> Not in this context they don't. What context is it exactly where they don't matter? I can tell you in practice, in the real world, they very much do. > The

> Not in this context they don't. What context is it exactly where they don't matter? I can tell you in practice, in the real world, they very much do. > They are useless if you want to ensure that a given number is a prime number. It's not useless. The point is that once you have type `PrimeNumber` that can only be constructed after being validated, you then can write functions exist in a reality where only PrimeNumber exists.