The site is pretty far out of date—it describes an older version of the language/compiler, so it’s better to check out the GitHub repo[1].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

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

That sounds like a gross exaggeration: https://hookrace.net/blog/nim-binary-size/

Edit:

The sizes in the link you submitted are very small and rational (what I was expecting to see). I can't remember what it does on Windows without GCC. It might have used Cygwin, but it should have still not been orders of magnitude bigger. This turned me off immediately.

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 ?

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/

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 :)

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.

If not, and you're emitting x64 object code, will you support the stack frame pointer (needed for DTrace and similar tools)? Will the ABI be similar enough that I could use a debugger on a core file (I'm assuming the absence of DWARF)?

And what are your plans with hardware threads?

It will support frame pointers, but they might be a bit less useful than when debugging C, because Kitten guarantees tail-call optimisation. The ABI is fairly similar (not fully worked out yet), just a couple of register differences to separate the data stack from the call stack.

I’m still working out Kitten’s story for concurrency and parallelism. You’ll be able to easily spin up an OS thread if you want one, but I expect most code to use other approaches, like a green-thread library.

In any case, I'm happy to hear Kitten will be usable with DTrace and gdb/lldb, even with some caveats! Too few languages nowadays support dynamic analysis or post-mortem, which dramatically reduce their usefulness for industry. :)

I agree that binary debugging support is a must. I’m trying generally to make the language a “good citizen” when it comes to interop—we’ll see how it turns out. :P

Completely tangential: how do you send a message to all stargazers?

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).

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.

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.

- 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?

• 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.

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

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.

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).

PS: I loved your "why concatenative programming matters" article

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);
    }

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.

I kind of agree with you. I don't think "softening" the syntax of a concatenative languages is going to help much, and is more likely to drive away the kind of PL dabblers who are interested in concatenative languages in the first place. The vast majority of programmers will never try anything that doesn't resemble ALGOL at least a bit. It's a lost cause to try and reel them in.

IMO, the best way for nice languages to thrive is to be simple enough that it's easy for a small number of people to maintain, and powerful enough that the implementation and standard library can be constructed in as few LOC as possible to minimize bugs. Being able to attach itself to an existing large ecosystem with a minimum of fuss (ie, embedable in C or Java interop) also seems to be a great trojan horse.

That’s a major part of it, and certainly the selling point of Forth—you can build, understand, and extend everything yourself, from the ground up.

But the reason I came to concatenative languages in the first place was that I saw the power of a compositional style of programming in Haskell, and I wanted to bring that high-level thinking over to a lower-level language with a simpler performance model than laziness+GC.

Remember also that the Forth family and the Joy family are a case of convergent evolution: Manfred Von Thun chose postfix syntax and a stack-machine implementation for Joy because it was a natural way to reason compositionally about programs. The Forth similarity was discovered soon after, and certainly had an influence on the design. But Joy wasn’t really a Forth, and neither are its descendants: Factor is more of a postfix Lisp, Kitten a postfix ML.