title: $idx and $len in a dust.js conditional statement
body: <p>The documentation on dust is just <em>awful</em>, I've already perused everything I can possibly find and cannot figure out how this is supposed to work.</p>
  
  <p>I'm having this problem with the supposed special values $idx and $len, which, if I have guessed correctly, return the current index while iterating over an array-like section and the length of said array-like section. I have an @if condition (multiple actually) that I'm trying to workout to format a template, and the values are just not working as near as I can tell, which brings me to the following questions:</p>
  
  <ol>
  <li>Are $idx and $len actual specials in dust.js?</li>
  <li>Can you use them in an @if, and if so, how?</li>
  <li>Assuming 1=true, is $idx zero-based?</li>
  </ol>
  
  <p>Here is my template:</p>
  
  <pre><code>{#myArray}
    {name}{@sep}, {/sep}{@if cond="('{$idx}' == '{$len} - 2')"}and {/if}{@if cond="('{$idx}' == '{$len} - 1')"}{@if cond="('{$len}' == '1')"} is {:else} are {/if}here.{/if}
  {/myArray}
  </code></pre>
  
  <p>What it's supposed to do:</p>
  
  <ul>
  <li>If there is one person, render the string "Jake is here."</li>
  <li>If there are two people, render the string "Jake and John are here."</li>
  <li>If there are three or more people, render the string "Jake, John, and Bill are here." (obviously, adding the comma-separated names as necessary)</li>
  </ul>
  
  <p>If the $idx and $len specials work the way one would think they work, this template would do what I want it to, as near as I can tell, however, I don't think either of $idx or $len (or both) are implemented. If they are not, how do I create a template that does what I want?</p>