There's a trick to it. I was reading Ken Iverson's Notation as a Tool of Thought paper (look it up, it's worth a read) which is basically a whistlestop introduction to APL. I realised that it's very difficult (for me) to reason about when I read it left to right, but it's almost trivial read right to left.

That's right, it's a language that makes more sense backwards than it does forwards.

I heard somebody describe APL as associating "left of right", rather than "left to right", and it suddenly made sense. Reading it right to left is like reading it from the inside outward.

People who know APL can read it. I've been dabbling in J and K off and on, and it makes sense to me, though I still need the dictionary. APL code looks dense and intimidating, sure, but so does a page of Chinese. Both use ideograms rather than words made of letters, but the APL vocabulary really isn't that large. You probably already know what + does.

Also, I can't read Bosnian, but that says more about me than Bosnian. It doesn't make it a "write-only language".

But Chinese isn't any more expressive, just shorter. The fact that you type "國" instead of "nation" is only lexicographically compact, not semantically. Studies show that proficient readers of Chinese do have marginally higher speed and comprehension than phonetic languages, but that doesn't translate into being more expressive.

At risk of being slighty Euro-centric, in fact, from what little I know, western literature and tradition seems to have more emphasis on semantic content and the conveyance of literal ideas than does most Chinese.

APL is also semantically compact, because every verb implicitly maps over a whole collection.* This interests me more than the whole "programming with wingings" bit, but that's the part people get hung up on. Like all those damn parentheses in Lisp, or the whitespace in Python. (Shrug.) I'm more interested in J, which limits itself to ASCII.

* Joy also does this, but seems much less practical.

Chinese is also not a great comparison, because the vocabulary is so large. I originally said Turkish, then Bosnian, but changed it to Chinese because the "page with a grid of Chinese characters" is probably how most people think APL looks.

> Also, I can't read Chinese, but that says more about me than Chinese. It doesn't make it a "write-only language".

On the other hand, the fact that the Chinese have put their language through several reforms because of systematic problems with literacy and reading comprehension does show that, on a continuum between "readable" and "write-only", the Chinese language leans more toward the latter.

True, but I think you're focusing on the wrong aspect. (I originally said Turkish, then Bosnian, then decided that the ideogram-rather-than-letters aspect was worth drawing a parallel to Chinese, and have since changed it back to Bosnian.)

The parallels to actual human languages also break down here - reading APL is intimidating like reading Chinese, but it also has less than a hundred symbols (fifty-ish, IIRC), so it's really not comparabl in terms of "systematic problems with literacy and reading comprehension". I think the APL-languages are more like vi. Do vi(m) users think "9kdd2jp"? In writing, it looks like noise.

I don't think that follows. The causes could be primarily historical, for example. One would have to have detailed knowledge to make a case here.

The reason people can't read APL easily is it's one of many languages programmers know. If APL was the ONLY programming language any ever used anywhere, then all programmers would be able to read it easily after a little programming experience. Natural languages have the tersest syntax around, and people understand them easily because it's the ONLY language they learn, or one of only a handful if they're polylingual. It would be the same with a programming language.

Not really... The syntax of natural languages isn't really comparable with programming languages. Completely different modes of understanding. Calling programming languages "languages" is only an analogy. Humans have highly evolved linguistic capabilities that don't really apply to programming languages (though if you could invent one that leveraged natural language capability, you might have something very interesting on your hands.)

Vorg is simply saying -- and is quite right -- that APL is regarded as unreadable only because it's unfamiliar. People who know APL-based languages are amazingly proficient with them. The "write-only" slur is a canard. (Actually, these languages constitute one of the truly great contributions to programming. APL belongs on a short list with Lisp, Smalltalk, C, Forth, and very few others.)

It's depressing how the computing world is overrun with majoritarian prejudice. Even here. I suppose it's just human nature, but an open mind is so rare.

I do hope I don't fall into that camp. I learned programming in BASIC, moved on to game development in C/C++ and DirectX, programmed professionally in Java for 6 years, learned Scheme, learned Clojure, wrote a book on Clojure, am now learning Haskell...

But I was motivated to do all of that because of people I respected who said "This contains some genuinely new ideas worth learning." So far, I haven't heard anyone say that about APL, and so I guess I assumed that either its differentiation was only in a hyper-terse syntax, or that it was not generally suitable for a generalized programming language (similar to regex).

If that's an invalid assumption, then please point me towards an article elucidating what's great about APL, and I'll read it sincerely.

APL contains some genuinely new ideas worth learning. I'd suggest looking into J, as a more accessible and modern APL dialect. (K / Q is also really, really cool, but J is less commercially restricted.)

I was just curious because it was so different, but the thing that really convinced me was going through some of the J "labs" (a bunch of math lessons included with J, that incidentally teach it along the way) and spending a couple hours picking apart this code (http://nsl.com/papers/origins.htm) to get into the APL frame of mind.

I would suggest not getting too hung up on the syntax, and instead focusing on the pros and cons of doing everything over collections by default, with implicit looping. "Thinking big", as Henry Rich calls it in _J for C Programmers_ (also a good resource). The ideogram-based syntax is an historical thing, and getting fixated on that is like thinking the only novel thing about Lisp is all the parens.

See also: "The World's Most Mind-Bending Language Has the Best Development Environment" (http://prog21.dadgum.com/48.html)

Oh, then I think you'd find a lot to like about APL/J/K. It's not just that they contain genuinely new ideas worth learning; they're mindblowing in the way that Lisp and Forth are. I agree with silentbicycle that your best bet is probably the tutorials that ship with J (http://www.jsoftware.com/start.htm). The closest thing to a manifesto is Iverson's Turing award lecture Notation as a Tool of Thought (http://www.jsoftware.com/papers/tot.htm). But the really hardcore, beyond mindblowing stuff is Arthur Whitney's work on K, Q, and kdb. (Edit: the Q book is available online at https://code.kx.com/trac/wiki/QforMortals2/contents, user and pwd "anonymous").

I second what gruseom says: K (and Q, the newer version of K) is amazing. J seems more theoretically satisfyingly mathy to me, but K is a straight-up hacking language. It's really too bad that it's closed and oh-so expensive (but since it was made for real-time stock trading, and it works, I'm not surprised).

Here's a good intro, by Arthur Whitney himself: http://www.vector.org.uk/archive/v101/whitney101_74.htm

Interesting. Downloading the non-commercial Q implementation and checking it out.

Hey, let us know if you find anything that piques your interest.

Just because you understand a language does not mean you understand or recognize all algorithms that can be expressed in that language.

Yeah, but that's hardly limited to APL.

That's why I said 'language' and not 'APL'.