CMake语法：如何否定if（<constant>）和if（<variable | string>）

Question

CMake的if命令[1]支持多个签名，

if(<constant>)
if(<variable|string>)
if(NOT <expression>)

如何否定前两个？

如果CMake文档是正确的（根据我的经验还不确定），那么我的问题可以归结为：

如何将常量，变量或字符串X转换为表达式，并附加要求将X评估为布尔值？

[1] https://cmake.org/cmake/help/latest/command/if.html

Answer 1

实际上，<div id="print_result" style="display:none"> <div class="row"> <!-- Start of Symptoms Card/Table/Section --> <div class="col-md-6"> <div class="card"> <div class="card-header"> <div class="text-center"><span class="section-heading-text">SYMPTOMS</span></div> </div> <?php if($quizDataArray['symptoms']): ?> {% for key, symptom in quizDataArray['symptoms'] %} <div class="col-md-12 card-box"> <div class="card-body"> <h5 class="card-title">{{ symptom['title'] }}</h5> <?php if (isset($symptom['results'])): ?> <h6 class="card-subtitle mb-2 text-muted"> {% for key, result in symptom['results'] %} <?php $causeId = key($result); ?> {{ resultKeyArray[key] }} <?php if($causeId) { ?> {{ result[causeId] }} <?php } ?> {% endfor %} </h6> <?php endif;?> </div> </div> {% endfor %} <?php endif; ?> <div class="text-center"><span class="section-heading-text">DR. RECOMMENDED PRODUCTS</span></div> <?php if($thingsToTry): ?> <?php foreach ($thingsToTry as $remedy): ?> <div class="col-md-12 card-box"> <div class="card-body"> <!-- Todo: To print image here --> <div class="col-md-8"> <div class="info-box"> <h5><?php echo $remedy['title'] ?></h5> <p> <?php echo $remedy['description'] ?> </p> </div> </div> </div> <div class="clear"></div> </div> <?php endforeach; ?> <?php endif; ?> <div class="text-center"><span class="section-heading-text">Health Food Store Recommendations</span></div> <?php if($thingsToTry): ?> {% for key, remedy in thingsToTry %} <div class="remedy-box"> <h5><strong>*{{ remedy['title'] }}</strong></h5> </div> {% endfor %} <?php endif; ?> </div> </div><!-- End of Symptoms Card/Table/Section --> </div> 只是任何参数的占位符，可以将其传递给<expression>。甚至可能的if构造的列表的标题都为“可能的表达式为”。

if