[codebje]

Much of software design is about composition, which is where category theory shines, just at the most shallow levels.

If I dream up a way to tackle a problem, have I made a category? If I have two modules, can I compose them into one, is there an initial or final module, is composition associative? If there's some underlying structure, what's the free module based on it?

Those questions can help make more durable designs.