Re: A couple of questions about goops method parameters
Taylan Ulrich Bayirli/Kammer taylanbayi...@gmail.com writes: Panicz Maciej Godek godek.mac...@gmail.com writes: [...] it's hard for me to see the advantage of FRP over OOP in practical systems (e.g. windowed applications with buttons and so on). [...] An off-topic remark: I don't know about *functional* reactive programming but from my experience so far as an iOS developer, I've been *longing* for a reactive programming system that automates state changes even if not fully hiding them. It would be invaluable being able to say button2.leftEdge = button1.rightEdge + 20px and have this equation be held automatically on changes to the layout of button1 (which might happen because it itself reacts to other layout changes), or to be able to say button.disabled = condition1 or condition2 and have the disabled status of button update automatically as the truthiness of the conditions changes. (The former use-case is actually covered by layout constraints, but that's strictly limited to layouting.) IIRC, Metafont does that; but obviously it isn't intended as a general language. Are there more general languages that solve equations like this? Regards, Neil
Re: A couple of questions about goops method parameters
Neil Jerram n...@ossau.homelinux.net writes: IIRC, Metafont does that; but obviously it isn't intended as a general language. Are there more general languages that solve equations like this? From what I know, Prolog. Other than that, Scheme. ;) Apart from David's FRP implementation, I worked on the following a little: https://gitorious.org/taylan-guile/reactive/ (Warning: I might force-push commits to that repo at times. It's not ready for consumption.) I don't consider it complete, and it might be broken. Some simple examples work: guile ,use (reactive base) guile (define x 0) guile (define v (make-value () x)) guile (define v2 (make-value (v) (display recalculated\n) (+ v 5))) guile (get/tainted v2) recalculated $2 = 5 guile (get/tainted v2) $3 = 5 guile (set! x 1) guile (taint! v) guile (get/tainted v2) recalculated $4 = 6 guile As you see, it's not purely-functional, and it requires explicit tainting of root values. After that, though, requesting any value which directly or indirectly depends on that root will ignite a recalculation of the graph of dependent values up to the requested one. I continuously get confused while trying to reason about the precise behavior of this system (even though it's very small), and had grave bugs in it at times (actually I just fixed one while writing this because I did a wholesale clean-up on the repo and re-uploaded it at the above link). Therefore, please don't trust that module for real usage. Taylan
Re: A couple of questions about goops method parameters
Marko Rauhamaa ma...@pacujo.net writes: It's perfectly fine to avoid errors by generalizing semantics so I wouldn't mind if you did what you propose. However, the dynamic type system is necessary for the simple fact that you will need to define runtime semantics. Oh, I was rather looking at things from a low-level perspective. E.g. the foo string in my example was meant as a pointer, whose numeric value plus 5 resulted in an integer whose underlying byte sequence is then interpreted as an IEEE double. In other words I was suggesting that by default there are only byte sequences, and type systems help to work with these conveniently. No, the primary objective is not to prevent errors but to have well-defined semantics. Scheme, Python, C or Java would function perfectly well without any type error checking, static or dynamic. The results could be undefined or a burning computer, that doesn't matter. What matters is that you know what a well-defined program is supposed to do. I think I understand your viewpoint, and it also makes sense: types might not be essential to bit-crunching, but they are to abstract models of computation. However, in my extensive practical experience, a static type system, [...] Does that experience cover languages like SML, Ocaml, and Haskell? (Not a rhetorical question, though I suspect it doesn't; at least not as much as languages like C, C++, and Java.) Taylan
Re: A couple of questions about goops method parameters
Taylan Ulrich Bayirli/Kammer taylanbayi...@gmail.com: Marko Rauhamaa ma...@pacujo.net writes: However, in my extensive practical experience, a static type system, [...] Does that experience cover languages like SML, Ocaml, and Haskell? I have had superficial experience with SML way back (late 80's). No idea how the languages would work in practice. However, I don't feel I'm missing anything in Scheme. (Not a rhetorical question, though I suspect it doesn't; at least not as much as languages like C, C++, and Java.) Not anywhere near as much. What do you have to say about those languages? Marko
Re: A couple of questions about goops method parameters
Marko Rauhamaa ma...@pacujo.net writes: Not anywhere near as much. What do you have to say about those languages? Just what I said previously: many users of languages with more sophisticated static type systems like Ocaml or Haskell say they prefer that over dynamic typing. I don't have much experience myself, though at times I also felt positive about the ability to encode some logic in a static type system. Taylan
