michael@0: // set.add(v) increments set.size iff the set did not already contain v.
michael@0: 
michael@0: var s = Set();
michael@0: for (var i = 0; i < 10; i++) {
michael@0:     assertEq(s.size, i);
michael@0:     s.add(i);
michael@0: }
michael@0: for (var i = 0; i < 10; i++) {
michael@0:     assertEq(s.size, 10);
michael@0:     s.add(i);
michael@0: }