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12.11.1 为范围变量添加约束 — std::randomize() with</div>
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范围随机化函数的<span style="color: #0000FF">std</span><span style="color: #800080">::</span><span style="color: #0000FF">randomize</span><span style="color: #800080">() </span><span style="color: #0000FF">with</span>形式允许用户为本地范围变量指定随机约束。当说明约束的时候，范围随机化函数的参数指定的变量变成了随机变量，所有其它变量被认为是状态变量。 </p><div class="Element170">
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<div class="Element13"><div class="Element12" id="code00456"><pre class="Element12"><span style="color: #0000FF">task</span> stimulus <span style="color: #800080">(</span>int length<span style="color: #800080">);</span>
<span style="color: #0000FF">int</span> a<span style="color: #800080">,</span> b<span style="color: #800080">,</span> c<span style="color: #800080">,</span> success<span style="color: #800080">;</span>
success <span style="color: #800080">=</span> <span style="color: #0000FF">std</span><span style="color: #800080">::</span><span style="color: #0000FF">randomize</span><span style="color: #800080">(</span>a<span style="color: #800080">,</span> b<span style="color: #800080">,</span> c<span style="color: #800080">)</span> <span style="color: #0000FF">with</span> <span style="color: #800080">{</span>a <span style="color: #800080"><</span> b<span style="color: #800080">;</span> a <span style="color: #800080">+</span> b <span style="color: #800080"><</span> length<span style="color: #800080">};</span>
...
success <span style="color: #800080">=</span> <span style="color: #0000FF">std</span><span style="color: #800080">::</span><span style="color: #0000FF">randomize</span><span style="color: #800080">(</span>a<span style="color: #800080">,</span> b<span style="color: #800080">)</span> <span style="color: #0000FF">with</span> <span style="color: #800080">{</span>b <span style="color: #800080">-</span> a <span style="color: #800080">></span> length<span style="color: #800080">};</span>
...
<span style="color: #0000FF">endtask</span></pre></div></div>
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上面例子中的任务（<span class="Element146">stimulus</span>）将<span style="color: #0000FF">std</span><span style="color: #800080">::</span><span style="color: #0000FF">randomize</span>调用了两次，从而为它的本地变量<span class="Element146">a</span>、<span class="Element146">b</span>和<span class="Element146">c</span>产生了两组随机值。在第一次调用中，<span class="Element146">a</span>和<span class="Element146">b</span>被约束成<span class="Element146">a</span>小于<span class="Element146">b</span>，并且它们的和小于任务参数<span class="Element146">length</span>（它被指定成一个状态变量）。在第二次调用中，变量<span class="Element146">a</span>和<span class="Element146">b</span>被约束成它们的差大于状态变量<span class="Element146">length</span>。</p></div>
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