Alan Kay on “What Made APL Programming So Revolutionary?” | Hacker News Reader

Alan Kay on “What Made APL Programming So Revolutionary?”

quora.com

53 pointsfniephaus14 comments

I programed in APL! Sure, I just had to change an already developed code from my MSc adviser. It was weird! First of all, you needed an special keyboard just to use it: http://ageinghacker.net/hacks/apl-keyboard/apl-keyboard-1.jp...

When you were not fluent, the myriad different symbols would overload your working memory, making it very hard to program. Just needing to find the symbols in the keyboard would make you program slowly. It had some nice ideas about matrix programming, probably they are similar of pandas or tidy verse. Cool, but the steeeeep learning were really terrible.

Read the article! Great reminiscences from one of greatest computer science elders. Made me understand better the language.

This code example (Nile language not APL) makes me want to look into those languages:

https://qph.fs.quoracdn.net/main-qimg-07327016425ac646009769...

I think its so beautiful, just the math written down.

I always liked this example: Conway's Game of Life in One Line of APL https://www.youtube.com/watch?v=a9xAKttWgP4 It's esoteric as one-liners tend to be, but I think it's a fascinating glimpse.

Since Alan Kay mentioned Nile, I'm gonna dump here the list of relevant resources on Nile and its derivative works that I've found over time:

Ohm, the successor to the parser (Ometa) used by Nile: https://github.com/harc/ohm

Maru, Nile's compiler/interpreter/whatever: https://www.reddit.com/r/programming/comments/157xdz/maru_is...

Nile itself: https://github.com/damelang/nile (pdf presentation in README) https://programmingmadecomplicated.wordpress.com/2017/10/11/...

Gezira, svg drawing lib on top of Nile: https://github.com/damelang/gezira/blob/master/nl/stroke.nl http://web.archive.org/web/20160310162228/http://www.vpri.or... https://www.youtube.com/watch?v=P97O8osukZ0 https://news.ycombinator.com/item?id=8085728 (check the demo video) https://www.youtube.com/watch?v=ubaX1Smg6pY (live demo on stage later on) https://github.com/damelang/gezira/tree/master/js/demos (downloadable and runnable in browser)

KScript, UI building on top of Nile: https://www.freudenbergs.de/bert/publications/Ohshima-2013-K... http://tinlizzie.org/dbjr/KSWorld.ks/

Final Viewpoint Research Institute report, where the entire system (antialiasing, font rendering, svg, etc) was rendered using Nile into Frank, the word/excel/powerpoint equivalent written completely in Nile + Gezira + KScript): http://www.vpri.org/pdf/tr2012001_steps.pdf

VPRI wiki restored from archive.org: https://web.archive.org/web/20171121105004/http://www.vpri.o...

Shadama, which the Nile author (Dan Amelang) worked on too: https://2017.splashcon.org/event/live-2017-shadama-a-particl...

Partial DOM reimplementation on top of Gezira: https://github.com/damelang/mico/blob/master/gezira/svg.js

Partial reimplementation of Gezira: https://github.com/Twinside/Rasterific

And the famous Nile Viewer itself (everything interactive): http://tinlizzie.org/dbjr/high_contrast.html https://github.com/damelang/nile/tree/master/viz/NileViewer

Commentary: http://lambda-the-ultimate.org/node/4325#comment-66502 https://fonc.vpri.narkive.com/rtIMYQdk/nile-gezira-was-re-1-... http://forum.world.st/Vector-Graphics-was-Pi-performance-fun...

Since Alan Kay himself is on Hacker News, maybe he can comment with more links I couldn't find. It's hard to fire up the live Frank environment, though understandably reproducing the working env might not have been a top goal. Maybe someone more cunning can merge these into a single executable repo or whatever so that I can stop playing archaeologist =)

Kay: > There are several modern APL-like languages today — such as J and K — but I would criticize them as being too much like the classic APL. It is possible to extract what is really great from APL and use it in new language designs without being so tied to the past.

It would've been good to see specific criticism instead of being just like classic APL.

I think many of APL/k/j verbs/adverbs can be generalized to working on streams (dataflow programming). Perhaps Dan Amelang's very interesting work on "2.5D" graphics can be cast into such an extended version....

I have played with both Nile and APL now for a bit, and I have been thinking about how to combine them. I believe if we took Nile's operator overloading, tick syntax (s' is the previous value of s), and recursion being expressed via streams (<< operator), and combined it with some of the higher order adverbs of apl, it might be very interesting. In APL complex structures (say a point, or a bezier curve) need to be broken up into constituent equal length arrays for processing, but I believe one could just overload basic operations like +, - , etc.

Do you have an easy way to set up Nile and get it running? And did you run Frank too?

No I ran it mainly from from Bret Victors viz directory. Did not run Frank. Would be interesting to build a Nile runtime in go or elixir (maps well to [processes), with a simple compiler in Ocaml.

By viz directory did you mean https://github.com/damelang/nile/tree/master/viz/NileViewer

And yeah, it'd interesting to build one. Is there enough info on it to build such compiler though? That NileVM.js is helpful. I've posted a list of resources in another comment below, but maybe I've missed a few

The Nile compilers directory has a bunch of stuff in JavaScript, Smalltalk as well as in Maru (which is in itself pretty interesting, and is a self hosted lisp)

I am more familiar with k so will use it as an example. If we were to extend it, the equivalent of some functions in compositor.nl would be something like this:

  compositeSrc:{x} // output first arg
  compositeDst:{y} // output second arg
  compositeInvert:{+(1-x[;0];1-x[;1];1-x[;2];x[;3])}
  // take a column, invert r, g, b columns and transpose

where x[i;0 1 2 3] == ith (r,g,b,a) of x. No need for "∀ (A, B) >>". This is implicit as k/APL work on whole collections. Basic operations are already overloaded. There would need to be a way to define tuples. "x[i;2]" to refer to ith blue value is a bit cryptic. You can define verb "blue x[i]" to do the same but may be some language syntax would help. I can't grasp enough of Nile through the examples I've seen so far but seems doable.

If you take a look at things like converting beziers into sub-beziers of specific flatness, you could express it pretty easily as a // convergence as in k, or a power operator in apl, but it would be really nice to have the notion of an algebra of points. So if the distance between two points is b - a, then +/ eachprior {y-x} would give us the total length of a polyline.

This can get a bit tricky. You can do something like this today:

  d:{_sqrt+/(y-x)^2}
  ls: 2 10 # 20 _draw 0 // a list of 10 random points
  +/d':ls // total length

Now if x, y above are vectors of points (as opposed to vectors of pairs), and if points have their own - verb, total length becomes "+/{y-x}':ls". But to define such a - for point, you'd need conversion verbs (or enclose/disclose).

Holy Sh*t! A lot of things to do and I just discovery Alan Kay's answers in Quora: https://www.quora.com/profile/Alan-Kay-11

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