None of these alternatives gained much traction. The alternatives which involve square brackets only serve to make it obvious that the decorator construct is not a list. They do nothing to make parsing any easier. The '<...>' alternative presents parsing problems because '<' and '>' already parse as un-paired. They present a further parsing ambiguity because a right angle bracket might be a greater than symbol instead of a closer for the decorators.

Now, assume one also desires the ability to add borders to windows. Again, the original Window class has no support. The ScrollingWindow subclass now poses a problem, because it has effectively created a new kind of window. If one wishes to add border support to many but not all windows, one must create subclasses WindowWithBorder and ScrollingWindowWithBorder etc. This problem gets worse with every new feature or window subtype to be added. For the decorator solution, we simply create a new BorderedWindowDecorator—at runtime, we can decorate existing windows with the ScrollingWindowDecorator or the BorderedWindowDecorator or both, as we see fit. Notice that if the functionality needs to be added to all Windows, you could modify the base class and that will do. On the other hand, sometimes (e.g., using external frameworks) it is not possible, legal, or convenient to modify the base class.


The oldest known paintings are at the Grotte Chauvet in France, which some historians believe are about 32,000 years old. They are engraved and painted using red ochre and black pigment, and they show horses, rhinoceros, lions, buffalo, mammoth, abstract designs and what are possibly partial human figures. However, the earliest evidence of the act of painting has been discovered in two rock-shelters in Arnhem Land, in northern Australia. In the lowest layer of material at these sites, there are used pieces of ochre estimated to be 60,000 years old. Archaeologists have also found a fragment of rock painting preserved in a limestone rock-shelter in the Kimberley region of North-Western Australia, that is dated 40,000 years old.[7] There are examples of cave paintings all over the world—in Italy, France, Spain, Portugal, China, Australia, Mexico,[8] etc. In Western cultures, oil painting and watercolor painting have rich and complex traditions in style and subject matter. In the East, ink and color ink historically predominated the choice of media, with equally rich and complex traditions.
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