We've all written code like this: class Foo method bar(x) switch x case even? case odd? This is closed. What if I want to

We've all written code like this: class Foo method bar(x) switch x case even? case odd? This is closed. What if I want to add a new case without modifying this class? I could subclass but then I have to know a lot about how Foo works. Perhaps bars has assumptions about whether it needs to run before or after I run my subclassed version, and on and on. This kind of nastiness pervades too much code. method bar Foo even?(x) method bar Foo odd?(x) ... As far as logic programming - I think the paradigm is so little known that people fail to see how useful it is. Yet many non-trivial programs use ... relational databases! How would you even begin to express the following idea in JavaScript? http://stackoverflow.com/questions/6713424/how-do-i-express-this-logic/6719627#6719627 http://stackoverflow.com/questions/6713424/how-do-i-express-... Note that the idea is actually quite simple and useful! Another example is to produce all words that form a specific telephone number: https://gist.github.com/1107653 https://gist.github.com/1107653 Of particular interest is the encode function, the relevant bit: (run* [q] (exist [x y xo yo] (appendo x y s) ;; infer all possible lists that could concat ;; to form s (wordo x xo) (wordo y yo) ;; convert to words (project [xo yo] (== q (apply str xo yo)))) ;; create the combined string Note I don't have to mention indices, for loops, list comprehensions or any other iterative machinery. All the other solutions I saw had a lot of boilerplate to express this simple idea of inferring the lists that could be concatenated to form s.