Comment by oftenwrong

Sure, monads provide an elegant way to structure code with error conditions, but I don't see a problem with using simple assertions, throws, try-catch to enforce invariants. Personally, I don't care about elegance as much as whether or not it works, as long as it is simple to use and maintain. I can return something like a Maybe/Either, or I can throw an exception - both approaches are fine by me if it forces the programmer to account for error cases.