michael@0: actual = '';
michael@0: expected = '3,6,9,12,15,18,';
michael@0: 
michael@0: function slice(a, b)
michael@0: {
michael@0:   //return { x: a + ':' + b };
michael@0:   return b;
michael@0: }
michael@0: 
michael@0: function f(index)
michael@0: {
michael@0:   var length = 20;
michael@0: 
michael@0:   function get3() {
michael@0:     //appendToActual("get3 " + index);
michael@0:     if (length - index < 3)
michael@0:       return null;
michael@0:     return slice(index, index += 3);
michael@0:   }
michael@0: 
michael@0:   var bytes = null;
michael@0:   while (bytes = get3()) {
michael@0:     appendToActual(bytes);
michael@0:   }
michael@0: }
michael@0: 
michael@0: f(0);
michael@0: 
michael@0: 
michael@0: assertEq(actual, expected)