Subdiagram Calls (Custom Subroutines)

In addition to the practically fix set of built-in functions and procedures listed in the previous section, you may also execute available Nassi-Shneiderman diagrams of type subroutine as functions or procedures. But whereas the built-in functions may arbitrarily be used as part of appropriate expressions in all kinds of elements and built-in procedure reference statements in regular Instruction elements, this does not hold if you want to call subroutine diagrams.

Their execution will only work if placed within a Call element (and it must adhere to a very restrictive syntax, moreover, see Call). In order to be found on execution, custom subroutine diagrams must have been parked in the Arranger before (unless it's a recursive call, then it finds "itself" in the Structorizer work area). If Executor does not find a called subroutine, then execution will abort with an error message like this:

If custom subroutines are executed as top-level diagrams for debugging purposes then the Executor will simulate the call by asking the user for the value of every argument (as if there were input statements at the beginning) and will present the result value in a message box (or a scrollable list view, if the result value is an array or record).