calculation taking a context and returning a value.</dd>
</dl>
</li>
</ul>
<a name="reducer-java.lang.Object-clojure.lang.IFn-">
<!--   -->
</a>
<ul class="blockList">
<li class="blockList">
<h4>reducer</h4>
<pre>public static&nbsp;java.lang.Object&nbsp;reducer(java.lang.Object&nbsp;colname,
                                       clojure.lang.IFn&nbsp;perElemFn)</pre>
<div class="block"><p>Create a custom reducer. <code>perElemFn</code> is passed the last return value as the first argument followed by a val