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

by throwaway7645 • 10 years ago

150 49 10 years ago

mr_luc• 10 years 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).

evincarofautumn17• 10 years 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.

throwaway764510• 10 years 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.

evincarofautumn17• 10 years 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The site is pretty far out of date—it describes an older version of the language/compiler, so it’s better to check out the GitHub repo[1].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

nothrabannosir• 10 years 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?

evincarofautumn17• 10 years 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• 10 years ago

If the number of stargazers was relatively low, you could @mention everyone in an issue.

detaro• 10 years 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?)

evincarofautumn17• 10 years 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.

throwaway764510• 10 years ago

Thanks for jumping on this (I submitted it after reading it on Reddit awhile back). I like the concept of Forth, but getting started is daunting and JonesForth just isn't enough. Kitten does seem pretty neat for sure and it probably wouldn't be too hard to get into like Haskell and Forth are. I'd love to use a lightweight stack/functional/imperative language if it compiles to native code and is fairly fast. Would it be possible to build someone an .exe or binary and have them run it without any runtime?

evincarofautumn17• 10 years ago

Thanks! Codegen isn’t done in the new compiler, but yes, the goal is to compile to native, statically linked executables, much like Go does. Ideally we wouldn’t even incur a libc dependency, but malloc is just so damn convenient.

You might also give Gforth a try. https://www.gnu.org/software/gforth/

jdmoreira• 10 years ago

Great project! I've been thinking a lot about concatenive languages lately. I haven't had the time to run it or look at the compiler code, I'll do it tomorrow.

I'm curious about how it compares to Joy, is it also homoiconic?

I'm also curious about how you implement the ffi to C.

I might try to contribute :)

evincarofautumn17• 10 years ago

I wouldn’t call it homoiconic, but I’m working on a macro system which will let you manipulate terms as regular data structures at compile time. That was an early insight about Kitten—things are much easier to statically type if you differentiate data from code, and you can recover a lot of the flexibility with other approaches to metaprogramming.

In the old compiler, there was no FFI. In the new compiler, codegen isn’t done yet, but the Kitten ABI on x86-64 is similar enough to the System V ABI that you can just save some registers and do a regular call. As for the front-end, it’s been a long-standing goal to allow a programmer to just import C headers, rather than write or generate a bunch of tedious FFI declarations; I have a prototype implementation of this.

If you’re interested, shoot me an email (username@gmail) and we can find something for you to work on. There are many different things to do: adding features, improving error messages, polishing the interactive environment, writing tests and documentation, integrating with editors, you name it.

dominotw• 10 years ago

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. :)

I remember reading somewhere that Haskell is particularly suited for building compilers. I use Elm at work which is another wonderful language written in Haskell. Has that been your experience ? curious what makes is so great. Any recommendations on resources to learn compiler building in haskell ?

evincarofautumn17• 10 years ago

Yeah, I’ve found Haskell a pleasure to work with for writing compilers. There’s no single thing, just a combination of language features and libraries. The bulk of a compiler is transforming trees of stuff, which Haskell makes very easy, and it nudges you pretty strongly in the direction of making code testable and refactorable.

I don’t have any particular recommendations. Mostly I’ve just been figuring things out as I go along, reading papers and asking for help. I’d written compilers & interpreters before, but got into using Haskell for it with Write Yourself a Scheme[1]. I’ve also heard good things about Implementing a JIT Compiled Language with Haskell and LLVM[2].

[1] https://en.wikibooks.org/wiki/Write_Yourself_a_Scheme_in_48_...

[2] http://www.stephendiehl.com/llvm/

lacampbell3• 10 years ago

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

evincarofautumn17• 10 years 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).

lacampbell3• 10 years 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

murbard2• 10 years 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

evincarofautumn17• 10 years 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• 10 years 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?

evincarofautumn17• 10 years 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• 10 years 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.

evincarofautumn17• 10 years 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. :)

throwaway764510• 10 years ago

Really strange question about your username, but you're not a EE are you?

innocentoldguy• 10 years ago

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

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

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