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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>Actually the generics manifesto has a nice solution on how we could extend tuples in the future. Parameterized extensions + variadic generics could allow us a lot.</p>
<p>I played with a simple sketch on how it could be enhanced. Especially I personally like the ability of fixed vs. unbound parameter length.</p>
<p>Here is the sketch:</p>
<h3 id="vectors">Vectors</h3>
<ul>
<li>A <em>vector</em> contains at least one type.</li>
<li><code>vector T</code> - is a list of type <code>T</code> of an arbitrary length, such as T<sub>1</sub>, T<sub>2</sub>, …</li>
<li><code>vector(n) T</code> - is a list with the length of maximal n T’s, such as T<sub>1</sub>, T<sub>2</sub>, … , T<sub>n</sub></li>
</ul>
<pre><code class="swift">// vectorized tuple with arbitrary length (like an existetial that can accept a tuple of type `T` of any length)
var t1: (vector Int) = (1, 2)
t1 = (1, 2, 3)
t1 = (1, 2, 3, 4)
// vectorized tuple of fixed length
let t2: (vector(10) Int) = (1, 2, 3, 4, 5, 6, 7, 8, 9, 0)
// replacing the variadic syntax `T...` with vectors
func foo1(_: vector Int)
func foo2(_: (vector Int))
func foo3(_: vector (vector Int))
foo1(1, 2, 3, 4)
foo2((1, 2, 3, 4, 5))
foo3((1, 2), (1, 2, 3, 4), (1, 2, 3))
// variadic with fixed length
func foo4(_: vector(3) Int)
func foo5(_: vector(3) (vector(3) Int))
foo4(1, 2, 3)
foo5((1, 2, 3, 4), (1, 2, 3, 4), (1, 2, 3, 4), (1, 2, 3, 4))
// `foo5` would be equivalent to `func foo5(_: (Int, Int, Int), _: (Int, Int, Int), _: (Int, Int, Int))`
func foo3(_: vector (vector Int))
</code></pre>
<h3 id="variadicgenerics">Variadic generics</h3>
<ul>
<li><code>generic T</code> - a constraint applied to <code>T</code> to indicated that <code>T</code> is not fixed and can be changed iteratively.</li>
<li><code>generic</code> does not provide any information about the length of the parameter list.</li>
</ul>
<pre><code class="swift">// combined with vectors we'll get variadic generics
// the reason why we need both `vector` and `params` is to be able to tell the compiler that `T` has
// an arbitrary paramater length (vector) *and* that `T` can change iteratively (generic)
struct ZipSequence<vector generic T> : Sequence where T : Sequence { ... }
func zip<vector generic T>(_ sequences: vector T) -> ZipSequence<vector T> where T : Sequence { ... }
</code></pre>
<hr>
<p>The <code>generic</code> keyword is more like a placeholder in that sketch. </p>
<hr>
<p>Extending tuples:</p>
<pre><code class="swift">// parameterized extensions
// vectorized tuples
extension<T> (vector T) : MutableCollection { ... }
// conditional conformances
extension<vector generic T> (vector T) : Equatable where T : Equatable { ... }
</code></pre>
<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_1488458752260758784" 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 2. März 2017 um 12:24:03, Anton Zhilin (<a href="mailto:antonyzhilin@gmail.com">antonyzhilin@gmail.com</a>) schrieb:</p> <blockquote type="cite" class="clean_bq"><span><div><div></div><div>
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<p style="margin:0px 0px 1.2em!important">I think that tuples
should remain what they are now. Static-length vectors should be
types on their own and interact with tuples, with structs and with
<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">
Array<…></code> in the same way.</p>
<p style="margin:0px 0px 1.2em!important"><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">
newtype</code> should be what enables extension of tuples:</p>
<pre style="font-size:0.85em;font-family:Consolas,Inconsolata,Courier,monospace;font-size:1em;line-height:1.2em;margin:1.2em 0px"><code class="hljs language-swift" 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;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)">newtype <span class="hljs-type" style="color:rgb(68,85,136);font-weight:bold">Money</span> = (<span class="hljs-type" style="color:rgb(68,85,136);font-weight:bold">Int</span>, <span class="hljs-type" style="color:rgb(68,85,136);font-weight:bold">Int</span>)
<span class="hljs-class"><span class="hljs-keyword" style="color:rgb(51,51,51);font-weight:bold">extension</span> <span class="hljs-title" style="color:rgb(153,0,0);font-weight:bold;color:rgb(68,85,136);font-weight:bold">Money</span>: <span class="hljs-title" style="color:rgb(153,0,0);font-weight:bold;color:rgb(68,85,136);font-weight:bold">CustomStringConvertible</span> </span>{
<span class="hljs-keyword" style="color:rgb(51,51,51);font-weight:bold">var</span> description: <span class="hljs-type" style="color:rgb(68,85,136);font-weight:bold">String</span> {
<span class="hljs-keyword" style="color:rgb(51,51,51);font-weight:bold">return</span> <span class="hljs-type" style="color:rgb(68,85,136);font-weight:bold">String</span>(format: <span class="hljs-string" style="color:rgb(221,17,68)">"$%d.%02d"</span>, arguments: [getSelfFirst, getSelfSecond])
}
}
<span class="hljs-keyword" style="color:rgb(51,51,51);font-weight:bold">let</span> x = (<span class="hljs-number" style="color:rgb(0,128,128)">0</span>, <span class="hljs-number" style="color:rgb(0,128,128)">42</span>)
<span class="hljs-keyword" style="color:rgb(51,51,51);font-weight:bold">let</span> y = x <span class="hljs-keyword" style="color:rgb(51,51,51);font-weight:bold">as</span> <span class="hljs-type" style="color:rgb(68,85,136);font-weight:bold">Money</span> <span class="hljs-comment" style="color:rgb(153,153,136);font-style:italic">// error</span>
<span class="hljs-built_in" style="color:rgb(0,134,179)">print</span>(x.description) <span class="hljs-comment" style="color:rgb(153,153,136);font-style:italic">// error</span>
<span class="hljs-keyword" style="color:rgb(51,51,51);font-weight:bold">let</span> z = <span class="hljs-type" style="color:rgb(68,85,136);font-weight:bold">Money</span>(<span class="hljs-number" style="color:rgb(0,128,128)">0</span>, <span class="hljs-number" style="color:rgb(0,128,128)">42</span>)
<span class="hljs-built_in" style="color:rgb(0,134,179)">print</span>(z.description) <span class="hljs-comment" style="color:rgb(153,153,136);font-style:italic">//=> $0.42</span>
</code></pre>
<p style="margin:0px 0px 1.2em!important">Here, <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">
getSelfFirst</code> and <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">
getSelfSecond</code> are placeholders for some syntax to access the
underlying type.</p>
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