title: Use of special characters in function names
body: <p>In Ruby, a standard convention is to use a question mark at the end of a method name to indicate the method returns a boolean result:</p>
  
  <pre><code>[].empty?   #=&gt; true 
  </code></pre>
  
  <p>Another standard convention is to end a method name with an exclamation point if the method is destructive (that is, it modifies the original data):</p>
  
  <pre><code>mylist.sort! # sort mylist in-place
  </code></pre>
  
  <p>Recently I have seen these same conventions used in Scheme. Which makes me wonder, what other languages use/support this convention? Are there any other special characters that are commonly used for naming by these or other languages?</p>