> What software issue does category theory and abstract algebra solve? They address (not solve) the problem of lack of code reuse. I have never seen a languag

> What software issue does category theory and abstract algebra solve? They address (not solve) the problem of lack of code reuse. I have never seen a language where I can put to use so much code written elsewhere without knowledge of my particular use case. They also address the problem of reasoning about the behaviour of code being difficult.