dafny

Most PLs don't take off. Language choice is mostly dependent of social factors that can be summarised as "network effect". In PLs that manifests itself primarily through a lack of mature and numerous libraries. Eiffel had additional technical flaws: - Subtyping was wrong. - Handling of concurrency was wrong, in the sense that almost all concurrency was hidden, instead of exposed. Eiffel was an anti-Erlang in this regard. - A lot of modern PL features were missing, e.g. pattern matching, first-class higher-order functions. - The single most distinctive of Eiffel's features, built-in support for assertions, was not supported by good-enough tools. I would argue that the last point is still the case today for all formal verification, see e.g. Microsoft's Dafny [1]. Automating formal verification so that normal programmers can

To throw another one onto the _have you looked at X_ pile, Microsoft Research has put a lot of effort into the Why3 theorem proving platform, which is the backend for the verifier built into their (experimental?) verifier-aware, imperative language, Dafny[1]. It feels very much like writing C#/Java but with verified pre/post conditions, loop invariants etc. I took a formal verification course in college that involved writing several verified sorting, search etc. algorithms in Dafny [2]. I remember it being somewhat cumbersome to write your assertions in a way that the checker can check them, but it's looks very much like what you're suggesting. (At the time I didn't realise that not only does the checker check the program, but compiles it into a CLR-compatible binary, hence you'll see equivalent C code for comparison) [1] https://github.c

[Aside: Why do I have the Whiley (http://whiley.org/about/overview/) link marked seen?] I was mildly curious why Graydon didn't mention my current, mildly passionate affair, Pony (https://www.ponylang.org/), and its use of capabilities (and actors, and per-actor garbage collection, etc.). Then, I saw, "I had some extended notes here about "less-mainstream paradigms" and/or "things I wouldn't even recommend pursuing", but on reflection, I think it's kinda a bummer to draw too much attention to them. So I'll just leave it at a short list: actors, software transactional memory, lazy evaluation, backtracking, memoizing, "graphical" and/or two-dimensional languages, and user-extensible syntax." Which is mildly upsetting, given that Graydon is one of my spirit animals for programming languages. On the other hand, his bit on ESC/dependent typing