blog

Power User APL

_2026-05-19

I’m a power user. Here’s how I make Dyalog APL (and other array langs) work for me.

`~/.XCompose`

1st make symbols work.
https://apl.wiki/Typing_glyphs_on_Linux#XCompose_(backtick/prefix/dead_key)
https://mlochbaum.github.io/BQN/editors#xkb-unix
https://github.com/MaxCan-Code/MaxCan-Code/blob/7535c4f9b039c3af16d5d08c0c1f1b02468f8155/symlinks/.XCompose

Shell Pipes

Piping seems to work for all langs. Nice for quick experiments in the shell.

$ echo ⎕se.r⍳3 4\\n]repr ⍳3 4|mapl -b -s
      ⎕se.r⍳3 4
3 4⍴(2⍴1) (1 2) (1 3) (1 4) (2 1) (2⍴2) (2 3) (2 4) (3 1) (3 2) (2⍴3) (3 4)
      ]repr ⍳3 4
(3 4⍴(2⍴1) (1 2) (1 3) (1 4) (2 1) (2⍴2) (2 3) (2 4) (3 1) (3 2) (2⍴3) (3 4))
$ echo ↕3‿4\\n•Repr↕3‿4|bqn
┌─
╵ ⟨ 0 0 ⟩ ⟨ 0 1 ⟩ ⟨ 0 2 ⟩ ⟨ 0 3 ⟩
  ⟨ 1 0 ⟩ ⟨ 1 1 ⟩ ⟨ 1 2 ⟩ ⟨ 1 3 ⟩
  ⟨ 2 0 ⟩ ⟨ 2 1 ⟩ ⟨ 2 2 ⟩ ⟨ 2 3 ⟩
                                  ┘
   "(3‿4⥊⟨0‿0,0‿1,0‿2,0‿3,1‿0,1‿1,1‿2,1‿3,2‿0,2‿1,2‿2,2‿3⟩)"
$ echo '!3 4\n`k(!)3 4'|k
(0 0 0 0 1 1 1 1 2 2 2 2
 0 1 2 3 0 1 2 3 0 1 2 3)
"(0 0 0 0 1 1 1 1 2 2 2 2;0 1 2 3 0 1 2 3 0 1 2 3)"
$ echo "i.3 4\n{{(5!:5)<'y'}}i.3 4\n{{(5!:5)<'y'}}<\"1 i.3 4"|jconsole
0 1  2  3
4 5  6  7
8 9 10 11
i.3 4
0 1 2 3;4 5 6 7;8 9 10 11

Big Arrays

Avoid flooding my screen.

$ echo ⎕se.d⍳2/3 4|mapl -b -s>_
$ echo ↕2/3‿4|bqn>_
$ echo "!,/2#'3 4"|k>_
$ echo i.2#3 4|jconsole>_

More cumbersome way:

$ echo "'_'1⊂⍛⎕nput⍨⎕se.d⍳2/3 4\t"|mapl -b -s
$ echo '"_"•FChars•Fmt↕2/3‿4'|bqn
$ echo "(,\"_\")0:,/'\$!,/2#'3 4"|k
$ echo "(<'_')1!:2~,\":i.2#3 4"|jconsole

In APL session:

$ echo "(⍴,≡)_←⍳2/3 4\t⍝ then ⎕ed'_'"|mapl -b -s
      (⍴,≡)_←⍳2/3 4    ⍝ then ⎕ed'_'
3 3 4 4 2

`~/dyalog.files`

Undocumented. See https://github.com/Dyalog/qSE/blob/561e2c0f9c151fe280f571079f5c3d276f715939/StartupSession.aplf#L160

$ cat ~/dyalog.files/StartupSession/_/_.apln
:namespace _
    ⎕se.(u←Dyalog.Utils) ⋄ ⎕se.(r←u.repObj) ⋄ ⎕se.(d←1 1 0 1∘u.disp) ⋄ #.⎕pw←¯1+2*15
:endnamespace

`~/.inputrc` & `rlwrap`

$ cat ~/.inputrc
# $include /etc/inputrc
set editing-mode vi
set show-mode-in-prompt on
$if term=linux
        set vi-ins-mode-string \1\e[?0c\2
        set vi-cmd-mode-string \1\e[?8c\2
$else
        set vi-ins-mode-string \1\e[6 q\2
        set vi-cmd-mode-string \1\e[2 q\2
$endif

My rlwrap flags:

$ rlwrap -acrm -D 2 mapl -b -s

I used to use these, but global XCompose works better for f/t motions.
https://github.com/mlochbaum/BQN/blob/master/editors/inputrc
https://gist.github.com/0racle/bdaeb945cf42de317a48db7b1529f0fe

Ride Extension

https://github.com/Dyalog/ride/blob/8c89ebbadaae55314d3283818cf999fe4a2cd95a/sample-extensions/vim.js

APLK

Also undocumented. I dug into it for work. See https://docs.dyalog.com/20.0/unix-installation-and-configuration-guide/configuration-parameters/environment-variables#_table-1

Proof of concept:
$ echo ",⍤¯1⊃⊃⎕shell'diff -u \$DYALOG/aplkeys default'|mapl -b -s"

-M0=Nrm:
+M0=Ins:    ,    ,, 105
+M3=Nrm:  27
-,UC:		27 91 65	+ Up cursor
-,DC:		27 91 66	+ Down Cursor
-,RC:		27 91 67	+ Right Cursor
-,LC:		27 91 68	+ Left Cursor
+,UC:		27 91 65,,,107	+ Up cursor
+,DC:		27 91 66,,,106	+ Down Cursor
+,RC:		27 91 67,,,108	+ Right Cursor
+,LC:		27 91 68,,,104	+ Left Cursor
-,EP=Esc:	27		+ EscaPe
+,EP=Esc:	,,,27		+ EscaPe

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Power User APL

~/.XCompose