It opens the door another issue though: If you end up making two instances of a language core or a library, what if you want a value from one to mean the same thing in the other, but that value's meaning depends on something each module generates for itself, like a gensym or a mutable data structure?

For example, my lang hack (http://awwx.ws/lang2, also in Anarki) lets you call Python libraries from Arc, and as it happens I've heard that it has been used in production (http://news.ycombinator.com/item?id=1814558). If my lang hack does what you need you can use it, or if there's something missing that you would need you can tell me what's missing for you and maybe I can help.

"I call Python from Arc when there's a Python library that would be useful to me."

Yup, I agree with both of those. Python is ew compared to Arc, but it does have some nice libraries.

Incidentally, I started on Arubic for fun, to learn more about how an Arc interpreter works, and also to enable nice integration with Python. Then I can finally use multi-expression lambdas with Python. :P

Oh yeah, and change some stuff that I felt Arc was lacking in.

Plus, I like Python better than Racket. So if I'm going to hack in one of the two...

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"http://awwx.ws/lang2 "

I think d0m's saying: Why do Arc folks do things like X by making a new language? Shouldn't we put features in Arc itself, if it's going to be a language people will actually use?

I think aw's saying: Why not ask instead, "How can I do X in Arc?" In fact, here's a way I do X without making a new language.

I think Pauan's saying: I'd like to do X, and aw's approach seems clunky. I think a new language would be better.

---

As I see things, d0m, we pursue our own languages because there are certain improvements we want to make that take a complete rework of the language.

Python interop is a great example. Clojure-Java interop is possible because they both run on the same rather high-level platform, the JVM. Official Arc runs on the Racket runtime, and Python (at least CPython) is its own whole runtime, so there aren't many ways to bridge the gap except for the C FFIs and the kind of IPC aw's lang hack uses. One of the best ways to get a clean integration between Python and Arc would be to reimplement Arc and/or Python to run on the same high-level platform--and yet that means reimplementing a language, rather than improving an existing one.

Or does it? The reimplementations may already exist. If you could use Jython for your Python project, then you could probably achieve a good degree of interoperability with Jarc and Rainbow, which are high-quality Arc implementations for the JVM.

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But really I think Python interop was only one example, and your point was any that features we could put into the main Arc language should be put there. In that case, you'll need to define what counts as Arc.

There's an official release of Arc, maintained by Paul Graham, but keep in mind that he only updates once in a blue moon and tends to leave out features that aren't obviously necessary to him. A brief language implementation is one of his primary goals for Arc.

We do have Anarki, a community fork of Arc, but keep in mind that Anarki is held back a little by a desire to be similar to official Arc, so that the next time Paul Graham releases an update, it's easy to merge it in. This similarity also makes Anarki a bit more useful in practice, since it's compatible with most official-Arc code people write.

We could probably relax that policy on Anarki, but what big changes should we allow? I'd make radical changes and turn it into Penknife. Pauan would make sorta big changes and turn it into Arubic. It could be useful to make radical implementation changes and turn it into aw's ar, and akkartik may want to radically reorganize the project's file tree.

All in all, Arc's philosophy isn't well-defined and persuasive enough to drive us all toward the same future. Although we do want to make big changes, it's easy for us to be unsure about them or disagree. So we tend to experiment with big ideas by implementing them in our own language projects, where at least we know what we like.

If it helps, think of it this way: We don't make our own languages just to let Arc stagnate. We make our own languages so that we can improve Arc in various ways all at once. This fracturing is kind of unfortunate, but we still do build upon each other's ideas, so we're just advancing the state of the Arc in an unusual way. ^_^

With respect to there being lots of variants of Arc, I think about Arc as a personal programming language. Thus that it allows extensive personalization, and people publish many personal variants, is to my mind a feature not a bug.

This diversity of course raises its own issues: we're concerned not just with interoperability between Arc and other languages, but interoperability between variants of Arc! :-) But solving this provides a more powerful platform than one stuck with providing the lowest common denominator of standard language features to ensure interoperability.

I've never thought of that. I'm used to using Racket stuff from Arc without hesitation, but then the stuff I use is provided with the Racket language, like parameters and regexes. Most of my non-Arc personal code is in Java or Groovy, and I'm very glad I can use it from Rainbow, but I haven't actually done that yet....

With arc, the language syntax and base libraries are awesome, but you scratch your head more often, wondering" well how the hell am I supposed to do that. " And these problems/features are not small roadblocks... For example, if I need to use Arc connecting to oracle? - good luck, it's not going to happen.

Thanks for the offer. I think real database connections to arc could only improve the adoption + user happiness levels, but I will suggest connecting to oracle was just an example for the point I was trying to make.

What I am suggesting is not new or even surprising. Arc has no depth for libraries. Rich solved this problem right from the get-go by having tight integration with java. Arc would have had similar success had it done the same thing - too bad really. And dropping into Scheme just doesn't cut it.

I'm suggesting users of arc will google things like 'arc oracle', or even 'scheme oracle' which returns jack. With Arc you get Nada for google answers + you get unanswered posts such as these.

http://arclanguage.org/item?id=10839

However google 'clojure oracle':

http://en.wikibooks.org/wiki/Clojure_Programming/Examples/JD....

step-by-step recipes to connect to a myriad of databases. This was made possible through Clojures tight integration with java. Clojure can import java libraries with 1 simple import statement.

Let's not forget that Clojure is a newer language than Arc - correct?

Now, I'm just looking at the title of the thread "Effort to make it easy to use in production?", and thinking - yeah, I can understand, that's why I moved over to Clojure and its too bad Arc didn't do this.

Sure I'm no expert in the programming language industry, but if I were to come up with a new spiffy language I'd rather do what Rich did. Arc could have been built atop the jvm - correct? It was just easier not to, considering arc was not about being practical, it was about attaining some elusive mystical idealized syntax that will be practical in, possibly, a hundred years from now.

The JVM naturally has the advantage that it's easy to call Java libraries, but it has the disadvantage that it has no built-in support for tail call optimization or continuations. Since it's not particularly difficult to make use of libraries running in a different process, it would be easy enough for me to use Java libraries from an Arc implemented in Racket if I wanted to, and so I had no compelling reason to write ar on top of the JVM.

There is a long history of languages written for people who want to use the JVM but who also want to be able to use a less terrible language than Java: Jython, Groovy, Clojure, etc. Since Clojure is a particularly nice language, it didn't surprise me that it rapidly gained popularity among people who want to use the JVM.

For any particular project that I may be working on, there are a mix of features that I need for that project. If I were working on a project that primarily needed to call Java libraries and I didn't need the features unique to Arc, I would most likely use Clojure myself (or Rainbow or Jarc, if it turned out that one of those were suitable to my project). If I were working on a project where the features of Arc were important and I also needed to call some Java libraries, I'd likely write it in Arc calling out to Java libraries.

Since this is a forum for Arc, I answer questions primarily from the perspective of Arc. Since typically a hundred people will browse a forum for each person posting, I primarily answer questions for the majority reading. For example, if someone makes a statement that is wrong, I will say that they are wrong, so that someone else reading the forum isn't left with incorrect facts.

When someone complains about Arc, I tend to suspect that either there's something they want, or else they just feel like complaining. People wanting things is useful. If someone actually wants X and says so, and we come up with a solution for them, then we also help the hundred other people who want that thing as well. Other the other hand, and I'm not saying that anyone has actually done this, but if someone were to sit at a computer and type in a complaint that other people haven't done the work to make Arc a popular language faster than some other language has become popular, that doesn't strike me as being particularly useful.

I'm not against complaining. Complaining is often a useful first step towards finding a solution. However, while I'm not trying to pass judgement, I am trying to discern whether someone is complaining because they just want to complain or because they want a solution.

Sure, if you have spent hundreds of hours doing low level hacking between racket<->arc you can suggest these things are not all that hard, but the reality is that many of these feature-x's are just not going to happen.

Chances are that mainstream features are not a priority for the members here... And that's my message to the OP: go use Clojure or something having the features you want. I say this from 2 years of following arc, the arc forum and its members. There are probably a dozen submissions/comments about db connects and FFI, yet to this day nothing works.

> "If you like the Arc, then instead of complaining that other people aren't figuring out what you'd want to use for you, why not take the time to help and describe what you would need in a db connection library and FFI?"

I'm thinking if you re-read the thread starting from my first comment (http://arclanguage.org/item?id=14539), you'll hopefully come to understand that I haven't been complaining, but rather I have been defending/substantiating my suggestions and thoughts.

As for why I don't take time to describe some spec, well because I'm not asking for anything and I've chosen to spend the bulk of my time learning Clojure and building applications. I guess you could say I take my own advice.

> "If you want some love on the forum, there's an easy way to get that:make a useful contribution."

Or, you could add a page to the wiki describing the ways that Clojure is better than Arc.

Since then, Jarc's actually added Rainbow compatibility functions, so you might be able to get away with writing code just for Rainbow without leaving Jarc too far behind. Rainbow's faster, but Jarc has a more straightforward implementation.

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I didn't plan to hack on programming languages when I started playing with arc. Creating new languages/implementations is an occupational hazard of hacking on arc. Or maybe it's a pleasant side effect that we get for free (a viral - and rapidly mutating - language). Depends on how you look at it.

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a) Can one use Arc to call Python and call Python from Arc? Yes.

b) Could you, if you wanted to, learn how this is done and package it up in a way so that it would easy to use? Sure, you could do that, if that was a way that you'd like to contribute.

First, some definitions:

  (def fn-latemac (mac-getter)
    (annotate 'mac
      (fn args `(,(mac-getter) ,@args))))
  
  ; Not to be hypocritical, let's implement 'latemac as if by using
  ; 'latemac.
  (mac latemac (globalvar)
    `(,(fn-latemac:fn () fn-latemac) (fn () ,globalvar)))

  (mac foo ()
    `(,latemac.do
       (,latemac.prn "this is macro foo expanding into bar")
       (,latemac.bar)))
  
  ; Oops, now let's define 'bar. Go go, late binding!
  (mac bar ()
    `(,latemac.prn "yo, this is macro bar"))

(For future reference, I'm using https://github.com/awwx/ar/commit/c375d77bd2dbf6ca8850fda5f6.... )

  arc> (foo)
  this is macro foo expanding into bar
  yo, this is macro bar
  "yo, this is macro bar"
  arc>
    (def bar ()
      (prn "hi, this is bar"))
  *** redefining bar
  #<procedure:g1590>
  arc> (foo)
  this is macro foo expanding into bar
  hi, this is bar
  "hi, this is bar"

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"[...] ideally ar would be powerful enough that someone could implement e.g. keyword arguments as a library."

Would be awesome if we could figure out a way to do that.

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""I could implement keyword arguments if only ar had X" is more likely to win me over to thinking about the best way to add X to ar."

I'll give some thought about the precise requirements for keyword args. Message passing too.

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"With respect to backwards compatibility... since ar is supposed to be hackable, one of the ways it should be hackable is to get it to produce a runtime that is mostly compatible with Arc 3.1. But on the other hand, if someone wants to implement a language which is completely incompatible with Arc 3.1, they should be able to do that as well."

Would be awesome if we could figure out a way to do that.

I'm guessing that a module system in the spirit of Arc would correspond more to Racket namespaces. Maybe I ought to be able to say something like:

  (module arc
    (load "foo.arc")
    (bar))

  (mac module (name . body)
    `(let ,name (new-namespace)
       (eval '(do ,@body) ,name)
       ,name))

  (w/namespace (new-namespace)
    (load "foo.arc")
    (bar))

  (import foo "foo.arc"
          bar "bar.arc")

  (w/namespace foo
    ...)

  (w/namespace bar
    (load ...)
    (load ...)
    ...)

  (w/namespace (current-namespace)
    ...)
  
  (w/namespace (current-environment)
    ...)

  (w/namespace (table)
    ...)

point can be used in the kind of situation that you might want to use Racket's raise for. In fact, you can think of point as a macro that creates a "raise" function.

Python doesn't have continuations, so the only way to break out of multiple layers of function calls at once is by catching and throwing an exception.

There are situations where something happens in a program that we expect to happen (at least sometimes), and we need to stop doing what we're currently doing and start doing something else, and often pass some data along that we need.

However, I noticed in production code written in Python where throwing and catching an exception is used to implement this, it's not uncommon for the implementation to also catch other exceptions that the programmer didn't expect... leading to real errors arising from bugs not being reported.

So I think for this scenario at least, using point/catch/throw is a better mechanism because it's explicitly only catching the things you plan to throw, and thus leaves handling unexpected conditions (things you didn't plan for, and so are actual bugs in your program) to the error handling mechanism, where you want debugging information like the source code line location and so on.

However, that does raise one question: should we have exceptions at all?

Note: I do actually want to use `err` in my program, because I want all execution to halt. I just want it to halt after all the errors are finished, rather than after only one error.

Yes. quit exits the process, and the operating system closes all open files when the process terminates.

However, that does raise one question: should we have exceptions at all?

Do we need the colons? That is, if we leave them off, is there anything that doesn't work?

Association lists could be (x 1 y 2) instead of ((x 1) (y 2)), and ('(x 1 y 2) 'y) could be implemented to return 2.

Yes! It's necessary to distinguish between keyword args and normal args:

  (foo x y :a 3 :b 4)

In any case, you can freely mix alists, plists, plists with keyword symbols, and ordinary tables in your own code. The question of this post is: should keyword plists be supported at all?

By the way, one benefit of alists is that you can iterate over them easier:

  (each '(k v) '((a 1) (b 2) (c 3))
    ...)

  (each '(k v) (pair '(a 1 b 2 c 3))
    ...)

  (each :(k v) '(:a 1 :b 2 :c 3)
    ...)

  ; or this...?

  (each (:k v) '(:a 1 :b 2 :c 3)
    ...)

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* [1]: http://www.gigamonkeys.com/book/practical-a-simple-database....

http://www.ida.liu.se/imported/cltl/clm/node108.html

http://www.augustana.ab.ca/~mohrj/courses/common/csc370/lect...

  ('(x 1 y 2) 'y)    -> 2
  ('(:x 1 :y 2) 'y)  -> 2
  ('(:x 1 :y 2) ':y) -> 2

  ('((a b) 1 (c d) 2) '(c d)) -> 2

So in this way your idea and my idea would work out the same: both would pass the string "foo" to the handler when (err "foo") was used.

A difference would be primitive errors generated by Racket, with my approach the handler would get the string like "/: division by zero" while with your implementation the handler would still get the exception object.

I don't think we'd want it to matter if errors are generated internally by Arc or Racket, so assuming that we do want to continue to raise errors in Arc with (err "foo") then I'm guessing we'd want to special case Racket exceptions and pass the exn-message string to the handler so that it would end up working the same way.

That actually makes me wonder if Arc should have access to 'raise as a separate function from 'err. After all, if we catch a Racket exception as a string, we lose information.

For all I know, losing that information isn't so bad. I almost always design code so it never throws exceptions that should be caught, so I don't know what information is useful to have in an exception. I've only encountered two places it makes sense to capture an exception:

- When the exception implements an escape continuation, in which case the necessary information is the unique identity of the catch point.

- When the program is something like a REPL or server that handles multiple commands and should typically recover from an error encountered in any one command. In this case, the necessary information is whether the error should be considered severe enough to take down or restart the particular command loop in progress. The usual approach to representing this information is a hierarchy of types such that, if you say exn:fail is okay, you implicitly say exn:fail:contract:divide-by-zero is okay. Is there a better approach?

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By the way I don't think you do want to use call-with-exception-handler; if the handler returns[...]

That handler doesn't return, but good point.

Reading over the reference some more (http://docs.racket-lang.org/reference/exns.html), it looks like there are some potential things to consider with breaks:

"...the exn:break exception typically should not be caught..."

"Before any predicate or handler procedure is invoked, the continuation of the entire with-handlers expression is restored, but also parameterize-breaked to disable breaks."