michael@0: var a = [];
michael@0: var count = 0;
michael@0: a.valueOf = function() {
michael@0:     ++count;
michael@0: }
michael@0: function f(a) {
michael@0:     6 - a;
michael@0: }
michael@0: 
michael@0: f(3);
michael@0: for (var i=0; i<10; i++)
michael@0:     f(a);
michael@0: 
michael@0: assertEq(count, 10);