alt.hn

4/11/2026 at 5:34:10 PM

The APL programming language source code (2012)

 https://computerhistory.org/blog/the-apl-programming-language-source-code/

by tosh

4/11/2026 at 11:05:49 PM

APL is how non-programmers imagine what programming is, a kind of sorcery involving exotic symbols and elaborate ritual processes to create data and algorithms out of thin air. Like LISP, it's an eternal classic that every generation rediscovers and gets their mind blown as an educational experience about the strange nature of computing, logic, and language.

Notation as a Tool for Thought, the 1979 ACM Turing Award Lecture by Ken Iverson who developed APL, is insightful in understanding some of the thinking behind it.

by lioeters

4/12/2026 at 8:56:15 AM

PDF of the lecture: https://www.eecg.utoronto.ca/~jzhu/csc326/readings/iverson.p...

I found this part remarkable:

> The executable language to be used is APL, a general-purpose language which originated in an attempt to provide clear and precise expression in writing and teaching, and which was implemented as a programming language only after several years of use and development.

This is also how Python started out! I always thought, "Python is so easy for beginners because it is a teaching language." Well, so is APL!

by andai

4/11/2026 at 11:41:34 PM

I went out to talk with a guy, back in about 1995, in Chicago, fired up APL on his notebook, loaded the JPMorgan Risk Metrics data set, fiddled a bit, and reduced the thing to a one-line formula in an interactive window - like a Jupyter Notebook.

by flint

4/11/2026 at 11:49:57 PM

APL was the first programming language I learned, I was obsessed with learning every intricacy of the language. I almost lost my mind when I had to switch to a procedural language. APL warped my mind in such a way that it took almost a month to feel comfortable using anything else.

by QuantumSeed

4/12/2026 at 6:09:30 AM

Wow! I never thought of this perspective. For most people, procedural is the first concept. If they ever start looking at apl, I would wager that's much more tenable then what you had to do!

by dimator

4/12/2026 at 9:04:57 AM

For comparison, I heard that people who start with functional programming find it quite intuitive. The hard part isn't learning a new paradigm, but "unlearning" the old one.

(Also I hear they're more than a bit sad about how crude procedural programming is! But unfortunately I came at it the other way around, so my standards are permanently lowered ;)

by andai

4/11/2026 at 9:17:41 PM

At my very first professional EE position, in 1978, there was an older staff member, PhD, kind of a professor type, who was programming in APL. Naturally curious, I asked him about it and what the strange symbols on the keyboard meant. His explanation mostly flew right over my head but I asked a few questions, thanked him, and went away. In 43 years, he's the only person I ever saw using it.

by sizzzzlerz

4/11/2026 at 11:06:18 PM

I've always been curious about APL. My grandfather partnered with an APL programmer in the early 70's to develop shallow geodesic dome geometries suitable for home construction and optimized for least number of distinct strut lengths. The one he lived in is still standing[0]

[0] https://maps.app.goo.gl/YgExrSKh3UZu4XKw9

by seemaze

4/11/2026 at 11:07:38 PM

I used it when I was in college for my Senior Project. That would have been 1978/1979. I had a keyboard with the APL symbols molded onto the keypad.

by garyrob

4/12/2026 at 12:04:37 AM

Well that opened a bit of a rabbit hole. Looking at the source code I saw this which made me chuckle:

    RNUMBER  DC    F'16807'            RANDOM NUMBER.
Surely we wouldn't have DailyWTF quality code here. Looking for how it's referenced we find the RANDOM function itself:

    *        RANDOM NUMBER GENERATOR.
    *        LEHMER'S METHOD, CACM JUNE '66, P 432.
    *        N(I+1) = P RES Q X N(I)
    *        P = (2**31)-1
    *        Q = 7**5
Following that lead to the original ACM article referenced:

https://dl.acm.org/doi/epdf/10.1145/365696.365712

Which further lead to this rather interesting article on the history of the ROLL function which relies on this random number generator:

https://www.jsoftware.com/papers/roll.htm

Neat!

by themafia

4/12/2026 at 4:43:23 AM

If the Keyboard requirements for this language were not so high, I might have gotten into this language, but the cost of purchasing the equipment put me off. That is not to say that I don't find the language intriguing since that it is.

by SilentM68

4/12/2026 at 4:59:11 AM

You can just change keyboard settings in any OS? The same way you change from QWERTY to DVORAK you can change to Cyrillic or... But every APL programmer just uses something like deadkeys, typing e.g. ` before another key like `[ becomes ← or `$ becomes ⍋. The same are largely used for BQN too. Every tutorial teaches how to type explicitly e.g. https://tryapl.org/

If you insist on looking at your keyboard, you can also buy stickers for like $10.

by veqq

4/12/2026 at 5:34:28 AM

Yeah, I changed the keyboard settings in my OS (Win at the time) a few times, but it was a pain to have to remember the key layouts even with tutorials. I like the idea of using stickers at a lower price which is more reasonable. I always wondered why PC engineers did not design Chameleon keyboards with keys that can change their key-designation (LED key shape) based on OS usage per region. I'm sure it's partly due to money. I mean who would not like to have a keyboard that lights up different keys depending on the language you use. There just needs to be a universal key design agreed upon that can accommodate this type of keyboard design.

Don't get me wrong. I like the idea of a compact language and may reconsider APL in the future if, my financial luck changes :)

by SilentM68

4/12/2026 at 6:10:08 AM

There are derivatives of APL, e.g. J, which replace the symbols with ASCII characters, to avoid the keyboard problem:

https://www.jsoftware.com/#/README

I actually prefer a hybrid solution, i.e. using a part of the original APL symbols, which are now provided by Unicode, so you can map them on any standard keyboard as you please, while other symbols are replaced by keywords.

The reason is that a part of the original APL symbols make sense and are useful, because they are extensions of the traditional mathematical notation, while some other symbols, e.g. those used for trigonometric functions, are arbitrary and had only the purpose to make the text somewhat shorter and simplify the parsing of the language at a very early time, when the available resources were very scarce, and this does not matter today any more.

by adrian_b

4/12/2026 at 7:15:10 AM

That gives me the idea of making a sort of transpiler for it as a side project. Maybe I will.

by f1shy

4/12/2026 at 7:05:26 AM

Thank you for the link :)

by SilentM68

4/12/2026 at 4:59:38 AM

A lower cost option is to buy a set of sticker overlays (e.g. similar to the ones you can buy to make it easier to type Korean or Japanese, etc. on a US (or generally, non-native) keyboard).

For example (no affiliation):

https://www.tindie.com/products/russtopia/apl-keyboard-symbo...

by nereye

4/12/2026 at 5:35:02 AM

Thank you for the link :)

by SilentM68

4/12/2026 at 6:05:17 AM

J and K are ASCII-based array languages which were inspired by APL.

by userbinator

4/12/2026 at 7:17:25 AM

Yes, I believe I tried J at one point.

Nothing against the APL, J & K languages but my brain got accustomed to using the R-Language and R-Studio, even over Python, partly because of the same keyboard difficulty, at least in my case, but also because it felt somewhat, more complete, and organized than Python. That's how my brain works, me thinks. Lately, I've started contemplating learning LUA since it's easy to work with and tied to Roblox, for game making, but again, AI's put a pause on all things related to learning, as far as mentally absorbing new stuff is concerned. I don't see the point.

by SilentM68