michael@0: function isnan(n) { return n !== n }
michael@0: 
michael@0: function f(x) {
michael@0:     var sum = 0;
michael@0:     for (var i = 0; i < 100; ++i)
michael@0:         sum += x.x;
michael@0:     return sum;
michael@0: }
michael@0: var o = {};
michael@0: assertEq(isnan(f(o)), true);
michael@0: o.x = 1;
michael@0: assertEq(f(o), 100);
michael@0: var o = {a:1, b:2};
michael@0: assertEq(isnan(f(o)), true);
michael@0: o.x = 2;
michael@0: assertEq(f(o), 200);
michael@0: 
michael@0: function g(x) {
michael@0:     var sum = 0;
michael@0:     for (var i = 0; i < 100; ++i)
michael@0:         sum += x.x;
michael@0:     return sum;
michael@0: }
michael@0: var o = {c:1, x:1};
michael@0: assertEq(g(o), 100);
michael@0: var o = {};
michael@0: assertEq(isnan(g(o)), true);
michael@0: 
michael@0: function h(x) {
michael@0:     var sum = 0;
michael@0:     for (var i = 0; i < 100; ++i)
michael@0:         sum += x.x;
michael@0:     return sum;
michael@0: }
michael@0: 
michael@0: var proto1 = {};
michael@0: var proto2 = Object.create(proto1);
michael@0: var o = Object.create(proto2);
michael@0: assertEq(isnan(f(o)), true);
michael@0: assertEq(isnan(g(o)), true);
michael@0: assertEq(isnan(h(o)), true);
michael@0: proto2.x = 2;
michael@0: assertEq(f(o), 200);
michael@0: assertEq(g(o), 200);
michael@0: assertEq(h(o), 200);
michael@0: var o = {}
michael@0: assertEq(isnan(f(o)), true);
michael@0: assertEq(isnan(g(o)), true);
michael@0: assertEq(isnan(h(o)), true);