Having spent a lot of time meditating on it (as sofuture mentioned), it isn't "slightly obfuscated" so much as "stubbornly written like APL rather than C".

If you become inexplicably fascinated by that code and want help unraveling it, my contact info is in my profile.

I don't consider it noteworthy as a useful program under 2kloc (on modern hardware it usually just crashes, it's quite cavalier with pointer casting, and clearly a quick prototype either way), but it's like a pink space laser beam of insight about the APL mindset. Real APLs take more than a page, but not that much more. Eliding loops does that.

A lot of the IOCCC code is also delightfully perverse, too. Highly recommended.

Yeah, I realized that fact a little late. Relevant snippet from the link about that initial bit of code for J:

I showed this fragment to others in the hope of interesting someone competent in both C and APL to take up the work, and soon recruited Roger Hui, who was attracted in part by the unusual style of C programming used by Arthur, a style that made heavy use of preprocessing facilities to permit writing further C in a distinctly APL style.

Arthur's C is stubbornly unconventional, but often, he's got a point.

Also, the APL community seems to be pretty disjoint from the rest of CS (though Arthur is also a Lisper). I think it'd be mutually beneficial if the APLers and the MLers got together, in particular.

"That's interesting, but damn is that some ugly code"

I would disagree. That code is beautiful. Elegance and brevity; it's as close to a pure expression of the coder's thoughts as it's reasonably possible to get.

Excuse me, but in my programming thought flow, there are checksums and limits, not c's and l's, and my code reflects that. Do I not qualify as a coder?

Quick, what does the i stand for in "for (i=0; i<n; i++) {"?

It was a quick prototype written by one APLer, for another APLer, using mutually understood conventions. For example, its dyadic verbs ("V2" functions) use the variable names 'a' and 'w'. For a while, I wondered why (maybe they stood for "Arthur" and "Whitney"?), but after reading Iverson's _A Programming Language_, I realized APL usually uses lowercase alpha (α) and omega (ω), which look like 'a' and 'w' in ASCII. Details like that would need no explanation.

Likewise, in

    typedef struct a{I t,r,d[3],p[2];}*A;

t is type (is it boxed? 0 or 1), r is rank (number of dimensions), d is the dimensions (hardcoded to a max of 3; a 2x3x4 matrix has d={2,3,4}), and p is a variable-length array sized by malloc-ing extra space; that's where the values go, either longs or void pointers). That'll save you some time if you ever try to pick the rest apart. :)

APL code is often terse to the point of seeming cryptic, just math papers are. You get used to it, and it's that way for a reason.

Wow, thanks for that clue. Will have to take a closer look at that source now. I don't feel too bad for not really getting it, given the creator of J saying this about it:

My immediate reaction on seeing the page was recoil and puzzlement: it looked nothing like any C code I had ever seen. (“Is it even C?”) However, Ken counselled that I should reserve judgment. As recounted in An Implementation of J, it then happened that:

I studied this interpreter for about a week for its organization and programming style; and on Sunday, August 27, 1989, at about four o’clock in the afternoon, wrote the first line of code that became the implementation described in this document.

The name “J” was chosen a few minutes later, when it became necessary to save the interpreter source file for the first time.

If it intrigues you, check out Henry Rich's _J for C Programmers_. There's a free PDF on Lulu, and it's included with J (http://www.jsoftware.com/).

Like Emacs, J's internal documentation is excellent, but you have to learn its idiosyncratic terminology before you can actually find things.

I obviously can't speak to Arthur Whitney's state of mind circa some summer afternoon 1990, but I don't believe the code is an attempt to obfuscate or be snobby/elitist at all. He was simply trying to express the basics of an idea in a terse form. It's the APL way.

I, for one, am happy simply finding the code 'of interest'. It's not great code, it's the initial sketch of an idea (I'll bet you AW would admit that readily (plus Roger Hui refers to it as "Incunabulum", which seems a bit tongue in cheek)) -- but, it's certainly not something you see every day, and it is thought provoking.

Nevermind the comment about it being slightly obfuscated. Have to realize that this is the creator of J we're talking about. He probably saw it as highly expressive code (much meaning in as few characters as possible). Though I can't agree, it is definitely amazing that something so small could be the start of something like J.

It was actually written by Arthur Whitney, the author of K (not J), though Roger Hui (of J) studied it beforehand.

I do recommend studying it, though. Their APL dialects are really something; I wish there were good fully open-source implementations, and writing one is on my queue. Kona (http://github.com/kevinlawler/kona), an open-source implementation of K 3.2, is also coming along.

Just be warned that APLer C is usually nasty, brutish, and short. :)

FWIW, the best thing I've seen for getting the J mindset is _J for C Programmers_ - as Henry Rich says, to do J you must "think big" - don't think "for each part of this list, do this, then this, then this...", think, "apply this operation over these.". That scales up to multiple dimensions, and can often be run in parallel. :)