"learn Apl" Notes

Posted2 months agoActive2 months ago

todsacerdoti

50 points

10 comments

luksamuk.codesTechstory

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AplProgramming LanguagesUnicode

Key topics

Apl

Programming Languages

Unicode

The 'Learn APL' resource is shared, sparking discussion about APL's history, usage, and encoding, with users sharing their experiences and tips for working with the language.

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Oct 25, 2025 at 4:34 PM EDT
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Discussion (10 comments)

Showing 10 comments

smartmic

2 months ago

2 replies

I worked with GNU APL for a while and really liked it. It's also possible to extend it with the C foreign function interface (FFI). The best way I found to input the APL2 symbols with my normal keyboard was with a customized XCompose definition where the input chords are mnemonics of the actual symbols: https://gist.github.com/smartmic/cdb8b0b3936ab965213748813b6...

bear8642

2 months ago

1 reply

huh, can you not use the Xkb APL symbols file?

I thought that compose definitions as well as the shifted layout…

ofalkaed

2 months ago

You can and most do but some people go other routes for one reason or another.

https://aplwiki.com/wiki/Typing_glyphs

turtleyacht

2 months ago

1 reply

Thank-you. Any thoughts on the layout below versus the others listed?

https://www.pckeyboard.com/page/product/USAPLSET

I've got some notes on setting up input on OpenBSD as well. It enables Left Ctrl and Left Alt for APL symbols, but also a Unicode escape hatch with Right Alt and Caps Lock: https://github.com/turtleyacht/ap-el-kb.github.io

ofalkaed

2 months ago

It looks to be the standard Dyalog APL keyset, which will be just fine for GnuAPL and most if not all APLs but not all languages of the APL family.

mmooss

2 months ago

3 replies

APL was developed in the 1960s. Between then and whenever its symbols were added to Unicode (U+2336 and following, at least), how were its symbols encoded?

7thaccount

2 months ago

Early on, the selectric typewriter thing had a spherical ball that could rotate to stamp the characters. So when you typed a key the IBM hardware would type a character on a piece of paper exactly like a typewriter and also the IBM computer would keep track of this and when you ran the expression it would calculate the result and print that out as well. You can see videos of this.

electroly

2 months ago

I believe it depends on the era and system, but there were various APL codepages (i.e. definitions for the upper 128 characters) for both EBCDIC and ASCII.

https://en.wikipedia.org/wiki/Digital_encoding_of_APL_symbol...

In the very earliest IBM Selectric teletype-based systems, some APL symbols were constructed by entering one character, hitting backspace, and overstriking a second character. For instance, ⍋ is | overstruck on ∆. It's why a lot of APL symbols look like that.

https://aplwiki.com/wiki/Overstrike

dzaima

2 months ago

Custom encodings, as was standard (or, well, mandatory) before Unicode (1991). Hell, Dyalog APL to this day supports its classic 1-byte-per-char encoding (not even ASCII-compatible! Nor EBCDIC!) in addition to Unicode.

Looks like the APL chars were added in Uncicode 1.1 (1993), two years after 1.0, which is quick enough.

throwaway81523

2 months ago

Old RMS song, to the tune of "row row row your boat":

Rho, rho, rho of x, always equals 1

Rho's dimension, rho rho rank; APL is fun!

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ID: 45706755Type: storyLast synced: 11/20/2025, 1:08:48 PM

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