michael@0: function foo(x, j, n) {
michael@0:   var a = 0;
michael@0:   for (var i = 0; i < n; i++)
michael@0:     a += x[j];
michael@0:   return a;
michael@0: }
michael@0: 
michael@0: var a = foo([1,2,3,4], 3, 100);
michael@0: assertEq(a, 400);
michael@0: 
michael@0: var b = foo([1,2,3,4], 5, 100);
michael@0: assertEq(b, NaN);