.ocompare
(for "outer compare") returns a matrix whose (i,j)th
element is TRUE if x[i] is identical to y[j], and FALSE otherwise. .asym_compare
calls .ocompare
and iterprets its result
asymmetrically. Elements of x
that are not in y
ae
considered "new". Similarly, Elements of y
that are not in
x
ae considered "removed". Elements that are in both are
"common".
Todo: check if the above is correct or the other way round! !!!