title: Quote a C++ MACRO parameter
body: <p>I have the following <em>template</em>:</p>
  
  <pre><code>variable = config["variable"] ? config["variable"].as&lt;type&gt;() : default;
  </code></pre>
  
  <p>I want to create a macro to have this done for me faster, since writing this many times becomes boring. I would try something like:</p>
  
  <pre><code>#define CONFIG_PARAM(config, key, type, alt) config["key"] ? config["key"].as&lt;type&gt; : alt;
  
  title = CONFIG_PARAM(root, "title", std::string, "")
  </code></pre>
  
  <p>It's obvious that that wouldn't work. How can I get this done?</p>