10 ms·

Kitten – A statically typed, stack-based functional programming language

150 points by throwaway7645 10y ago

mr_luc 10y ago
Factor was a big name in 'modern stack-based languages,' but of course it's pretty dynamic. I gave Factor a couple of dives a few years ago (after walking through jonesforth prior) and it felt surprisingly complete/mature (except for lack of package manager, of course). Given its novelty, I think it'd be lovely if Kitten took a page from some other languages and had a "QuickStart" or "Crash Course" that consisted of side-by-side examples comparing Kitten to Forth or Factor, or even some other more common language like Javascript. (Ie, elixir-lang does this comparison with Erlang on its website, and it can be helpful).
- evincarofautumn 10y ago
  Factor has been a good source of inspiration when designing Kitten, and I would recommend it to people who want to try a concatenative language now. Kitten is not usable for real-world stuff yet—but it’s getting close, and eventually it should be a good alternative to Factor for those of us in the static-types camp. I’m working on an updated tutorial, and I’ll definitely include some comparisons to other languages that people are likely to know, say JavaScript and C. But I still need to find the right balance between illustrative comparisons and standalone descriptions.
  - throwaway7645 10y ago
    I like the concept of Factor and talked to the author awhile back who isn't actively involved anymore. My problem comes from the confusing doc and lack of beginner materials. Just because I can write a simple app in an imperative or OO context doesn't mean I can write functional nevermind efficient concatenative code without help.
    - evincarofautumn 10y ago
      I do hang out with Slava occasionally, and he’s been helpful even if he’s not that into concatenative programming anymore. For better or worse, the current Factor maintainers are focused more on language internals than onboarding new users. Concatenative/compositional programming does require a different way of thinking, which I think is easy to learn but hard to teach.
      - throwaway7645 10y ago
        Understood. Is concatenative programming not especially good for what he is currently interested in?
        erichocean 10y ago
        Last I heard, Slava was working on the Linux kernel at Google.
        evincarofautumn 10y ago
        He’s working on the Swift compiler at Apple these days.
        throwaway7645 10y ago
        That's pretty prestigious.
evincarofautumn 10y ago
Author of Kitten here, happy to answer any questions. The site is pretty far out of date—it describes an older version of the language/compiler, so it’s better to check out the GitHub repo[1]. I figure I’ll send a pre-release announcement to all the stargazers, when the time is right. One of my new year’s resolutions is to work on Kitten every week this year, and release it before the end of the year. I’m also working on a short ebook (“Programming with Kitten”) to serve as the standard tutorial. I could really use help with all this—building and marketing a language is no small task. If you’re interested in contributing, even if you’re not familiar with Haskell or compilers, I’d be glad to help you get involved. :) [1]: https://github.com/evincarofautumn/kitten https://github.com/evincarofautumn/kitten
- nothrabannosir 10y ago
  > I figure I’ll send a pre-release announcement to all the stargazers, when the time is right. Completely tangential: how do you send a message to all stargazers?
  - evincarofautumn 10y ago
    Using the GitHub API, you can get the list of stargazers for a repo, then get the public email (if any) from each of their profiles.
  - Gaelan 10y ago
    If the number of stargazers was relatively low, you could @mention everyone in an issue.
- detaro 10y ago
  > I’ll send a pre-release announcement to all the stargazers please don't, IMHO that is too spammy. (But it is a good point, why does Github have no "get notified of releases" level of watching?)
  - evincarofautumn 10y ago
    I know it’s not ideal, but I can’t think of a better way to directly reach people that have expressed interest. Nim did the same thing, and I’m happy to get the occasional direct update from them. Obviously I’d have to include an “unsubscribe” link or whatever.
ohSoCute 10y ago
Oh great. Another facetiously cute thing on the internet.
lacampbell 10y ago
Parentheses, tuples, for loops... my first impression is it doesn't look very concatenative.
- evincarofautumn 10y ago
  The Levenshtein example isn’t the best. It’s also using an older version of the language with things like mixfix operators (“from()to(){}”) which have since been removed. Anyway, Kitten is concatenative at the term level (all terms denote functions, juxtaposition is composition) but not the token level as in Forth (e.g., “{” and “}” are not meaningful words on their own).
  - lacampbell 10y ago
    Interesting, I am curious as to why you are concatenative at the term level only. Is it trying to make syntax more palatable to ALGOL family programmers? PS: I loved your "why concatenative programming matters" article
    - astrobe_ 10y ago
      Sorry but I have to be negative here because I love Forth. People tried to make Lisp/Scheme less 'prefix', and it didn't fly. People tried to make Forth less 'postfix', and it didn't fly. The whole point of concatenative languages is the simple syntax and implementation. I wrote a Forth dialect in C - actually I wrote many over the years because it's a refinement and adaptation process, but I'll talk about the one I'm currently using. Its core is a little less than 2K SLOC that compile into a ~30Kb (yes, kilobytes) (~60Kb for Windows 32bits) . It uses a very straightforward direct threaded scheme - something like (ip++)() - but that's plenty fast already (think Lua-fast). It's easy to modify because, well, I wrote it from top to bottom. At some point I wish I had separators for number and binary numbers. In an hour or so I could write things like 0b1010_1001. At one point I was tired to write "test.4" load*. I hacked the interpreter so that when it sees a word that ends with ".4" it tries to load the file with that name. Very handy. At some point I wish I could embed my interpreter into a large embedded application to help with debugging. No problem either. It's easy to extend. Need more accurate time stamps? Here you go: static void p_getms(void) { struct timeval t; gettimeofday(&t, NULL); push(t.tv_usec/1000); push(t.tv_sec); } And then you add the function in an array to "register" it, like you do in Lua. I can write bindings to libraries almost on-the-fly thanks to the braindead API which consists mainly in push() and pop(). No FFI required. It's also trivial to translate a piece of code from Forth to C when you need speed. I think it could even be automated. THIS is what Forth is really about. I don't see the point of having people "think concatenative" if they don't have all this in return. You want static typing? I can understand, because Forth is quite unforgiving and will segfault if you make a mistake and that can be annoying. Actually, when I started to write the interpreter I'm currently using, my plan was to write some kind of "linter" to help with that. However as an embedded systems programmer I'm pretty used to printf() debugging (it might be a bad habit) and Forth is pretty good at that because you can invoke a REPL very easily. So I have yet to find the motivation to write that Linter.
murbard2 10y ago
I'm glad to see a successor for the defunct cat. I love the precision and concision you can achieve with this style of programming. Cat was a big inspiration in Michelson, another concatenative, statically typed, functional programming language that we designed to run smart contract in Tezos. http://www.tezos.com/language.txt http://www.tezos.com/language.txt
- evincarofautumn 10y ago
  I hadn’t heard of it—that’s very interesting, thanks. :) It would be nice to use GADTs for Kitten’s AST, but last time I tried, it made inference complicated, and I never figured out a good way to encode Kitten’s permission system in Haskell types. Even just annotating Kitten types with their kinds (in the old compiler) was too cumbersome.
phantom_oracle 10y ago
- What other programming-languages inspired this one? - What market is this language addressing? (ie. where should I "be using it"?) - What is the bus-factor? - How difficult is/was it to write/design your own programming language?
- evincarofautumn 10y ago
  Kitten is inspired mainly by: • Systems languages (C, C++) • Functional languages (Haskell, OCaml) • Concatenative languages (Cat, Factor, Joy, Forth) As a functional language without GC, it’s intended for mid-level applications where you might ordinarily reach for C++, but it remains to be seen how people might actually use it. It might be useful as a lightweight scripting language, or for writing low-level embedded code that feels high-level. The bus factor is currently very bad—people have contributed here and there over the years, but I’m pretty much the only core developer. Building a language is as hard as you make it, basically. You can make a pretty good toy language in a weekend, or you can go all-in and try to create something innovative, elegant, versatile, stable, usable, and performant. That takes years, and it’s a process of discovery with many false starts.
mbrock 10y ago
Kitten seems like a cool project. If I find some free time I might try to contribute something. Somewhat relatedly, I've been fantasizing about a mobile friendly editor for source code, and it's struck me that concatenative languages can be nicely edited by moving tokens around, which should be quite doable on a smartphone. Static typing would make it even better, since the editor could show type errors, predict input, and so on.
- evincarofautumn 10y ago
  That is one of the goals of the project—the simple language structure and static types should let you do some interesting things with program visualisation and editing. Email me (username@gmail) if you’d like to chat about it—maybe we could build something cool together. :)
- throwaway7645 10y ago
  Really strange question about your username, but you're not a EE are you?
innocentoldguy 10y ago
The REPL stack for doing calculations looks interesting (you can find it in the tutorial link: http://kittenlang.org/tutorial/ http://kittenlang.org/tutorial/). I'll have to try it out though to see how well I like it.

150 points by throwaway7645 10y ago

Factor was a big name in 'modern stack-based languages,' but of course it's pretty dynamic. I gave Factor a couple of dives a few years ago (after walking through jonesforth prior) and it felt surprisingly complete/mature (except for lack of package manager, of course). Given its novelty, I think it'd be lovely if Kitten took a page from some other languages and had a "QuickStart" or "Crash Course" that consisted of side-by-side examples comparing Kitten to Forth or Factor, or even some other more common language like Javascript. (Ie, elixir-lang does this comparison with Erlang on its website, and it can be helpful).

evincarofautumn 10y ago
Factor has been a good source of inspiration when designing Kitten, and I would recommend it to people who want to try a concatenative language now. Kitten is not usable for real-world stuff yet—but it’s getting close, and eventually it should be a good alternative to Factor for those of us in the static-types camp. I’m working on an updated tutorial, and I’ll definitely include some comparisons to other languages that people are likely to know, say JavaScript and C. But I still need to find the right balance between illustrative comparisons and standalone descriptions.
- throwaway7645 10y ago
  I like the concept of Factor and talked to the author awhile back who isn't actively involved anymore. My problem comes from the confusing doc and lack of beginner materials. Just because I can write a simple app in an imperative or OO context doesn't mean I can write functional nevermind efficient concatenative code without help.
  - evincarofautumn 10y ago
    I do hang out with Slava occasionally, and he’s been helpful even if he’s not that into concatenative programming anymore. For better or worse, the current Factor maintainers are focused more on language internals than onboarding new users. Concatenative/compositional programming does require a different way of thinking, which I think is easy to learn but hard to teach.
    - throwaway7645 10y ago
      Understood. Is concatenative programming not especially good for what he is currently interested in?
      - erichocean 10y ago
        Last I heard, Slava was working on the Linux kernel at Google.
        evincarofautumn 10y ago
        He’s working on the Swift compiler at Apple these days.
        throwaway7645 10y ago
        That's pretty prestigious.

evincarofautumn 10y ago

Author of Kitten here, happy to answer any questions. The site is pretty far out of date—it describes an older version of the language/compiler, so it’s better to check out the GitHub repo[1]. I figure I’ll send a pre-release announcement to all the stargazers, when the time is right. One of my new year’s resolutions is to work on Kitten every week this year, and release it before the end of the year. I’m also working on a short ebook (“Programming with Kitten”) to serve as the standard tutorial. I could really use help with all this—building and marketing a language is no small task. If you’re interested in contributing, even if you’re not familiar with Haskell or compilers, I’d be glad to help you get involved. :) [1]: https://github.com/evincarofautumn/kitten https://github.com/evincarofautumn/kitten

nothrabannosir 10y ago
> I figure I’ll send a pre-release announcement to all the stargazers, when the time is right. Completely tangential: how do you send a message to all stargazers?
- evincarofautumn 10y ago
  Using the GitHub API, you can get the list of stargazers for a repo, then get the public email (if any) from each of their profiles.
- Gaelan 10y ago
  If the number of stargazers was relatively low, you could @mention everyone in an issue.
detaro 10y ago
> I’ll send a pre-release announcement to all the stargazers please don't, IMHO that is too spammy. (But it is a good point, why does Github have no "get notified of releases" level of watching?)
- evincarofautumn 10y ago
  I know it’s not ideal, but I can’t think of a better way to directly reach people that have expressed interest. Nim did the same thing, and I’m happy to get the occasional direct update from them. Obviously I’d have to include an “unsubscribe” link or whatever.

ohSoCute 10y ago

Oh great. Another facetiously cute thing on the internet.

lacampbell 10y ago

Parentheses, tuples, for loops... my first impression is it doesn't look very concatenative.

evincarofautumn 10y ago
The Levenshtein example isn’t the best. It’s also using an older version of the language with things like mixfix operators (“from()to(){}”) which have since been removed. Anyway, Kitten is concatenative at the term level (all terms denote functions, juxtaposition is composition) but not the token level as in Forth (e.g., “{” and “}” are not meaningful words on their own).
- lacampbell 10y ago
  Interesting, I am curious as to why you are concatenative at the term level only. Is it trying to make syntax more palatable to ALGOL family programmers? PS: I loved your "why concatenative programming matters" article
  - astrobe_ 10y ago
    Sorry but I have to be negative here because I love Forth. People tried to make Lisp/Scheme less 'prefix', and it didn't fly. People tried to make Forth less 'postfix', and it didn't fly. The whole point of concatenative languages is the simple syntax and implementation. I wrote a Forth dialect in C - actually I wrote many over the years because it's a refinement and adaptation process, but I'll talk about the one I'm currently using. Its core is a little less than 2K SLOC that compile into a ~30Kb (yes, kilobytes) (~60Kb for Windows 32bits) . It uses a very straightforward direct threaded scheme - something like (ip++)() - but that's plenty fast already (think Lua-fast). It's easy to modify because, well, I wrote it from top to bottom. At some point I wish I had separators for number and binary numbers. In an hour or so I could write things like 0b1010_1001. At one point I was tired to write "test.4" load*. I hacked the interpreter so that when it sees a word that ends with ".4" it tries to load the file with that name. Very handy. At some point I wish I could embed my interpreter into a large embedded application to help with debugging. No problem either. It's easy to extend. Need more accurate time stamps? Here you go: static void p_getms(void) { struct timeval t; gettimeofday(&t, NULL); push(t.tv_usec/1000); push(t.tv_sec); } And then you add the function in an array to "register" it, like you do in Lua. I can write bindings to libraries almost on-the-fly thanks to the braindead API which consists mainly in push() and pop(). No FFI required. It's also trivial to translate a piece of code from Forth to C when you need speed. I think it could even be automated. THIS is what Forth is really about. I don't see the point of having people "think concatenative" if they don't have all this in return. You want static typing? I can understand, because Forth is quite unforgiving and will segfault if you make a mistake and that can be annoying. Actually, when I started to write the interpreter I'm currently using, my plan was to write some kind of "linter" to help with that. However as an embedded systems programmer I'm pretty used to printf() debugging (it might be a bad habit) and Forth is pretty good at that because you can invoke a REPL very easily. So I have yet to find the motivation to write that Linter.

murbard2 10y ago

I'm glad to see a successor for the defunct cat. I love the precision and concision you can achieve with this style of programming. Cat was a big inspiration in Michelson, another concatenative, statically typed, functional programming language that we designed to run smart contract in Tezos. http://www.tezos.com/language.txt http://www.tezos.com/language.txt

evincarofautumn 10y ago
I hadn’t heard of it—that’s very interesting, thanks. :) It would be nice to use GADTs for Kitten’s AST, but last time I tried, it made inference complicated, and I never figured out a good way to encode Kitten’s permission system in Haskell types. Even just annotating Kitten types with their kinds (in the old compiler) was too cumbersome.

phantom_oracle 10y ago

- What other programming-languages inspired this one? - What market is this language addressing? (ie. where should I "be using it"?) - What is the bus-factor? - How difficult is/was it to write/design your own programming language?

evincarofautumn 10y ago
Kitten is inspired mainly by: • Systems languages (C, C++) • Functional languages (Haskell, OCaml) • Concatenative languages (Cat, Factor, Joy, Forth) As a functional language without GC, it’s intended for mid-level applications where you might ordinarily reach for C++, but it remains to be seen how people might actually use it. It might be useful as a lightweight scripting language, or for writing low-level embedded code that feels high-level. The bus factor is currently very bad—people have contributed here and there over the years, but I’m pretty much the only core developer. Building a language is as hard as you make it, basically. You can make a pretty good toy language in a weekend, or you can go all-in and try to create something innovative, elegant, versatile, stable, usable, and performant. That takes years, and it’s a process of discovery with many false starts.

mbrock 10y ago

Kitten seems like a cool project. If I find some free time I might try to contribute something. Somewhat relatedly, I've been fantasizing about a mobile friendly editor for source code, and it's struck me that concatenative languages can be nicely edited by moving tokens around, which should be quite doable on a smartphone. Static typing would make it even better, since the editor could show type errors, predict input, and so on.

evincarofautumn 10y ago
That is one of the goals of the project—the simple language structure and static types should let you do some interesting things with program visualisation and editing. Email me (username@gmail) if you’d like to chat about it—maybe we could build something cool together. :)
throwaway7645 10y ago
Really strange question about your username, but you're not a EE are you?

innocentoldguy 10y ago

The REPL stack for doing calculations looks interesting (you can find it in the tutorial link: http://kittenlang.org/tutorial/ http://kittenlang.org/tutorial/). I'll have to try it out though to see how well I like it.