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1 point by sacado 6508 days ago | link | parent | on: Nitpick: Why "rem" and not "rm"?

I don't like rem either. BASIC was my first language, and now, everywhere I see rem, at first sight I think it's a comment. I'd like rm much more.

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5 points by sacado 6509 days ago | link | parent | on: How Arc should handle vectors

vincenz is right : Lua deals with vectors this way. Actually, it doesn't even bother to ask you whether you are using it as a vector or as a hash table. Each table is implemented as both a vector (for numeric keys) and a regular hash table (for other keys).

This way, you've got performance (and lua is one of the fastest "scripting" languages) with a really minimal language.

I think that would be a good approach for Arc too : don't bother with vectors, hash tables are enough :)

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2 points by sacado 6509 days ago | link | parent | on: Arc Ported to JavaScript

I wanted to do the same thing in Lua, but I finally thought it was too much work... Since it can be done with Javascript, I guess I'll finally give it a try... You know, just to understand better how it does work...

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Very good app. This (and its source code) is the kind of things that makes me sure Arc is really a great language for webapps... How long did it take you to make it ?

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6 points by mattjones 6510 days ago | link

Seconded. Reading the source code is a lot of fun. It's well organized and really makes the case for Arc's approach to HTML. I know I'm a convert; having stuff in so many separate files, MVC style, feels like sludge compared to this. Even if you do have to start breaking things into separate files as the app gets more complex, being able to start out like this is a serious gain.

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3 points by brett 6509 days ago | link

Thanks. I'm not sure exactly how long. There was a lot general arc exploration mixed in with hacking on the app.

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1 point by sacado 6510 days ago | link | parent | on: Fix: UFT-8 in app server

Yep, it's working ! Thanks !

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5 points by sacado 6511 days ago | link | parent | on: Poll: What would you change in Arc?

I think the most wanted feature is Unicode.

This is a big one but a simple solution is possible in a first time. Since Arc is mainly for web apps, why not at least convert non-ascii characters into their url-encoding equivalents ? Arc is already converting those characters, but in a broken way : EUR instead of the euro symbol, for exemple.

Modules would be great, too. Well, nothing new here, anyway.

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5 points by sacado 6511 days ago | link | parent | on: Bug in hash tables ?

Thanks for your answer Paul ! However I think I'm still missing something because display seems to work fine :

buggy ==> #0=#hash((#0# . t) (buggy . t))

(ok, we can see it is circular here, but no infinite loop)

However,

(if (buggy 'buggy) 'yes) ==> yes ; ok...

(if (buggy buggy) 'yes) ==> infinite loop...

Here, no display of the table seems to be involved ?

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5 points by pg 6511 days ago | link

Oops, that does look like a bug. Will investigate. Sorry for not actually testing it before.

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4 points by nex3 6511 days ago | link

It looks like an issue with Scheme, rather than Arc. Check out the following Scheme session:

  > (define t (make-hash-table 'equal))
  > (hash-table-put! t t 'foo)
  > t
  #0=#hash((#0# . foo))
  > (hash-table-get t t)
  ; Loops forever

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3 points by soegaard 6511 days ago | link

"Issue". It behaves as specified. From R5RS:

Equal? recursively compares the contents of pairs, vectors, and strings, applying eqv? on other objects such as numbers and symbols. A rule of thumb is that objects are generally equal? if they print the same. Equal? may fail to terminate if its arguments are circular data structures.

There is a silver lining though. In R6RS the following was added:

  Note: The equal? procedure must always terminate, even if its arguments contain cycles.
That is, there is a good chance that the behaviour of equal? changes, when the PLT Scheme team begins implementing the R6RS language.

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1 point by sacado 6511 days ago | link

I submitted a bug report to PLT Scheme about that. Here's their answer :

"The process for generating an `equal?' hash key is defined to not terminate on circular objects, such as a hash table that contains itself. So `(hash-table-get <any-table> t)' loops trying to generate a key for `t'.

The specification of hashing has changed for the next release to deal gracefully with cyclic data, just as `equal?' has changed so that it can compare cyclic data. In the current pre-release version, v3.99.0.10, your example returns immediately.

(It returns with a "key not found" error. That's because the process of installing a hash table into itself changes the table's own `equal?' hash key.)"

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