> The usefulness of types is in them describing the input/output dependencies in your code. I agree, but I find types way too weak in that respect. Its not eno

> The usefulness of types is in them describing the input/output dependencies in your code. I agree, but I find types way too weak in that respect. Its not enough to know a function accepts ints; I want to know its range as well. I spent so many weeks hunting down overflow and out-of-range errors and null pointer exceptions that types feel like an illusion of robustness at best. > Now, how will immutability, hostility to state or unit testing help you with this question? Not that much, I'll give you that. But the same is true for a function whose range was 1-20 being refactored into a range of 1-10; types won't catch that. I used to like types, then testing, now I'm looking at specifications I can write once, compose and then generate assertions, documentation, test data and everything else from. Its by far the best ROI of the three.