Anarki – Community-managed fork of the Arc dialect of Lisp

126 44 8 years ago

What are the core features that differentiate Arc from other lisp dialects?

sctb5• 8 years ago

To me, one of the most fundamental features of Arc is taking the unification of code and data much further. I don't know of other Lisps that do this! K is another language that does.

  arc> (= l '(1 2 3))
  (1 2 3)
  arc> (= f [+ _ 1])
  #<fn: f>
  arc> (map l '(0 1 2))
  (1 2 3)
  arc> (map f '(0 1 2))
  (1 2 3)

prospero• 8 years ago

Clojure’s maps, sets, and vectors are all functions.

agumonkey• 8 years ago

This was discussed a lot before (according to Queinnec book at least) but people were worried that too much overloading would yield confusing code and bugs.

sago2• 8 years ago

I don't know Arc, so this confuses me:

  arc> (map l '(0 1 2))
  (1 2 3)

What is the logic here? Is l made into a function that holds state and returns each element in turn (like an iterator function)? Because I would've expected:

  arc> (map l '(0 1 2))
  ((1 2 3) (1 2 3) (1 2 3))

In what way is map being applied here?

jlarocco• 8 years ago

No offense, but I found your example code really confusing.

For the benefit of people familiar with Common Lisp:

  * (= ...) is assignment, not equality testing
  * (map list index-list) is equivalent to (loop for index in index-list collecting (nth index list)), or in a more FP style (mapcar (rcurry #'nth list) index-list)
  * (map function list) is equivalent to (mapcar function list)

I think your example would have been less confusing if it used larger numbers to highlight where addition was happening and where indexing was happening:

  arc> (= l '(4 5 6))
  (4 5 6)
  arc> (= f [+ _ 10])
  #<fn: f>
  arc> (map l '(2 1 0 0))
  (6 5 4 4)
  arc> (map f '(0 1 2))
  (10 11 12)

jessaustin• 8 years ago

Wow next time don't use

and

in the same code listing.

malloryerik• 8 years ago

Kind of like pattern matching in Elixir?

christianbryant2• 8 years ago

If you take a look at the code for HN written in Arc, you can compare it against other Lisp dialects. I point to this as it is possibly the most widely-used and familiar application to most here written in Arc.

https://github.com/wting/hackernews

This is a great place to start with understanding Arc, as the jump to Anarki (an Arc fork) will make more sense as it comes bundled with News - a Hacker News style app - which is fun to play with if you have experience with HN and want to try a variation of this site.

quadcore2• 8 years ago

It is more concise thanks to "sugar" in the language.

gtdthrow2• 8 years ago

Am I understanding right that Arc is a Lisp-1, like Clojure?

sctb5• 8 years ago

Yes, or like Scheme.

gtdthrow2• 8 years ago

I don't really get why you'd ever want a Lisp-2. Is there an argument/explanation somewhere that I could read up on?

(I've used Clojure and JS, which also seems like a "Lisp"-1 in that you can just put fns into variables and call them like 1st class fns, I just don't get why the distinction is in any way positive rather than confusing, and in Lisp-2s you now need to dereference everything all the time, like in Ruby).

dreamcompiler• 8 years ago

The curse of Common Lisp is that every good programmer who tries it wants to improve it. Which always results in a weird product with less, rather than more, appeal.

andreareina• 8 years ago

The intention is to be extremely permissive in accepting patches.

Interesting to see what this will lead to.

krapp• 8 years ago

I'm not nearly versed enough in either lisps or Arc to comment on it as a language, but as far as the architecture of the forum is concerned, what is the rationale for functions that appear to just print CSS and javascript[0]?

Wouldn't it be better to separate CSS and JS into separate, static files and only have the forum deal with, at best, IDs and classes in HTML?

I'm asking because I'm tempted to actually try to fork it and make a PR for it but it seems like such a simple and obvious bit of housekeeping that I have to assume there's a reason no one else has bothered yet.

[0]https://github.com/arclanguage/anarki/blob/master/lib/news.a...

Anarki – Community-managed fork of the Arc dialect of Lisp

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