title: What does the question mark at the end of a method name mean in Ruby?
body: <p>What is the purpose of the question mark operator in Ruby?</p>
  
  <p>Sometimes it appears like this:</p>
  
  <pre><code>assert !product.valid?
  </code></pre>
  
  <p>sometimes it's in an <code>if</code> construct.</p>