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<h1 id="附录-c表达式"><a class="header" href="#附录-c表达式">附录 C表达式</a></h1>
<p><a href="https://course.rs/basic/base-type/statement-expression.html">语句与表达式</a>章节中,我们对表达式有过介绍,下面对这些常用表达式进行一一说明。</p>
<h3 id="基本表达式"><a class="header" href="#基本表达式">基本表达式</a></h3>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>let n = 3;
let s = "test";
<span class="boring">}</span></code></pre></pre>
<h3 id="if-表达式"><a class="header" href="#if-表达式">if 表达式</a></h3>
<pre><pre class="playground"><code class="language-rust edition2021">fn main() {
let var1 = 10;
let var2 = if var1 &gt;= 10 {
var1
} else {
var1 + 10
};
println!("{}", var2);
}</code></pre></pre>
<p>通过 <code>if</code> 表达式将值赋予 <code>var2</code></p>
<p>你还可以在循环中结合 <code>continue</code><code>break</code> 来使用:</p>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>let mut v = 0;
for i in 1..10 {
v = if i == 9 {
continue
} else {
i
}
}
println!("{}", v);
<span class="boring">}</span></code></pre></pre>
<h3 id="if-let-表达式"><a class="header" href="#if-let-表达式">if let 表达式</a></h3>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>let o = Some(3);
let v = if let Some(x) = o {
x
} else {
0
};
<span class="boring">}</span></code></pre></pre>
<h3 id="match-表达式"><a class="header" href="#match-表达式">match 表达式</a></h3>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>let o = Some(3);
let v = match o {
Some(x) =&gt; x,
_ =&gt; 0
};
<span class="boring">}</span></code></pre></pre>
<h3 id="loop-表达式"><a class="header" href="#loop-表达式">loop 表达式</a></h3>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>let mut n = 0;
let v = loop {
if n == 10 {
break n
}
n += 1;
};
<span class="boring">}</span></code></pre></pre>
<h3 id="语句块"><a class="header" href="#语句块">语句块</a></h3>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>let mut n = 0;
let v = {
println!("before: {}", n);
n += 1;
println!("after: {}", n);
n
};
println!("{}", v);
<span class="boring">}</span></code></pre></pre>
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