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<h1 class="title">References and Borrowing</h1>
<p><small>There is a new edition of the book and this is an old link.</small></p>
<blockquote>
<p>A reference <em>refers</em> to a value but does not own it.
Because it does not own it, the value it points to will not be dropped when the reference goes out of scope.</p>
</blockquote>
<pre class="rust rust-example-rendered">
<span class="kw">fn</span> <span class="ident">calculate_length</span>(<span class="ident">s</span>: <span class="kw-2">&</span><span class="ident">String</span>) <span class="op">-></span> <span class="ident">usize</span> { <span class="comment">// s is a reference to a String</span>
<span class="ident">s</span>.<span class="ident">len</span>()
} <span class="comment">// Here, s goes out of scope. But because it does not have ownership of what</span>
<span class="comment">// it refers to, nothing happens.</span><a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Afn%20calculate_length(s%3A%20%26String)%20-%3E%20usize%20%7B%20%2F%2F%20s%20is%20a%20reference%20to%20a%20String%0A%20%20%20%20s.len()%0A%7D%20%2F%2F%20Here%2C%20s%20goes%20out%20of%20scope.%20But%20because%20it%20does%20not%20have%20ownership%20of%20what%0A%20%20%2F%2F%20it%20refers%20to%2C%20nothing%20happens.%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/ch04-02-references-and-borrowing.html">In the second edition: Ch 4.02 — References and Borrowing</a></strong></li>
<li><small><a href="first-edition/references-and-borrowing.html">In the first edition: Ch 3.9 — References and Borrowing</a></small></li>
</ul>
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