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<a href="#" onmousedown="showPopup(this, 'popup00042');"><img src="seealsolink.png" border="0" alt="" title=""></a> SystemVerilog 3.1a语言参考手册</div>
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3.10.4 数值表达式中的枚举类型</div>
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枚举变量的元素可以使用在数值表达式中。表达式中使用的值是与枚举值相关的数值。例如： </p><div class="Element170">
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<div class="Element13"><div class="Element12" id="code00064"><pre class="Element12"><span style="color: #0000FF">typedef enum</span> <span style="color: #800080">{</span>red<span style="color: #800080">,</span> green<span style="color: #800080">,</span> blue<span style="color: #800080">,</span> yellow<span style="color: #800080">,</span> white<span style="color: #800080">,</span> black<span style="color: #800080">}</span> Colors<span style="color: #800080">;</span>
Colors col<span style="color: #800080">;</span>
<span style="color: #0000FF">integer</span> a<span style="color: #800080">,</span> b<span style="color: #800080">;</span>
a <span style="color: #800080">=</span> blue <span style="color: #800080">*</span> <span style="color: #FF0000">3</span><span style="color: #800080">;</span>
col <span style="color: #800080">=</span> yellow<span style="color: #800080">;</span>
b <span style="color: #800080">=</span> col <span style="color: #800080">+</span> green<span style="color: #800080">;</span></pre></div></div>
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在前面的声明中，<i>blue</i>的值为<span style="color: #FF0000">2</span>。上面的例子将<i>a</i>赋值为<span style="color: #FF0000">6</span>（2*3），将<i>b</i>赋值为<span style="color: #FF0000">4</span>（3+1）。 </p>
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在表达式中使用的枚举变量或标识符自动地转换成枚举声明的基类型（或者显式地，或者使用<span style="color: #0000FF">int</span>作为缺省类型）。从一个表达式而不是相同的枚举类型对枚举变量赋值要求强制的类型转换。当强制转换到枚举类型的时候，表达式会转换到它的基本类型而不会检查值的有效性（除非使用动态强制类型转换，见<a href="00386.html" target="topic">3.15节</a>的描述）。 </p><div class="Element170">
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<div class="Element13"><div class="Element12" id="code00065"><pre class="Element12"><span style="color: #0000FF">typedef enum</span> <span style="color: #800080">{</span>Red<span style="color: #800080">,</span> Green<span style="color: #800080">,</span> Blue<span style="color: #800080">}</span> Colors<span style="color: #800080">;</span>
<span style="color: #0000FF">typedef enum</span> <span style="color: #800080">{</span>Mo<span style="color: #800080">,</span> Tu<span style="color: #800080">,</span> We<span style="color: #800080">,</span> Th<span style="color: #800080">,</span> Fr<span style="color: #800080">,</span> Sa<span style="color: #800080">,</span> Su<span style="color: #800080">}</span> Week<span style="color: #800080">;</span>
Colors C<span style="color: #800080">;</span>
Week W<span style="color: #800080">;</span>
<span style="color: #0000FF">int</span> I<span style="color: #800080">;</span>
C <span style="color: #800080">=</span> Colors<span style="color: #800080">'(</span>C<span style="color: #800080">+</span><span style="color: #FF0000">1</span><span style="color: #800080">);</span> <span style="color: #008000">// C被强制转换成一个整数，然后加1，接着转换回Colors类型</span>
C <span style="color: #800080">=</span> C <span style="color: #800080">+</span> 1<span style="color: #800080">;</span> C<span style="color: #800080">++;</span> C<span style="color: #800080">+=</span><span style="color: #FF0000">2</span><span style="color: #800080">;</span> C<span style="color: #800080">=</span>I<span style="color: #800080">;</span> <span style="color: #008000">// 非法。因为它们都是没有强制类型转换的表达式复制。</span>
I <span style="color: #800080">=</span> C <span style="color: #800080">+</span> W<span style="color: #800080">;</span> <span style="color: #008000">// 有效。C和W被自动地强制转换成int类型。</span></pre></div></div>
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SystemVerilog包含了一组特定的方法对枚举类型的值进行操作。</p></div>
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<a href="00370.html" target="topic">3.10 枚举</a></p></div>
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描述 </div></td></tr><tr>
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<a href="00375.html" target="topic">3.10.4.1 first()</a> </div></td><td class="Element206" valign="top" width="50%">
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<span style="color: #0000FF">first</span><span style="color: #800080">()</span>方法的原型为： </div></td></tr><tr>
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<a href="00376.html" target="topic">3.10.4.2 last()</a> </div></td><td class="Element206" valign="top" width="50%">
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<span style="color: #0000FF">last</span><span style="color: #800080">()</span>方法的原型为： </div></td></tr><tr>
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<a href="00377.html" target="topic">3.10.4.3 next()</a> </div></td><td class="Element206" valign="top" width="50%">
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<span style="color: #0000FF">next</span><span style="color: #800080">()</span>方法的原型为： </div></td></tr><tr>
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<a href="00378.html" target="topic">3.10.4.4 prev()</a> </div></td><td class="Element206" valign="top" width="50%">
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<span style="color: #0000FF">prev</span><span style="color: #800080">()</span>方法的原型为： </div></td></tr><tr>
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<a href="00379.html" target="topic">3.10.4.5 num()</a> </div></td><td class="Element206" valign="top" width="50%">
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<span style="color: #0000FF">num</span><span style="color: #800080">()</span>方法的原型为： </div></td></tr><tr>
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<a href="00380.html" target="topic">3.10.4.6 name()</a> </div></td><td class="Element206" valign="top" width="50%">
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<span style="color: #0000FF">name</span><span style="color: #800080">()</span>方法的原型为： </div></td></tr><tr>
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<a href="00381.html" target="topic">3.10.4.7 使用枚举类型的方法</a> </div></td><td class="Element206" valign="top" width="50%">
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下面的代码片断展示了如何显示一个枚举变量所有成员的名字和值。 </div></td></tr></table></div></div>
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