Can I call a function in another UAL?

Yes. A UAL is just a shared object library (a DLL in MicroSoft Windows), so you must do the following:

1) Export the symbol for the function to be called, using the apc "-e" option, when you build the UAL to be referenced, e.g.,

apc funcdef.apc -e func

or on Windows use the MSVC++ __declspec(dllexport) prefix to identify the routine as something to be exported from a DLL.

2) On Windows, specify the referenced UAL's "lib" file as an input file on the command line when you compile the probe that contains the call to this external reference. To do this, use the "-linker" flag:

apc main.apc -linker funcdef.lib