[feeley]

The Ribbit compiler was developed using Gambit but most of the code is portable. I rewrote a few parts with cond-expand to port rsc.scm to older versions of Gambit and also Guile and Chicken. If you pull the latest commit the Ribbit system should work with any of those Scheme systems. The README also contains usage instructions, here is a relevant part:

The Ribbit compiler is written in Scheme and can be executed with Gambit, Guile or Chicken. It has been tested with Gambit v4.7.5 and above. For the best experience install Gambit from https://github.com/gambit/gambit .

Currently Ribbit supports the target languages C, JavaScript, Python and Scheme which are selectable with the compiler's `-t` option with `c`, `js`, `py`, and `scm` respectively. The compacted RVM code can be obtained with the target `none` which is the default.

The `-m` option causes a minification of the generated program. This requires a recent version of Gambit.

The `-l` option allows selecting the Scheme runtime library (located in the `lib` subdirectory). The `min` library has the fewest procedures and a REPL that supports the core Scheme forms only. The `max` library has most of the R4RS predefined procedures, except for file I/O. The `max-tc` library is like `max` but with run time type checking. The default is the `max-tc` library.

Here are a few examples:

    Use Gambit to compile the minimal REPL to JavaScript
    and execute with nodejs:

      % cd src
      % gsi rsc.scm -t js -l min repl-min.scm
      % echo "(define f (lambda (n) (if (< n 2) n (+ (f (- n 1)) (f (- n 2))))))(f 25)" | node repl-min.scm.js
      > 0
      > 75025
      >

[throwaway81523]

Thanks, I did get the C, Python, and Scheme RVM's to work. I just didn't realize that (define (f x) ...) didn't work as I was used to. I didn't get JS working because it required a JS build tool that I didn't have installed. I didn't pursue it as I don't use JS much.

Can I ask how long "gsi rsc.scm..." took in your example? It ran for around an hour when I tried it with python output. I then stopped it and compiled rsc.scm with gsc and that took just a fraction of a second to build the repl's.

Do you have particular applications in mind for Ribbit? I see some general mentions of running it in browsers and email clients, but those tend to have JS already available.

Finally, I'm wondering if you think that functional-style programming (avoiding mutation) inherently uses more ram than a more mutation-heavy style. I'm asking because Micropython is fairly usable with 32k of ram and has been shoehorned into 16k (BBC micro:bit v1), but Hedgehog and apparently Ribbit both want around 200k. Hedgehog relies on bytecode and an offline AOT compiler but Micropython has a REPL.

[feeley]

It is almost instantaneous:

    % /usr/bin/time gsi rsc.scm -t c -l min repl-min.scm
            0.06 real         0.05 user         0.00 sys
    % gcc -O3 repl-min.scm.c
    % echo "(define f (lambda (n) (if (< n 2) n (+ (f (- n 1)) (f (- n 2))))))(f 25)" | /usr/bin/time ./a.out
    > 0
    > 75025
    >
            0.10 real         0.10 user         0.00 sys

My guess is that you were using an old version of Gambit (before I added the support for older versions of Gambit).

The work on Ribbit is not driven by a specific application. It started as a challenge to write the smallest footprint implementation of Scheme after being inspired by the "sectorlisp" system (which has now reached an amazing milestone of just 0.5 KB!). However sectorlisp doesn't have a GC, continuations, tail-calls, etc so the comparison is a bit apples-to-oranges.

The main advantages of the RVM are its small size and its portability. This is particularly useful for code mobility. The exact same Scheme code can run on the desktop, in the browser, on the web server, on a microcontroller, an Excel spreadsheet, a shell script, etc etc And because continuations are a good way to represent the state of a running process I foresee applications where a running program migrates easily from one environment to the other by serializing the continuation (a game running in your desktop browser could be migrated to the browser on your phone to continue playing on the subway ride back home).

Concerning "functional-style programming (avoiding mutation) inherently uses more ram than a more mutation-heavy style" it greatly depends on how smart your compiler is. A smart one can in some cases generate the same code. An example that comes to mind is a tail-recursive function that adds numbers from a list. The functional program has no mutations but a compiler doing TCO can generate the same code as an imperative program that uses mutations.

[throwaway81523]

Ah, thanks for all that, and I will try the new version of gambit. I don't remember for certain whether the looping I encountered was with the old version. It will be cool if Ribbit can become completely self-hosting.

I do know there have been some web sites (including I think HN) written in Scheme, that originally used continuations as sessions, but ended up switching away from that approach once things got more complicated. It's a cool idea though.

Ribbit reminds me of this article mentioning "Fluchtpunkt Lisps", in case you're not familiar with it: http://blog.fogus.me/2011/05/03/the-german-school-of-lisp-2/

I guess it is an example of one.

Ribbit seems more interesting to me than Sectorlisp because of the issues you mention! I'll keep playing with it. Even if I don't find direct uses for it, its implementation methods are worthy of study.

I've been wanting for a while to make a Hedgehog Lisp back end for Purescript (purescript.org). Ribbit might be another interesting target.

Added: I think the Ribbit REPL needs some kind of exception trap. Otherwise saying something like (3) crashes the whole interpreter, which is not so great for an interactive environment.

Hedgehog has built-in functional AVL trees that substitute for hash tables, arrays, and other lookup structures. They are very useful, but are an example of functional style possibly requiring more ram than imperative style where you can mutate stuff.