> Is this something professional programmers are having trouble with?? I would say, yes. So does everybody else. If you don't believe it, I don't think you app

> Is this something professional programmers are having trouble with?? I would say, yes. So does everybody else. If you don't believe it, I don't think you appreciate the depth of these problems. I am reminded of Eric Meijer saying that the interface (in the Java sense) part of the contract between types is the least interesting part. What is important are their algebraic properties, which can be modeled using functional types and other bunch of advanced type-theoretical ideas (like linear types for instance). Modelling stuff with types is not easy, it's an art.