title: Function of '+' in #if defined?
body: <pre><code>#include &lt;stdio.h&gt;
  
  #define MIN 0
  
  #if defined(MIN) + defined(MAX)
  
  #define MAX 10
  
  #endif
  
  int main()
  
  {
  
      printf("%d %d\n", MAX, MIN);
  
      return 0;
  
  }  
  </code></pre>
  
  <p><strong>Output</strong><br>
  <code>10 0</code><br>
  What is the meaning of <code>#if defined(MIN) + defined(MAX)</code>?<br>
  Why it is working when <code>#define MAX 10</code> is defined later?</p>