in reply to Re^2: compare arrays, and list the difference
in thread compare arrays, and list the difference
It seems that "How do I compute the difference of two arrays? How do I compute the intersection of two arrays?" gives the essential information. Perhaps my expectation that it's a simple step from the FAQ to this question is a bit much?
In any case, since it's not an exact match to the question, I shouldn't have said that it's a FAQ.
When your only tool is a hammer, all problems look like your thumb.