https://community.appian.com/discussions/f/rules/820/hey-all-i-m-interested-in-writing-a-simple-expression-rule-which-willHey all, I&#39;m interested in writing a simple expression rule which will take two arrays (let&#39;s say integers, for now), ri!bigArray and ri!smallArray -- and the return will be the indices (if any) of where any members of &#39;small&#39; are in &#39;big&#39;. Sort of likeen-USTelligent Community 12https://community.appian.com/thread/2770?ContentTypeID=1Fri, 07 Jun 2013 20:23:58 GMTd3a83456-d57b-489c-a84c-4e8267bb592a:feb76c28-679a-45ba-b59b-ccd110365507Owen ParrishI would discourage the use of undocumented functions.<br /><br />Instead, you could use reduce() and 2 expression rules to achieve the desired result:<br /><br />Rule 1<br />--------<br />Name: appendIndexIfContains <br />Inputs: indices (Integer, Multiple), bigArrayValue (Integer), bigArrayIndex (Integer), smallArray (Integer, Multiple)<br />Expression: =if(contains(ri!smallArray,bigArrayValue),append(ri!indices,ri!bigArrayIndex),ri!indices)<br /><br />Rule 2<br />--------<br />Name: getIndicesWhereBigContainsSmall<br />Inputs: bigArray (Integer, Multiple), smallArray (Integer, Multiple)<br />Expression: =reduce(rule!appendIndexIfContains, {},merge(ri!bigArray,enumerate(length(ri!bigArray))+1),ri!smallArray)<div style="clear:both;"></div>https://community.appian.com/thread/2769?ContentTypeID=1Fri, 07 Jun 2013 19:51:20 GMTd3a83456-d57b-489c-a84c-4e8267bb592a:ebc04b49-b8f3-4b24-8ca6-06b9ee1bfa68Mike Schmittwhere() doesn&#39;t have a way to replicate the functionality I was originally asking about, though (the ability to find the &quot;where&quot; indexes of multiple objects within an array). wherecontains() certainly does, thanks to subhankarb for mentioning that.<div style="clear:both;"></div>https://community.appian.com/thread/2768?ContentTypeID=1Fri, 07 Jun 2013 19:49:16 GMTd3a83456-d57b-489c-a84c-4e8267bb592a:e43f36aa-1404-4986-962b-b3b9da478e8bOwen ParrishIn 6.7 and greater there is a where() function: <a href="https://forum.appian.com/suite/wiki/latest/Array_Functions#where.28.29">forum.appian.com/.../Array_Functions</a><div style="clear:both;"></div>https://community.appian.com/thread/2760?ContentTypeID=1Fri, 07 Jun 2013 12:04:59 GMTd3a83456-d57b-489c-a84c-4e8267bb592a:f10843ad-d0b7-47df-9feb-80b0d5877c49moritzwThat&#39;s definetely the nicest approach. <br /><br />I guess though that it&#39;s possible that non documented functions can get deprecated in any release, right? Or are there maybe any other risks in using undocumented functions?<div style="clear:both;"></div>https://community.appian.com/thread/2759?ContentTypeID=1Fri, 07 Jun 2013 11:53:09 GMTd3a83456-d57b-489c-a84c-4e8267bb592a:bf140a3b-2a5e-4f91-ba5b-0b2d8def7bf8subhankarbCan also go for wherecontains(ri!smallArray,ri!bigArray). it is not an documented function. So you will not be able to search in appin expression editor. But using the function in exp editor will give you the desired output.<div style="clear:both;"></div>https://community.appian.com/thread/2746?ContentTypeID=1Wed, 05 Jun 2013 19:33:45 GMTd3a83456-d57b-489c-a84c-4e8267bb592a:dfba345b-f443-49e3-952c-60173f475315moritzwYep. Something like this:<br />=apply(fn!displayvalue, ri!values, ri!array, enumerate(count(ri!array))+1, &quot;no&quot;)<br />would also work. Not sure which solution is better performance wise.<div style="clear:both;"></div>https://community.appian.com/thread/2745?ContentTypeID=1Wed, 05 Jun 2013 19:13:22 GMTd3a83456-d57b-489c-a84c-4e8267bb592a:4db1e37f-9c85-4fec-859b-b6e197ba1eaeshelzleMaybe this one<br /><br />=apply(fn!displayvalue, {1, 5, 12}, {1,3,5,8}, {&quot;one&quot;, &quot;three&quot;, &quot;five&quot;, &quot;eight&quot;}, &quot;no&quot;)<div style="clear:both;"></div>https://community.appian.com/thread/2744?ContentTypeID=1Wed, 05 Jun 2013 19:09:09 GMTd3a83456-d57b-489c-a84c-4e8267bb592a:043a249a-4515-424e-950e-131bfe78b222Mike Schmittthat appears to work, thanks a bunch.<div style="clear:both;"></div>https://community.appian.com/thread/2742?ContentTypeID=1Wed, 05 Jun 2013 18:49:17 GMTd3a83456-d57b-489c-a84c-4e8267bb592a:20e9724a-630d-480a-80b8-aa4dcef430edmoritzwI just had the same requirment. I did the following. I create one rule with:<br />where(ri!array=value,-1) // value being a single value<br />and another one that is using apply:<br />=apply(rule!GetIndexOfArrayWithValue,ri!values,ri!array) //values and array are both multiple<br /><br />not sure wether this is the most efficient way, but I didn&#39;t come up with anything better.<div style="clear:both;"></div>