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<h1 class="title">Patterns</h1>
<nav id="TOC"><ul></ul></nav><p><small>There is a new edition of the book and this is an old link.</small></p>
<blockquote>
<p>Patterns are a special syntax within Rust for matching against the structure of our types, complex or simple.
A pattern is made up of some combination of literals; destructured arrays, enums, structs, or tuples; variables, wildcards, and placeholders.
These pieces describe the “shape” of the data we’re working with.</p>
</blockquote>
<pre class="rust rust-example-rendered">
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="number">5</span>);
<span class="kw">let</span> <span class="ident">y</span> <span class="op">=</span> <span class="number">10</span>;
<span class="kw">match</span> <span class="ident">x</span> {
<span class="prelude-val">Some</span>(<span class="number">50</span>) <span class="op">=></span> <span class="macro">println</span><span class="macro">!</span>(<span class="string">"Got 50"</span>),
<span class="prelude-val">Some</span>(<span class="ident">y</span>) <span class="op">=></span> <span class="macro">println</span><span class="macro">!</span>(<span class="string">"Matched, y = {:?}"</span>, <span class="ident">y</span>),
_ <span class="op">=></span> <span class="macro">println</span><span class="macro">!</span>(<span class="string">"Default case, x = {:?}"</span>, <span class="ident">x</span>),
}<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Alet%20x%20%3D%20Some(5)%3B%0Alet%20y%20%3D%2010%3B%0A%0Amatch%20x%20%7B%0A%20%20%20%20Some(50)%20%3D%3E%20println!(%22Got%2050%22)%2C%0A%20%20%20%20Some(y)%20%3D%3E%20println!(%22Matched%2C%20y%20%3D%20%7B%3A%3F%7D%22%2C%20y)%2C%0A%20%20%20%20_%20%3D%3E%20println!(%22Default%20case%2C%20x%20%3D%20%7B%3A%3F%7D%22%2C%20x)%2C%0A%7D%0A%7D">Run</a></pre>
<hr />
<p>Here are the relevant sections in the new and old books:</p>
<ul>
<li><strong><a href="second-edition/ch18-00-patterns.html">In the second edition: Ch 18.03 — Patterns</a></strong></li>
<li><a href="second-edition/ch06-02-match.html#patterns-that-bind-to-values">In the second edition: Ch 6.02 — Match</a></li>
<li><small><a href="first-edition/patterns.html">In the first edition: Ch 3.15 — Patterns</a></small></li>
</ul>
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