-common-ligatures" class="">)!</span></div>
<div style="margin: 0px; line-height: normal;" class="">
<span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">let</span> <span style="font-variant-ligatures: no-common-ligatures" class="">f =
foo.get(at:</span> <span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">5</span><span style="font-variant-ligatures: no-common-ligatures" class="">, as:
Int.</span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">self</span><span style="font-variant-ligatures: no-common-ligatures" class="">)</span></div>
</div>
</div>
</blockquote>
<div class="">
<div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; min-height: 13px;" class=""></div>
i.e- the type is inferred from the call-site either with an
explicit variable type, or by passing in the expected type as the
second argument, which I think is a pretty neat way to do it.</div>
<div class=""><br class=""></div>
<div class="">If we could do the same with subscripts we could do
something like:</div>
<div class=""><br class=""></div>
<blockquote style="margin: 0 0 0 40px; border: none; padding: 0px;" class="">
<div class="">
<div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">struct</span> <span style="font-variant-ligatures: no-common-ligatures" class="">Foo
{</span></div>
</div>
<div class="">
<div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">var</span> <span style="font-variant-ligatures: no-common-ligatures" class="">values:[</span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">Any</span><span style="font-variant-ligatures: no-common-ligatures" class="">] =
[]</span></div>
</div>
<div class="">
<div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; min-height: 13px;" class=""><br class=""></div>
</div>
<div class="">
<div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">subscript</span><span style="font-variant-ligatures: no-common-ligatures" class=""><T>(</span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">_</span> <span style="font-variant-ligatures: no-common-ligatures" class="">at:Int)
-> T? {</span></div>
</div>
<div class="">
<div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">get {</span> <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">return</span> <span style="font-variant-ligatures: no-common-ligatures" class="">values.indices.contains(at) ? values[at]</span> <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">as</span><span style="font-variant-ligatures: no-common-ligatures" class="">? T :</span>
<span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">nil</span> <span style="font-variant-ligatures: no-common-ligatures" class="">}</span></div>
</div>
<div class="">
<div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">set {</span> <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">if</span> <span style="font-variant-ligatures: no-common-ligatures" class="">values.indices.contains(at) { values[at] = newValue }
}</span></div>
</div>
<div class="">
<div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">}</span></div>
</div>
<div class="">
<div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; min-height: 13px;" class=""><br class=""></div>
</div>
<div class="">
<div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">subscript</span><span style="font-variant-ligatures: no-common-ligatures" class=""><T>(</span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">_</span> <span style="font-variant-ligatures: no-common-ligatures" class="">at:Int, as
theType:T.Type) -> T? {</span></div>
</div>
<div class="">
<div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">return</span> <span style="font-variant-ligatures: no-common-ligatures" class="">values.indices.contains(at) ? values[at]</span> <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">as</span><span style="font-variant-ligatures: no-common-ligatures" class="">? T :</span>
<span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">nil</span></div>
</div>
<div class="">
<div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">}</span></div>
</div>
<div class="">
<div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">}</span></div>
</div>
<div class="">
<div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; min-height: 13px;" class=""><br class=""></div>
</div>
<div class="">
<div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">let</span> <span style="font-variant-ligatures: no-common-ligatures" class="">foo =</span>
<span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">Foo</span><span style="font-variant-ligatures: no-common-ligatures" class="">(values:
[</span><span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">1.5</span><span style="font-variant-ligatures: no-common-ligatures" class="">,</span>
<span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">2.5</span><span style="font-variant-ligatures: no-common-ligatures" class="">,</span>
<span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">3.5</span><span style="font-variant-ligatures: no-common-ligatures" class="">,</span>
<span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">1</span><span style="font-variant-ligatures: no-common-ligatures" class="">,</span>
<span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">2</span><span style="font-variant-ligatures: no-common-ligatures" class="">,</span>
<span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">3</span><span style="font-variant-ligatures: no-common-ligatures" class="">])</span></div>
</div>
<div class="">
<div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">let</span> <span style="font-variant-ligatures: no-common-ligatures" class="">a =</span>
<span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">foo</span><span style="font-variant-ligatures: no-common-ligatures" class="">[</span><span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">0</span><span style="font-variant-ligatures: no-common-ligatures" class="">, as:</span>
<span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">Double</span><span style="font-variant-ligatures: no-common-ligatures" class=""><span style="font-variant-ligatures: no-common-ligatures;" class="">.</span><span style="font-variant-ligatures: no-common-ligatures; color: rgb(187, 44, 162);" class="">self</span>]</span></div>
</div>
<div class="">
<div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">let</span> <span style="font-variant-ligatures: no-common-ligatures" class="">b:</span><span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">Double</span> <span style="font-variant-ligatures: no-common-ligatures" class="">=</span>
<span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">foo</span><span style="font-variant-ligatures: no-common-ligatures" class="">[</span><span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">1</span><span style="font-variant-ligatures: no-common-ligatures" class="">]!</span></div>
</div>
<div class="">
<div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">let</span> <span style="font-variant-ligatures: no-common-ligatures" class="">c:</span><span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">Int</span><span style="font-variant-ligatures: no-common-ligatures" class="">? =</span>
<span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">foo</span><span style="font-variant-ligatures: no-common-ligatures" class="">[</span><span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">2</span><span style="font-variant-ligatures: no-common-ligatures" class="">]</span></div>
</div>
<div class="">
<div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">let</span> <span style="font-variant-ligatures: no-common-ligatures" class="">d =</span>
<span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">foo</span><span style="font-variant-ligatures: no-common-ligatures" class="">[</span><span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">3</span><span style="font-variant-ligatures: no-common-ligatures" class="">, as:</span>
<span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">Double</span><span style="font-variant-ligatures: no-common-ligatures" class=""><span style="font-variant-ligatures: no-common-ligatures;" class="">.</span><span style="font-variant-ligatures: no-common-ligatures; color: rgb(187, 44, 162);" class="">self</span>]</span></div>
</div>
<div class="">
<div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">let</span> <span style="font-variant-ligatures: no-common-ligatures" class="">e:</span><span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">Int</span> <span style="font-variant-ligatures: no-common-ligatures" class="">=</span>
<span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">foo</span><span style="font-variant-ligatures: no-common-ligatures" class="">[</span><span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">4</span><span style="font-variant-ligatures: no-common-ligatures" class="">]!</span></div>
</div>
<div class="">
<div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">let</span> <span style="font-variant-ligatures: no-common-ligatures" class="">f =</span>
<span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">foo</span><span style="font-variant-ligatures: no-common-ligatures" class="">[</span><span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">5</span><span style="font-variant-ligatures: no-common-ligatures" class="">, as:</span>
<span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">Int</span><span style="font-variant-ligatures: no-common-ligatures" class=""><span style="font-variant-ligatures: no-common-ligatures;" class="">.</span><span style="font-variant-ligatures: no-common-ligatures; color: rgb(187, 44, 162);" class="">self</span>]</span></div>
</div>
</blockquote>
<div class=""><br class=""></div>
<div class="">Are generic constraints on subscripts part of the
generics manifesto?</div>
<div class=""><br class=""></div>
<div class="">
<div>
<blockquote type="cite" class="">
<div class="">On 17 Nov 2016, at 20:14, Adrian Zubarev 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="bloop_markdown" style="font-family: Helvetica, Arial; font-size: 13px; 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; background-color: rgb(254, 254, 254);">
<p style="margin: 15px 0px; -webkit-margin-before: 0px;" class="">
Dear Swift community,</p>
<p style="margin: 15px 0px;" class="">while building a framework
for BSON I had the following idea.</p>
<p style="margin: 15px 0px;" class="">Here is a snippet of some
code I do have in my module:</p>
<pre style="margin: 15px 0px; font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(204, 204, 204); overflow: auto; padding: 4px 8px; word-break: normal; word-wrap: normal;" class=""><code class="swift" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 0px; margin: 0px; padding: 0px; word-break: normal; word-wrap: normal; -webkit-margin-before: 0px;">extension Array where Element == Document.Value {
public func double(at index: Int) -> Double? {
guard self.startIndex <= index && index < self.endIndex else { return nil }
if case .double(let double) = self[index] {
return double
}
return nil
}
…
}
</code></pre>
<p style="margin: 15px 0px;" class="">This function is used to
query the array and check if the element at the given index is of a
specific type. Now I would like also to implement a semi-schema
setter.</p>
<p style="margin: 15px 0px;" class="">The problem that I see, is
the ugliness of the<span class="Apple-converted-space"> </span><code style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal; -webkit-margin-before: 0px;" class="">subscript</code><span class="Apple-converted-space"> </span>I’d create.</p>
<p style="margin: 15px 0px;" class="">Currently the code would read
nicely<span class="Apple-converted-space"> </span><code style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal; -webkit-margin-before: 0px;" class="">let d = array.double(at: 42)</code>, but after change to
a<span class="Apple-converted-space"> </span><code style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;" class="">subscript</code><span class="Apple-converted-space"> </span>the API would look
odd<span class="Apple-converted-space"> </span><code style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;" class="">array[doubleAt: 42] = 5.0</code>.</p>
<p style="margin: 15px 0px;" class="">Don’t get me wrong here, I
also have methods with larger names like<span class="Apple-converted-space"> </span><code style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal; -webkit-margin-before: 0px;" class="">public func scopedJavaScript(at index: Int) ->
…</code>. You can easily imagine that such subscripts would look
ugly<span class="Apple-converted-space"> </span><code style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;" class="">array[scopedJavaScriptAt: 123] = …</code>.</p>
<p style="margin: 15px 0px;" class="">I propose to align the design
of subscript with functions where one could optionally give
subscript a name.</p>
<pre style="margin: 15px 0px; font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(204, 204, 204); overflow: auto; padding: 4px 8px; word-break: normal; word-wrap: normal;" class=""><code class="swift" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 0px; margin: 0px; padding: 0px; word-break: normal; word-wrap: normal; -webkit-margin-before: 0px;">func name(label parameter: Type) -> ReturnType
subscript optionalName(label parameter: Type) -> ReturnType
</code></pre>
<p style="margin: 15px 0px;" class="">This change would make my API
nice and clean.<span class="Apple-converted-space"> </span><code style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal; -webkit-margin-before: 0px;" class="">array.scopedJavaScript[at: 213] = …</code></p>
<p style="margin: 15px 0px;" class="">This also might be the
opportunity to rethink the labeling rule on subscripts, but this
shall not be the main focus of this pitch.</p>
<div style="margin: 15px 0px;" class=""><br class="webkit-block-placeholder"></div>
</div>
<div class="bloop_original_html" style="font-family: Helvetica, Arial; font-size: 13px; 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; background-color: rgb(254, 254, 254);">
<div id="bloop_customfont" style="font-family: Helvetica, Arial; font-size: 13px; margin: 0px;" class=""><br class=""></div>
<br class="">
<div id="bloop_sign_1479412498260118016" class="bloop_sign">
<div style="font-family: helvetica, arial; font-size: 13px;" class="">-- <br class="">
Adrian Zubarev<br class="">
Sent with Airmail</div>
</div>
</div>
<div class="bloop_markdown" style="font-family: Helvetica, Arial; font-size: 13px; 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; background-color: rgb(254, 254, 254);">
<div style="margin: 15px 0px; -webkit-margin-before: 0px;" class=""><br class="webkit-block-placeholder"></div>
</div>
<span style="font-family: Helvetica, Arial; font-size: 13px; 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; background-color: rgb(254, 254, 254); float: none; display: inline !important;" class="">_______________________________________________</span><br style="font-family: Helvetica, Arial; font-size: 13px; 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; background-color: rgb(254, 254, 254);" class="">
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</blockquote>
</div>
<br class=""></div>
</div></div></span></blockquote></div><div class="bloop_markdown"><p></p></div></body></html>