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1 point by akkartik 153 days ago | link | parent | on: How portable is Arc?

It's not really, out of the box.

Thanks! I'll check this out later.
2 points by krapp 251 days ago | link | parent | on: Why Bel after Arc

From what I can tell from the introduction[0] and initial HN thread[1] Bel is an academic exercise in developing a programming language by focusing on axioms rather than implementation. Also:

    I think the point of a high-level language is to make your programs shorter. All other things (e.g. libraries) being equal, language A is better than language B if programs are shorter in A. (As measured by the size of the parse tree, obviously, not lines or characters.) The goal of Bel is to be a good language. This can be measured in the length of programs written in it.
Make of that what you will.



Join the arc-lang chat group:

We'll help you not feel silly when you ask legitimate questions as well as answer them.

I struggled to install it on my own too, but GPT 4 fixed that issue splendidly. I highly recommend you try: create a free account on if you haven't already (GPT 3.5 is free, GPT 4 costs $20/mo), and then give it a prompt similar to this:

"Help me understand how to install arc. When I try to install in racket it says:

racket: undefined; cannot reference an identifier before its definition >"

Here's how I used it for my own issues:

There was a pull request by samth that fixed this on the main branch, though I guess no one's ever ported it to the stable branch:

Just after that, Racket introduced an easier way to fix this, `unsafe-set-immutable-car!`, specifically as a stable way to mutate the so-called immutable cons cells going forward. :) We should probably move to that.

I've opened an issue for it:

Interesting. I haven't heard this one before.

The stable branch has this bug as well.

I'd compare how x-set-car! is implemented in the two versions. Current HEAD:


I suspect Racket's changed something in unsafe-set-mcar! during the move to Chez Scheme.

(Sorry I just saw this.)

1 point by zck 620 days ago | link | parent | on: Stuck on white page after installing news.

Odd. What is the page serving? It's never finishing loading anything? Does your browser's inspector tools show anything completing?

thanks for your reply, it's saying this:

    initializing arc.. (may take a minute)
    serving from C:\Users\user\anarki\apps\news
    starting app news
    load items:
    ranking stories.
    ready to serve port 8080

    To quit:
      arc> (quit)
      (or press ctrl and 'd' at once)
    For help on say 'string':
      arc> (help string)
    For a list of differences with arc 3.2:
      arc> (incompatibilities)
    To run all automatic tests:
      $ ./
      arc> (load "tests.arc")

    If you have questions or get stuck, come to
    Arc 3.2 documentation:
1 point by zck 630 days ago | link | parent | on: Stuck on white page after installing news.

Does the console where you've started up the news have anything printed out? You might also add some prn statements to figure out where you get.

Thanks for such a thorough answer. Lots to learn.

I made an attempt at this once in Anarki, but I wasn't really satisfied with the result. The anarki package has a `#lang anarki` language, with a demo in the /lib/racket-lang-demo directory.

Living link:

Pinned link:

In particular, this is /lib/racket-lang-demo/lang-anarki-library.arc, which shows what it would look like to use Racket libraries and other Arc libraries from a `#lang anarki`-based library:

  #lang anarki
  (:provide anarki-library-export)
  (= racket-deep-dependency-export
    ($:dynamic-require "racket-deep-dependency.rkt"
  ($:dynamic-require "lang-anarki-deep-dependency.rkt" #f)
  (load "plain-anarki-deep-dependency.arc")
  (= anarki-library-export
    (+ "from " racket-deep-dependency-export ", "
       lang-anarki-deep-dependency-export ", and "
       plain-anarki-deep-dependency-export "!"))

The `(:provide ...)` syntax is a special extension to the Arc language for the purposes of `#lang anarki`. Every `#lang anarki` file must start with `(:provide var1 var2 var3 ...)` fo r some number of variables (even zero). It describes what exports are visible to other Racket libraries.

I believe `#lang anarki` does something to make it so `(load "plain-anarki-deep-dependency.arc")` loads the file path relative to the directory the module is in.

There are a number of awkward things about using Arc to write libraries for Racket consumption:

- Racket languages typically have a notion of phase separation where some amount of the program (the compile-time part, i.e., phases 1 and up) happens during the process of compiling a module into a .zo file, and the rest of the behavior (the run-time part, i.e., phase 0) can be performed by loading the already-compiled .zo file. Arc programs are more like `#lang racket/load` in that they only begin macroexpanding the later expressions in the file after they've run the run-time parts of the previous expressions, so it's like the whole macroexpansion process has to wait until run time. The only things `#lang anarki` does at compile time are reading the file's s-expressions and processing the `(:provide ...)` directive.

- Racket and Arc both have macro systems. They both involve writing macro definitions in source-to-source styles that usually make it easy to write a macro that abstracts over another macro call. Sometimes, in more advanced cases, these styles require more attention to get the hygiene right. However, they use different "source" types (Racket's syntax objects vs Arc's plain s-expressions), and they have rather different approaches to hygiene (Racket's lexical information carrying module imports and sets of scopes, vs Arc's gensyms and global variable redefinition warnings). This means mixing Racket macros with Arc macros is one of the advanced cases; I expect that to get the interactions right, it may be necessary to do some explicit conversions between "source" types, as well as being proficient in both languages' approaches to hygiene.

- As far as a module system goes, Arc traditionally has no way to allow multiple pieces of code to see different bindings of the same top-level variable name. (Framewarc and I believe Arc/Nu have approaches to this, but they involve writing all macros differently than before.) Hence, two Arc libraries might fail to be usable together due to mutual clobbering of the same variable, which isn't a typical situation with Racket modules. If and when modular techniques catch on for Arc, those techniques may still be challenging to reconcile with Racket's techniques, so a `#lang anarki`-based library may still not present a very familiar interface to other Racket ecosystem programmers.

- Arc is a lisp-N with its various namespaces, like `setforms`, `defcall`, and `coerce`, stored as entries in global hash tables. Racket is a lisp-N with its various namespaces, like `set!` transformers and `match` expanders, stored on the same compile-time object by implementing multiple interfaces (structure type properties/generic interfaces). This is one particular place where reconciling the modularity approaches may be difficult.

- Racket's compiler tooling tries to determine statically what files a file depends on, both so that `raco make` and `raco setup` can recompile the file if its dependencies have changed and so that if a file is bundled up with `raco distribute` or `raco exe`, its dependencies are included in the bundle. This is something I didn't tackle at all with `#lang anarki`. Things like `load` and `dynamic-require` make it difficult to keep track of dependencies statically this way.

The design I chose for `#lang anarki` was basically to get something tolerable working with as little effort as possible. There's probably a lot of room for improvement, so I didn't consider it stable enough to show off in the `anarki` Racket package documentation.

I think a somewhat better approach would involve:

- Giving Anarki a read-time namespace system like Common Lisp's, to solve Arc's inadvertent name clobbering issues (while potentially still permitting intentional clobbering).

- Going ahead and macroexpanding a whole `#lang anarki` file at compile time, evaluating nothing but the `mac` definitions at first, even though that's not the usual Arc `load` semantics. User-defined macros can sometimes be slow, making it worthwhile to expand them before producing the .zo. Only so much Arc code actually cares about running certain expressions before others are expanded, and those cases can use a CL-style `eval-when` approach.

- Assembling static information about the module just by using `eval-when` compile-time mutable definitions. Then we could dispense with `(:provide ...)` and just have a global mutable table that collects all the exports of the current module.

One way to investigate this would be to use Racket's profiler:

That tool's results are a little tricky to navigate, but there's a kind of indirect way to turn them into flamegraph SVG images via this library and

Racket also has some support for getting feature-specific profiling data for certain features, although I haven't tried it for anything yet:

I think Arc's load time is pretty typical of uncompiled Racket code. In Racket, people can speed up their development process by using `raco setup --pkgs my-package` to compile their libraries or `raco make filename.rkt` to compile individual files. That might be harder to do for Arc, especially the Arc REPL, since Arc's macroexpansion is interleaved with run-time side effects.

I'm not sure how to answer that. If you're asking what the easiest way would be to speed up initialization, it would be to load fewer libraries. Since it's an anarchic fork, we've all added lots of ideas that are good in principle but not always needed.



I got it to work! I believe akkartik was right. Using command (-c) did the trick, which I assume ensured disconnecting from the database.

  (system "psql -U root -d root -c 'SELECT * FROM items'")

  item_id | name | type | description | created | location ---------+--------+------+-------------------------------------+----------------------------+---------------------------------------------------- 1 | marble | tool | A small, translucent orange bauble. | 2022-02-23 17:59:45.480545 | 0101000020E610000012C2A38D239A5EC040683D7C99E44240 (1 row)

btw, would this be the correct syntax for table-exists?

  (= dbconn (postgresql-connect "root" "root" password))
  (table-exists? dbconn "items")

>btw I caught a misspelled 'password' in postgresql-secure-connect:

oops. It's fixed, thanks.

Killing me. I don't think it's nginx..

Maybe it isn't disconnecting?

  (tostring (system "psql -V"))

  psql (PostgreSQL) 12.9 (Ubuntu 12.9-0ubuntu0.20.04.1)
just fine from the app.

Thanks! So far no avail, but I'll try some more!

btw I caught a misspelled 'password' in postgresql-secure-connect:

  (mac postgresql-secure-connect (user db ssl-protocol (o passowrd nil))

Hey Kartik!

It's a new project. However, Hubski has been using postgres for a few years, but it's currently an amalgam of Arc and Racket. I didn't write the db code, and am trying to start fresh. The Hubski racket connection looks like:

  (define db-conn
    (lambda () (postgresql-connect
           #:user db-user
           #:password db-pass
           #:database db-database
           #:server db-server

  (define db-user     "user")
  (define db-pass     "password")
  (define db-database "hubski")
  (define db-server   "localhost")
>Can you show what command you're running to check that you "can connect to the db from the Arc command line"?

Here's my test code that works in the command line, and the response. (I named my db "root" atm and will change that and the user once I get it working. I'm running the app as root.):

  arc> (tostring (pipe-to (system "psql -U root -d root") (prn "SELECT * FROM items WHERE name = 'marble';"))                                     )
  " item_id |  name  | type |             description             |          created           |                                                           
  location                      \n---------+--------+------+-------------------------------------+--                                     ------------ 
  --------------+----------------------------------------------------\n       1 | marble | tool | A small, translucent orange bauble. | 2022-02-23 
  17:59:45.480545 | 0101000020E610000012C2A38D239A5EC040683D7C99E44240\n(1 row)\n\n"
But when I have that same code in the app, it times out. I tried to add (prn "\\q") at the end, but same result. Works in command line but hangs up in the app.

I even tried to specify the host and port:

  (pipe-to (system "psql -U root -h -p 5432 -d root") (prn "SELECT * FROM items WHERE name = 'marble';"))
With this in my pg_hba.conf

  host    all             root        trust
And the same result; returns in command, app times out. Checked the port:

  root@Xyrth:/home/xapp# netstat -tulnp | grep 5432
  tcp        0      0*               LISTEN      124232/postgres
Thanks for the quick reply!

BTW, I am using the domain with a nginx reverse proxy. I just had the thought it may be my nginx configuration. It probably needs to listen explicity on 5432? Here's my current sites-enabled:

  server {
    listen 80;
    return 301$request_uri;

  server {
    	listen              443 ssl;
        ssl_certificate "/etc/letsencrypt/live/";
        ssl_certificate_key "/etc/letsencrypt/live/";
        ssl_session_cache shared:SSL:5m;
        ssl_session_timeout  10m;

        proxy_redirect      off;
        proxy_set_header    X-Real-IP $remote_addr;
        proxy_set_header    X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header    Host $http_host;

        location / {
                proxy_buffers 16 4k;
                proxy_buffer_size 2k;
		proxy_set_header Host;

        location ~* \.(png|jpg|tif|ico|ttf|woff|svg|eot|otf|mp3|ogg|wav)$ {
        root /home/xapp/static;
        expires max;

        location ~ ^/(xyrth.css) {
                root /home/xapp/static;
                expires max;


Hi Mark!

Is this on Have y'all been using postgres there for a long time? Or are you trying it for the first time?

Can you show what command you're running to check that you "can connect to the db from the Arc command line"? I wonder if the app is able to connect but not disconnecting for some reason. That would explain the "thread took too long" timeout message.

If you've written some custom code to connect to postgres, that'd be helpful to look at as well.

There is a database wrapper (database.arc) in /lib that should support postgres.

It isn't well documented and only tested on a SQL connection but it's just a set of wrappers around Racket's DB drivers, so you could try including that into your app.

Unfortunately I seem to have completely lost my test project but the connection should work as follows:

    (= dbconn (postgresql-connect user db password))
Hope that helps.
2 points by shader 778 days ago | link | parent | on: Bel in Clojure

That was a fun and insightful take on the experience of implementing Bel.

The 'lit concept is pretty nice; like tags, but more thoroughly integrated.

I also like the idea of integrating interpreter features more completely, with globe, scope, err, etc.

It raises a question though; how does Bel relate to the Arc community? Is it the full successor? Can they coexist somehow?

3 points by rocketnia 792 days ago | link | parent | on: Latest source?

Yes, it's the fork that's been maintained by the people here at Arc Forum. :) I recommend it.

Whether you want the community additions or not, you might also be interested in the "official" and "stable" branches of that repo. The "official" branch tracks the official .tar releases that you'd find on the front page here, and the "stable" branch tracks the official releases plus a few small bug fixes and quality-of-life improvements.

3 points by capableweb 792 days ago | link | parent | on: Latest source?

Read around a bit and found a community maintained fork which seems to be a bit more updated (, is that what people tend to use?

Tonight I did the same thing for the last of my Arc repos, Penknife.

  $ npm install --global rainbow-js-arc framewarc penknife-lang
  $ rainbow-js-arc init-arc my-arc-host-dir/
  $ framewarc copy-into my-arc-host-dir/lib/framewarc/
  $ penknife-lang copy-into my-arc-host-dir/lib/penknife/
  $ cd my-arc-host-dir/
  $ rainbow-js-arc run-compat -e \
      '(= fwarc-dir* "lib/framewarc/")' \
      '(load:+ fwarc-dir* "loadfirst.arc")' \
      '(= penknife-dir* "lib/penknife/")' \
      '(load:+ penknife-dir* "penknife.arc")' \
      '(pkrepl)' \
  pk> [+ arc["Hello, "] arc["world!"]]
  "Hello, world!"
Penknife really was just a pile of code before now. I originally wrote it on my commute using an Android phone. Now I've finally gotten around to giving it a readme, a .gitignore, and all that. Whew. :)

There was another language I called Penknife a couple of years later because I thought of it as having the same set of design goals, so technically this one's more like Penknife Mk. I. That's what I think I'll call it.

Something about Penknife Mk. I that I often think back to is its approach to macro hygiene.

Its syntax is primarily string-based, but with the ability for other values to be embedded inside the strings. It has a kind of quasiquotaton that surrounds the quoted section with an object wrapper that the macroexpander recognizes. When the macroexpander expands that expression, it switches over to using the scope at the macro's definition site. Interpolations in the quasiquotation are surrounded with another wrapper that causes the macroexpander to switch back to the caller's scope.

When the macro is defined, its lexical scope is captured and carried on the macro's binding. That way, it's the namespace that holds other namespaces inside it. The syntax trees don't have to hold namespaces; they can just hold paths to traverse the namespace hierarchy.

I still think of this as a nice sweet spot; the code has a context-independent enough identity to be compiled, while the namespaces are mutable enough to allow REPL interaction.

Racket's sets-of-scopes approach to hygiene is mature and supports advanced features like local macros and local definition blocks, but I think of it as kind of sloppy. It spray paints one piece of information over the whole syntax tree just to mark that a variable is in scope. This approach could be handy in cases where variable scopes overlap with each other in non-hierarchical ways -- where sometimes one variable is in scope, sometimes the other, and sometimes both -- but I feel like Penknife's wrapper objects are a much tidier model of the typical hierarchical structure. There've been many moments in my Racket programming when I would have liked Racket to have Penknife Mk. I's approach to hygiene instead.

- Penknife Mk. I on GitHub:

- Penknife Mk. I on GitHub (current snapshot link):

- Penknife Mk. I on npm (currently version 0.1.0):

- The Era repo on GitHub, home of Penknife Mk. II and a few other things:

- The Era repo (current snapshot link):


- Rainbow.js on GitHub:

- Rainbow.js on GitHub (current snapshot link):

- Rainbow.js on npm (currently version 0.2.1):

- Framewarc on GitHub:

- Framewarc on GitHub (current snapshot link):

- Framewarc on npm (currently version 0.1.2):

- The original Lathe repo (old link):

- The original Lathe repo (new link):

- The original Lathe repo (current snapshot link):

Another repo that I just forked off of the original Lathe repo is Lathe Comforts for JS:

- Lathe Comforts for JS:

- Lathe Comforts for JS (current snapshot link):

Yes it does.

    $ git clone
    # install Racket 7.7
    # create x.arc
    $ cat x.arc
    (prn "hi")
    $ anarki/
    arc> (load "x.arc")
But like I hinted, anarki is the community-managed fork and has 3 incompatibilities with Arc 3.2. Be especially careful if you're already managing a HN-like site using Arc 3.2.