A user reported an error to me that I've seen a few times recently. His code was doing something like this:

<cfset fleet = arrayAppend(fleet, "Star Destroyer: Wrath of Elmo")>

Later on he did...

<cfloop index="x" from="1" to="#arrayLen(fleet)#">

His error said that he was trying to use a boolean as an array. Where did the error come from?

The arrayAppend function, like a few other ColdFusion functions, return true or false, not the changed data structure. Personally I'm not sure why as I don't know a situation where it would return false.

As another reminder - for functions like these you do not need to actually store the result:

<cfset result = arrayAppend(heroes, "Forge")>

But can instead simply use a shorthand statement:

<cfset arrayAppend(heroes, "Forge")>