"David G. Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> writes:
> I'll agree that the description could discuss the case explicitly, and the
> array||scalar case could be added to the examples.
Yeah, the documentation completely fails to explain what happens
when the inputs aren't two arrays or two objects. I'd kind of assumed
that that's an error, but it isn't. Some experimentation indicates
that the behavior in all cases except two objects is to convert any
non-array input to a one-element array, reducing the situation to the
two-array case.
regards, tom lane