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<li><em>KusonStack一站式可编程配置技术栈: <a href="https://github.com/KusionStack/kusion">https://github.com/KusionStack/kusion</a></em></li>
<li><em>凹语言™: <a href="https://github.com/wa-lang/wa">https://github.com/wa-lang/wa</a></em></li>
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<h2 id="34-布尔型"><a class="header" href="#34-布尔型">3.4. 布尔型</a></h2>
<p>一个布尔类型的值只有两种true和false。if和for语句的条件部分都是布尔类型的值并且==和&lt;等比较操作也会产生布尔型的值。一元操作符<code>!</code>对应逻辑非操作,因此<code>!true</code>的值为<code>false</code>,更罗嗦的说法是<code>(!true==false)==true</code>虽然表达方式不一样不过我们一般会采用简洁的布尔表达式就像用x来表示<code>x==true</code></p>
<p>布尔值可以和&amp;&amp;AND和||OR操作符结合并且有短路行为如果运算符左边值已经可以确定整个布尔表达式的值那么运算符右边的值将不再被求值因此下面的表达式总是安全的</p>
<pre><code class="language-Go">s != &quot;&quot; &amp;&amp; s[0] == 'x'
</code></pre>
<p>其中s[0]操作如果应用于空字符串将会导致panic异常。</p>
<p>因为<code>&amp;&amp;</code>的优先级比<code>||</code>高(助记:<code>&amp;&amp;</code>对应逻辑乘法,<code>||</code>对应逻辑加法,乘法比加法优先级要高),下面形式的布尔表达式是不需要加小括弧的:</p>
<pre><code class="language-Go">if 'a' &lt;= c &amp;&amp; c &lt;= 'z' ||
'A' &lt;= c &amp;&amp; c &lt;= 'Z' ||
'0' &lt;= c &amp;&amp; c &lt;= '9' {
// ...ASCII letter or digit...
}
</code></pre>
<p>布尔值并不会隐式转换为数字值0或1反之亦然。必须使用一个显式的if语句辅助转换</p>
<pre><code class="language-Go">i := 0
if b {
i = 1
}
</code></pre>
<p>如果需要经常做类似的转换,包装成一个函数会更方便:</p>
<pre><code class="language-Go">// btoi returns 1 if b is true and 0 if false.
func btoi(b bool) int {
if b {
return 1
}
return 0
}
</code></pre>
<p>数字到布尔型的逆转换则非常简单,不过为了保持对称,我们也可以包装一个函数:</p>
<pre><code class="language-Go">// itob reports whether i is non-zero.
func itob(i int) bool { return i != 0 }
</code></pre>
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