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📁 这是一本关于verilog编程语言的教程,对学习verilog语言有帮助
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4.14.1 队列操作符</div>
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队列可以与非压缩数组执行相同的操作，除下述的操作符和操作规则外，它们使用相同的操作符和操作规则。 </p><div class="Element170">
<a href="#" onclick="CopyElementToClipboard('code00165');">Copy Code</a></div>
<div class="Element13"><div class="Element12" id="code00165"><pre class="Element12"><span style="color: #0000FF">int</span> q<span style="color: #800080">[</span><span style="color: #FF0000">$</span><span style="color: #800080">]</span> <span style="color: #800080">= {</span><span style="color: #FF0000">2</span><span style="color: #800080">,</span> <span style="color: #FF0000">4</span><span style="color: #800080">,</span> <span style="color: #FF0000">8</span><span style="color: #800080">};</span>
<span style="color: #0000FF">int</span> p<span style="color: #800080">[</span><span style="color: #FF0000">$</span><span style="color: #800080">];</span>
<span style="color: #0000FF">int</span> e<span style="color: #800080">,</span> pos<span style="color: #800080">;</span>
e <span style="color: #800080">=</span> q<span style="color: #800080">[</span><span style="color: #FF0000">0</span><span style="color: #800080">];</span>     <span style="color: #008000">// 读取第一个（最左边）条目。</span>
e <span style="color: #800080">=</span> q<span style="color: #800080">[</span><span style="color: #FF0000">$</span><span style="color: #800080">];</span>     <span style="color: #008000">// 读取最后一个（最右边）条目。</span>
q<span style="color: #800080">[</span><span style="color: #FF0000">0</span><span style="color: #800080">]</span> <span style="color: #800080">=</span> e<span style="color: #800080">;</span>     <span style="color: #008000">// 写第一个元素</span>
p <span style="color: #800080">=</span> q<span style="color: #800080">;</span>        <span style="color: #008000">// 读和写整个队列（拷贝）</span>
q <span style="color: #800080">=</span> <span style="color: #800080">{</span>q<span style="color: #800080">,</span> <span style="color: #FF0000">6</span>}<span style="color: #800080">;</span>   <span style="color: #008000">// 在队列的尾部插入'6'</span>
q <span style="color: #800080">=</span> <span style="color: #800080">{</span>e<span style="color: #800080">,</span> q<span style="color: #800080">};</span>   <span style="color: #008000">// 在队列的头部插入'e'</span>
q <span style="color: #800080">=</span> q<span style="color: #800080">[</span><span style="color: #FF0000">1</span><span style="color: #800080">:</span><span style="color: #FF0000">$</span><span style="color: #800080">];</span>   <span style="color: #008000">// 删除第一个（最左边）元素</span>
q <span style="color: #800080">=</span> q<span style="color: #800080">[</span><span style="color: #FF0000">0</span><span style="color: #800080">:</span><span style="color: #FF0000">$</span><span style="color: #800080">-</span><span style="color: #FF0000">1</span><span style="color: #800080">];</span> <span style="color: #008000">// 删除最后一个（最右边）元素</span>
q <span style="color: #800080">=</span> q<span style="color: #800080">[</span><span style="color: #FF0000">1</span><span style="color: #800080">:</span><span style="color: #FF0000">$</span><span style="color: #800080">-</span><span style="color: #FF0000">1</span><span style="color: #800080">];</span> <span style="color: #008000">// 删除第一个和最后一个元素</span>
q <span style="color: #800080">=</span> <span style="color: #800080">{};</span>       <span style="color: #008000">// 清除队列（删除所有的元素）</span>
q <span style="color: #800080">=</span> <span style="color: #800080">{</span>q<span style="color: #800080">[</span><span style="color: #FF0000">0</span><span style="color: #800080">:</span>pos-1<span style="color: #800080">],</span> e<span style="color: #800080">,</span> q<span style="color: #800080">[</span>pos<span style="color: #800080">:</span><span style="color: #FF0000">$</span><span style="color: #800080">]};</span> <span style="color: #008000">// 在位置'pos'处插入'e'</span>
q <span style="color: #800080">=</span> <span style="color: #800080">{</span>q<span style="color: #800080">[</span><span style="color: #FF0000">0</span><span style="color: #800080">:</span>pos<span style="color: #800080">],</span> e<span style="color: #800080">,</span> q<span style="color: #800080">[</span>pos<span style="color: #800080">+</span>1<span style="color: #800080">:</span><span style="color: #FF0000">$</span><span style="color: #800080">]};</span> <span style="color: #008000">// 在位置'pos'之后插入'e'</span></pre></div></div>
<p class="Element10">
与数组不同，空队列，<span style="color: #800080">{}</span>，是一个有效的队列，并且可以作为某些队列操作的结果。下列规则适用于队列操作符：</p>
<ul class="Element630">
<li class="Element600"><i>Q[a:b]</i> 产生具有<i>b-a+1</i>个元素的队列。</li>
<li class="Element600">如果<i>a&gt;b</i>，那么<i>Q[a:b]</i>产生一个空队列<span style="color: #800080">{}</span>。</li>
<li class="Element600"><i>Q[n:n]</i>产生具有一个元素的队列，这个元素位于位置<i>n</i>。因此，<i>Q[n:n]==={Q[n]}</i>。</li>
<li class="Element600">如果 <i>n</i>位于<i>Q(n &lt; 0 或 n &gt; $)</i>的范围之外，那么<i>Q[n:n]</i>产生一个空队列<span style="color: #800080">{}</span>。</li>
<li class="Element600">无论是a还是b是一个包含<span style="color: #FF0000">X</span>或<span style="color: #FF0000">Z</span>的四态表达式，都产生一个空队列<span style="color: #800080">{}</span>。</li>
<li class="Element600"><i>Q[a:b]</i>中如果<i>a &lt; 0</i>，那么它与<i>Q[0:b]</i>相同。</li>
<li class="Element600"><i>Q[a:b]</i>中如果<i>b &gt; $</i>，那么它与<i>Q[a:$]</i>相同。</li>
<li class="Element600">使用无效索引值（例如包含<span style="color: #FF0000">X</span>或<span style="color: #FF0000">Z</span>的四态表示式，或者位于0...$之外的值）的读操作返回对列元素类型的初始值（如<a href="00538.html" target="topic">表4-1</a>所述）。</li>
<li class="Element600">使用无效索引值（例如包含<span style="color: #FF0000">X</span>或<span style="color: #FF0000">Z</span>的四态表示式，或者位于0...$之外的值）的写操作会被忽略，并在运行时发布警告信息。注意：向Q[$+1]写入是合法的。</li>
<li class="Element600">使用[$:N]声明右边界的队列应被限制为从0到N索引（队列的最大尺寸为N+1）。位于这个限制之外的索引是无效的，因此，在队列尾部之外的写操作会被忽略，并发布一个警告信息。这些警告信息或者在编译时发布，或者在运行时发布，只要一发现索引位于队列尺寸限制之外就发布。</li>
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注意：队列和动态数组具有相同的赋值和自变量传递语义。</p></div>
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