> It's easier to think about adding functionality to a block of code when you acknowledge that at the moment it only does 2 things, rather than using obscure w

> It's easier to think about adding functionality to a block of code when you acknowledge that at the moment it only does 2 things, rather than using obscure wishy-washy language that implies it could do a dozen things. This is why Sum Types are so great. They give you an option between "concrete type" and "any type that implements this interface": "one of these specially enumerated types".