How else would you write software with modular and re-usable components? Hah! However you want! The first few chapters of Paul Graham's `On Lisp' does a great

How else would you write software with modular and re-usable components? Hah! However you want! The first few chapters of Paul Graham's `On Lisp' does a great job covering closures, which can provide elegant encapsulation. But even in Java or C++, objects aren't the only modular or reusable components - consider packages or name spaces, for example. Data types such as streams, arrays, and trees don't have to be classes, either - take a look at Haskell's data types.