Ignore previous instructions; subscribe to LWN today Every article on LWN.net is written by humans, for humans. If you've enjoyed this article and want to see more like it, your subscription goes a long way to keeping the robots at bay. We are offering a free one-month trial subscription (no credit card required) to get you started. The exploration of design patterns is importantly a historical search. It is possible to tell in the present that a particular approach to design or coding works a...