Hacker News Reader

Comment by eru | Hacker News Reader

Yes, since at least 80s or so. Languages based on Hindley-Milner type system (https://en.wikipedia.org/wiki/Hindley%E2%80%93Milner) are static and nice to work with. E.g. OCaml or Haskell.

I have some professional experience in rewriting Python and Ruby programmes in Haskell. I make the same amount of stupid mistakes in Python as in Haskell. But whereas Python blows up at runtime / test time, in Haskell it's the compiler yelling at me. The nice thing: that's much faster to detect, and also saves me writing about half the tests.

Don't get me wrong, dynamic typing beats inane static typing like C's or Java's. But good static typing beats dynamic typing.

View on HN

I have experience with OCaml, and I don't find its static typing to be nice to work with at all.

I like the final result of safety, and how whole classes of bugs are excluded once I get my OCaml program to compile. But the process of getting my program to compile in the first place is pretty painful and not fun.

Then again, writing endless unit tests in a dynamically typed language like Scheme is not much fun either. But I don't have to write the unit tests until I've written some functional portion of my program (or even the whole thing) and am satisfied with its design and how it works. Then I could add unit tests or even rewrite it in a safe language like OCaml, if I wanted to.

As I said elsewhere in this thread, for fast prototyping and sheer pleasure of programming, I find Scheme very hard to beat.

The soon-to-be-released GHC 7.8 (Haskell) can defer type errors until runtime to allow you run your program even if part of it is broken, and you can also add "holes" in place of an arbitrary expression and the compiler will tell you the type of the expression you need to replace it with (of course, this will explode if run). I suspect GHC's error messages are better than Ocaml's as well.

That's good to know, and gives me extra incentive to learn Haskell some day.

On the Scheme side of things, I've heard that the newish (4.8.0 and up) versions of Chicken can perform flow analysis to catch some type errors at compile time, and optimize based on types.

There's also Typed Racket, and Chicken has a contracts egg that allows procedures to have pre- and post- conditions.

For some years now, I've heard predictions that in the future languages will allow their users to "dial up" or "dial down" safety features on demand. I guess the above features of Scheme and Haskell are some early steps along that path. We live in interesting times.

Actually, -fdefer-type-errors is already in GHC 7.6: http://www.haskell.org/ghc/docs/latest/html/users_guide/defe...

-XTypeHoles will be in GHC 7.8: http://www.haskell.org/haskellwiki/GHC/TypeHoles

I wrote a simple OCaml compiler for a class in college. I particularly enjoyed using different operators for floating-point and integer math — brilliant usability there, really sold me on static types. Haskell does better with its type classes, except my four attempts to understand monads and arrows have, so far, met with rather mixed success.

Static typing has its place in some people's hearts, and I respect that, but saying that dynamic typing has been outdated since the 80s is (1) trolling, and (2) happens to also just be, like, your opinion, man.

If you want to have another go at it, I recommend Learn you a Haskell for Great Good (available online for free at http://learnyouahaskell.com/) for your Haskell learning needs. Don't stress the Monads and Arrows so much. I know what arrows do, but can't spot their applications in practice. And still I get paid for writing Haskell programmes.

Oh, and please excuse my snarky tone. Your ancestor comment seemed to ask for it. Yes, they are, even now, languages around that are even worse. But better ways have been around for ages. A similar example is garbage collection: It, too, has been around since basically the dawn of programming languages, but only made serious inroads into the mainstream in the last decades.

Honestly, Python 2.x's dynamic typing doesn't make the experience of floating-point/integer maths much better.

The value of 3 / x changing depending on whether I pass 2 or 2.0 is the trade-off of the Python approach, and I honestly don't know which I prefer.

I agree. A type system is good if it allows you to express everything you want to express, if not (as in Java), it is a tool for oppression.

Reply on news.ycombinator.com