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<a href="00865.html" target="topic">第十二章 随机约束</a></div>
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12.6 内联约束 — randomize() with</div>
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通过使用<span style="color: #0000FF">randomize</span><span style="color: #800080">()</span>...<span style="color: #0000FF">with</span>结构，用户可以在<span style="color: #0000FF">randomize</span><span style="color: #800080">()</span>方法的调用点上声明内联约束。这些额外的约束与对象约束一起应用。 </p>
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<span style="color: #0000FF">randomize</span><span style="color: #800080">()</span>...<span style="color: #0000FF">with</span>的语法如下： </p><div class="Element170">
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<div class="Element13"><div class="Element12" id="code00442"><pre class="Element12">inline_constraint _declaration ::= <span style="color: #008000">// 没有包含在附录A中</span>
class_variable_identifier<strong><span style="color: #FF0000">.randomize</span></strong>[<strong><span style="color: #FF0000">(</span></strong>[variable_identifier_list | <strong><span style="color: #FF0000">null</span></strong>]<strong><span style="color: #FF0000">)</span></strong>]
<strong><span style="color: #FF0000">with</span></strong> constraint_block</pre></div></div>
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<strong>语法12-9 — 内联约束语法（没有包含在附录A中）</strong></p><p class="Element10">
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<i>class_variable_identifier</i>是一个被实例的对象的名字。 </p>
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未命名的<i>constraint_block</i>包含了额外的内联约束，这些内联约束与在类内声明的对象约束一起应用。 </p>
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例如： </p><div class="Element170">
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<div class="Element13"><div class="Element12" id="code00443"><pre class="Element12"><span style="color: #0000FF">class</span> SimpleSum
<span style="color: #0000FF">rand bit</span> <span style="color: #800080">[</span><span style="color: #FF0000">7</span><span style="color: #800080">:</span><span style="color: #FF0000">0</span><span style="color: #800080">]</span> x<span style="color: #800080">,</span> y<span style="color: #800080">,</span> z<span style="color: #800080">;</span>
<span style="color: #0000FF">constraint</span> c <span style="color: #800080">{</span>z <span style="color: #800080">==</span> x <span style="color: #800080">+</span> y<span style="color: #800080">;}</span>
<span style="color: #0000FF">endclass</span>
<span style="color: #0000FF">task</span> InlineConstraintDemo<span style="color: #800080">(</span>SimpleSum p<span style="color: #800080">);</span>
<span style="color: #0000FF">int</span> success<span style="color: #800080">;</span>
success <span style="color: #800080">=</span> p<span style="color: #800080">.</span><span style="color: #0000FF">randomize</span><span style="color: #800080">()</span> <span style="color: #0000FF">with</span> <span style="color: #800080">{</span>x <span style="color: #800080"><</span> y<span style="color: #800080">;};</span>
<span style="color: #0000FF">endtask</span></pre></div></div>
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这个简单的例子在前面章节已经使用过，然而在这里我们使用<span style="color: #0000FF">randomize</span><span style="color: #800080">()</span>...<span style="color: #0000FF">with</span>来引入一个额外的x <span style="color: #800080"><</span> y的约束。 </p>
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<span style="color: #0000FF">randomize</span><span style="color: #800080">()</span>...<span style="color: #0000FF">with</span>结构可以出现在表达式可以出现的任何地方。紧跟在with之后的约束块可以包含在类中声明的所有相同的约束类型和格式。<span style="color: #0000FF">randomize</span><span style="color: #800080">()</span>...<span style="color: #0000FF">with</span>约束块还可以引用本地变量以及任务和函数的参数，因此我们不需要将一个本地状态映射成对象类中的成员变量。一个约束块中变量名的作用范围由内而外为：<span style="color: #0000FF">randomize</span><span style="color: #800080">()</span>...<span style="color: #0000FF">with</span>对象类、自动和本地变量、任务和函数参数、类变量、包围范围内的变量。<span style="color: #0000FF">randomize</span><span style="color: #800080">()</span>...<span style="color: #0000FF">with</span>类在最内层的嵌套中被引入到作用范围。 </p>
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在下面的例子中，<span style="color: #0000FF">randomize</span><span style="color: #800080">()</span>...<span style="color: #0000FF">with</span>类是foo。 </p><div class="Element170">
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<div class="Element13"><div class="Element12" id="code00444"><pre class="Element12"><span style="color: #0000FF">class</span> Foo<span style="color: #800080">;</span>
<span style="color: #0000FF">rand integer</span> x<span style="color: #800080">;</span>
<span style="color: #0000FF">endclass</span>
<span style="color: #0000FF">class</span> Bar<span style="color: #800080">;</span>
<span style="color: #0000FF">integer</span> x<span style="color: #800080">;</span>
<span style="color: #0000FF">integer</span> y<span style="color: #800080">;</span>
<span style="color: #0000FF">task</span> doit<span style="color: #800080">(</span>Foo f<span style="color: #800080">,</span> <span style="color: #0000FF">integer</span> x<span style="color: #800080">,</span> <span style="color: #0000FF">integer</span> z<span style="color: #800080">);</span>
<span style="color: #0000FF">int</span> result<span style="color: #800080">;</span>
result <span style="color: #800080">=</span> f<span style="color: #800080">.</span><span style="color: #0000FF">randomize</span><span style="color: #800080">()</span> <span style="color: #0000FF">with</span> <span style="color: #800080">{</span>x <span style="color: #800080"><</span> y <span style="color: #800080">+</span> z<span style="color: #800080">;};</span>
<span style="color: #0000FF">endtask</span>
<span style="color: #0000FF">endclass</span></pre></div></div>
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在<i>f<span style="color: #800080"></i>.</span><span style="color: #0000FF">randomize</span><span style="color: #800080">()</span> <span style="color: #0000FF">with</span>约束块中，<i>x</i>是<i>foo</i>类的一个成员，并将<i>x</i>隐藏在<i>Bar</i>类中。它还将<i>x</i>参数隐藏在<i>doit<span style="color: #800080"></i>()</span>任务中。<i>v</i>是<i>Bar</i>的一个成员。<i>z</i>是一个本地参数。</p></div>
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<a href="00865.html" target="topic">第十二章 随机约束</a></p></div>
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