https://community.appian.com/support/w/kb/399/kb-1182-expression-evaluation-error-at-function-reduce-line-error-thrown-when-using-reduce-function-with-nested-listsen-USTelligent Community 12https://community.appian.com/support/w/kb/399/kb-1182-expression-evaluation-error-at-function-reduce-line-error-thrown-when-using-reduce-function-with-nested-listsMon, 06 Mar 2017 19:19:16 GMTd3a83456-d57b-489c-a84c-4e8267bb592a:a8b4b20b-d415-4e4d-b397-6ebac14477dfNick Vigilantehttps://community.appian.com/support/w/kb/399/kb-1182-expression-evaluation-error-at-function-reduce-line-error-thrown-when-using-reduce-function-with-nested-lists#commentsCurrent Revision posted to Appian Knowledge Base by Nick Vigilante on 3/6/2017 7:19:16 PM<br /> <div class="row content_container"> <h2 id="symptoms">Symptoms</h2> <p>When using the <code>reduce()</code> function and the &quot;function&quot; parameter is set to a function whose result is an array (i.e. <code>apply()</code>) the following error is observed:</p> <p><a href="/cfs-file/__key/communityserver-wikis-components-files/00-00-00-00-11/pastedimage1488827889006v1.png"><img src="/resized-image/__size/1200x55555/__key/communityserver-wikis-components-files/00-00-00-00-11/pastedimage1488827889006v1.png" alt=" " /></a></p> <pre><code>Expression evaluation error at function &lsquo;reduce&rsquo; [line #]: </code></pre> <h2 id="cause">Cause</h2> <p>This issue has been reported to the Appian product team. The reference number for this issue is <strong>AN-70271</strong>.</p> <h2 id="action">Action</h2> <p>Do not use looping functions within a <code>reduce()</code> function.</p> <h2 id="affected-versions">Affected Versions</h2> <p>This article applies to all versions of Appian.</p> </div> <p>Last Reviewed: March 2017</p><div style="clear:both;"></div> <div style="font-size: 90%;">Tags: known issues, expression rules, application design, open issues</div>