The APL Orchard

11:22 AM

Christmas came a bit early at #Dyalog ... new toys and an APL joke! 4⍴○3 new build #raspberrypi running on @BitScopeDesigns blade

Tweeted by dyalogapl on December 6, 2017 at 11:19 AM

Uriel

12:27 PM

@Adám what do I need to put in tio header to show box display?

I tried the things you sent to tio bot and they failed

Adám

@Uriel Verbatim from tio bot.

Uriel

@Adám oh, apparentaly I put io←0 before that code, rather then after, and that's why it failed

Adám

12:43 PM

@Uriel Yes, Dyalog code assumes ⎕IO←1 and here we copy a function out of its context so the function expects ⎕IO←1 but gets 0.

To participate in tonight's learning session without 20 Stack Exchange rep points, click lower-left giant avatar, then click "user profile" and there will be a number in the URL; that's your chat ID. Email your chat ID to adam@ with the domain being dyalog.com.

Uriel

@Adám hmm I would expect core functions to save io on entry and restore on exit when specific one needed (no critisism intended, it just might cause bugs for real world users)

Adám

@Uriel Utility functions, yes. Functions from the dfns workspace handle ⎕IO variations, but enableSALT was never intended to be run like that. Usually SALT is enabled at start-up. However, TIO runs a bare-bones system for performance.

Erik the Outgolfer

12:59 PM

@Feeds what, why pi * 3, pi * 3, pi * 3, pi * 3?

how is that related to christmas, hmm

Adám

1:27 PM

@EriktheOutgolfer We got four (Raspberry) Pi 3s (as "presents").

Feeds

2:50 PM

Adám is hosting another informal APL learning session tonight at 18:30 UTC in https://chat.stackexchange.com/rooms/52405/apl , continuing the previous week's "APL primitive functions' marathon". See https://chat.stackexchange.com/transcript/message/41299896#41299896 … if you don't have 20 Stack Exchange rep points.

Tweeted by dyalogapl on December 6, 2017 at 2:33 PM

Adám

6:30 PM

Welcome to the APL learning session!

We're in the middle of our functions' marathon. Next up is ⍋, called "Grade".

HyperNeutrino

First time here, any quick notes on what I should know in terms of prior knowledge to the language or classroom etiquette?

Adám

Note that you can follow the second link on the right to install a language bar, and key bindings so that you can easily type APL characters.

@HyperNeutrino You can find previous lessons here. Only really lesson 1 is necessary.

HyperNeutrino

Ah okay, thanks!

Adám

Please feel free to interrupt with any questions.

Monadic ⍋ takes a simple (non-nested) array and returns the indices of the major cells reordered so that they would order the array.

Easiest to understand with an example:

⍞←⍋3 1 4 1 5

Dyalog APL

@Adám 2 4 1 3 5

Adám

6:37 PM

This means that the second element (1) is the smallest, then the fourth (1), then the first (3), etc.

So, we can use this to sort the array:

⍞←3 1 4 1 5[⍋3 1 4 1 5]

Dyalog APL

@Adám 1 1 3 4 5

HyperNeutrino

so grade(a)=b means that a[x] for x in b is the same as sorted(a)?

Adám

@HyperNeutrino Exactly. Also, use the language bar so you can have proper APL characters.

HyperNeutrino

ooh ok I'll install that right now

oh this is equivalent to jelly Ụ :D

Adám

@HyperNeutrino However, you don't need the loop (for x in b) as APL allows indexing with an array, and the result has the same shape as the indexing array.

HyperNeutrino

6:39 PM

ah ok I see how this works

Adám

@HyperNeutrino Well, I bet the U stands for "Grade Up". Jelly comes from J which comes from APL.

HyperNeutrino

Yeah. That seems to make the most sense.

Adám

It works on high-rank arrays too:

⎕←3 2⍴2 7 1 8 2 8

Dyalog APL

@Adám
2 7
1 8
2 8

Adám

⎕←⍋3 2⍴2 7 1 8 2 8

Dyalog APL

6:41 PM

@Adám
2 1 3

Adám

So the first is row 2 (1 8) then row 1 (2 7) then row 3 (2 8).

HyperNeutrino

so the ordering of the arrays is lexicographical or something?

Adám

@HyperNeutrino Yes.

HyperNeutrino

Okay

Adám

Works on characters too, where it grades in Unicode point order:

⎕←5 2⍴'HelloWorld'

Dyalog APL

6:42 PM

@Adám
He
ll
oW
or
ld

Adám

⎕←⍋5 2⍴'HelloWorld'

Dyalog APL

@Adám
1 5 2 3 4

Adám

⎕←(5 2⍴'HelloWorld')[⍋5 2⍴'HelloWorld';]

Dyalog APL

@Adám
He
ld
ll
oW
or

HyperNeutrino

⎕←2 2 2⍴⍳8

Dyalog APL

6:44 PM

@HyperNeutrino
1 2
3 4

5 6
7 8

HyperNeutrino

⎕←⍋222⍴⍳8

Dyalog APL

@HyperNeutrino
1 9 17 25 33 41 49 57 65 73 81 89 97 105 113 121 129 137 145 153 161 169 177 185 193 201 209 217 2 10 18 26 34 42 50 58 66 74 82 90 98 106 114 122 130 138 146 154 162 170 178 186 194 202 210 218 3 11 19 27 35 43 51 59 67 75 83 91 99 107 115 123 131 139 147 155 163 171 179 187 195 203 211 219 4 12 20 28 36 44 52 60 68 76 84 92 100 108 116 124 132 140 148 156 164 172 180 188 196 204 212 220 5 13 21 29 37 45 53 61 69 77 85 93 101 109 117 125 133 141 149 157 165 173 181 189 197 205 213 221 6 14 22 30 38 46 54 62 70 78 86 94 102 110 118 126 134 142 150 158 166 174 182 190 198 206 …

HyperNeutrino

no wait

⎕←⍋2 2 2⍴⍳8

Dyalog APL

@HyperNeutrino
1 2

Adám

@HyperNeutrino First layer, second layer.

HyperNeutrino

6:45 PM

Did I do something wrong?

wait nvm

Adám

@HyperNeutrino No, that's right.

HyperNeutrino

oh right. that makes sense thanks

Adám

⎕←4 2 2⍴'Hello World PPCG'

Dyalog APL

@Adám
He
ll

o
Wo

rl
d

PP
CG

Adám

⎕←⍋4 2 2⍴'Hello World PPCG'

Dyalog APL

6:46 PM

@Adám
1 4 2 3

Adám

Layer 1, layer 4, layer 2, layer 3.

⎕←{⍵[⍋⍵;]}4 2 2⍴'Hello World PPCG'

Dyalog APL

@Adám

Rebuilding user command cache... done
Was OFF -trains=box -fns=off
⍎RANK ERROR
 __field_initialize_result_←(⎕NS ⍬).⍎'⎕CY''salt''⋄⎕SE.UCMD''box on -fns=on -trains=tree''⊣enableSALT' ⋄ ⎕←{⍵[⍋⍵;]}4 2 2⍴'Hello World PPCG'
                                                                                                        ∧

Real time: 1.177 s
User time: 1.069 s
Sys. time: 0.046 s
CPU share: 94.81 %
Exit code: 0

HyperNeutrino

how do you type backticks

Adám

@HyperNeutrino backtick,space

⎕←{⍵[⍋⍵;;]}4 2 2⍴'Hello World PPCG'

Dyalog APL

@Adám
He
ll

PP
CG

o
Wo

rl
d

HyperNeutrino

6:47 PM

:D cool thanks! also tab backtick seems to work for some reason (I accidentally found that out lol :P)

Adám

@HyperNeutrino Interesting, unintentional, useful.

@all Anything else about monadic ⍋?

HyperNeutrino

⎕←⍋⍋4 2 5 1 3

Dyalog APL

@HyperNeutrino
4 2 5 1 3

HyperNeutrino

⎕←⍋4 2 5 1 3

Adám

@HyperNeutrino Cardinal numbers.

HyperNeutrino

6:49 PM

?

RosLuP

⎕←⎕←3

Adám

@HyperNeutrino ⍋⍋ is the cardinal numbers:

Dyalog APL

@RosLuP
3
3

HyperNeutrino

oh lol

Adám

⍞←⍋'PPCG'

Dyalog APL

6:50 PM

@Adám 3 4 1 2

Adám

⍞←⍋⍋'PPCG'

@DyalogAPL Hello?

⍞←⍋⍋'PPCG'

Dyalog APL

@Adám 3 4 1 2

HyperNeutrino

what's the difference between ⍞ and ⎕?

I don't quite understand cardinal numbers..

Adám

So P is the third, P is the fourth, C is the first, and G is the second.

Erik the Outgolfer

@Adám hello, had to study...

Adám

6:52 PM

@HyperNeutrino ⍞← makes an inline response of the first line of the output, and without box drawing characters. ⎕← makes a multi-line response with boxed display.

Zacharý

@Adám I thought those were ordinals? Or are you referring to what they return as ordinals?

HyperNeutrino

ooh okay, thanks!

RosLuP

⎕←⍋2 2 2, 4 5 6

Dyalog APL

@RosLuP
1 2 3 4 5 6

HyperNeutrino

@RosLuP (2 2 2) (4 5 6)?

Adám

6:53 PM

@RosLuP 2 2 2, 4 5 6 is the same as 2 2 2 4 5 6

HyperNeutrino

⎕←⍋ ⍋ 4 2 5 1 3

Dyalog APL

@HyperNeutrino
4 2 5 1 3

Erik the Outgolfer

@Adám wait huh

Adám

@RosLuP ⎕←2 3⍴2 2 2, 4 5 6

HyperNeutrino

does putting a space between the two ⍋ help?

Erik the Outgolfer

6:53 PM

how does grade up multiple times return cardinal numbers...I thought it was just the same as grade up once

Adám

@HyperNeutrino Between what?

@EriktheOutgolfer It is so that the grade of the grade is the cardinal numbers. That is in the nature of grading.

HyperNeutrino

oh I think I get why. grading my test list returns the list itself :P

⎕←⍋ ⍋ 3 5 4 1 2

Dyalog APL

@HyperNeutrino
3 5 4 1 2

Adám

@HyperNeutrino Yes, if your numbers are all the integers from 1 to n.

HyperNeutrino

my numbers were 4 2 5 1 3

Adám

6:55 PM

@HyperNeutrino Because 3 is the third, and 5 the fifth.

HyperNeutrino

yeah :P

Zacharý

So grade grade returns the numbers fitted to 1 ... length(list)?

HyperNeutrino

it was a product of distinct swaps

Erik the Outgolfer

@Adám um how does ⍋⍋ differ from just ⍋

HyperNeutrino

if you continue applying ⍋ multiple times eventually it will form a cycle. I wonder if the period of the cycle has anything to do with the original list

Adám

6:56 PM

@Zacharý So applying ⍋ to a permutation inverts it (swaps between cardinal and grade)

RosLuP

⎕←2 3⍴2 2 2, 4 5 6

Dyalog APL

@RosLuP
2 2 2
4 5 6

Adám

@HyperNeutrino The period is 2.

HyperNeutrino

oh

well then :P

)about

Dyalog APL

@HyperNeutrino You can evaluate an APL expression by typing it into chat prefixed by ⍞←. Use ⎕← instead for boxed display and multi-line results. Do not use markdown. Commands: )lb for language bar, )help for table of language elements, )docs for full documentation, )ref for PDF reference card.

HyperNeutrino

6:57 PM

that's an interesting command syntax for a chatbot :P the unmatched parentheses are bugging me :P

Adám

@EriktheOutgolfer ⍋ is the indices of cells in the order that would sort them. ⍋⍋ is the position each will take when sorted. If you think about it hard, you'll see what ⍋ swaps back and fort between these two.

Zacharý

@HyperNeutrino That's APL

Adám

@HyperNeutrino In APL, all non-syntactic system commands begin with )

HyperNeutrino

ooh okay, interesting

Erik the Outgolfer

@Adám oh so it's the same, but different explanation?

Adám

6:59 PM

@HyperNeutrino It clearly tells the system that this line is not an APL statement.

RosLuP

⎕←2 3⍴2 2 2 4 5 6

Dyalog APL

@RosLuP
2 2 2
4 5 6

HyperNeutrino

cool ok

Adám

@EriktheOutgolfer No. they are different ways to state how an array is ordered.

@HyperNeutrino Dyalog APL System Commands.

Erik the Outgolfer

@Adám can you please give an example where they are different? everything I've ever tried it on makes it look like they're equivalent...

Adám

7:01 PM

⎕←⍋'random' ⋄ ⎕←⍋⍋'random'

Dyalog APL

@Adám
2 4 6 3 5 1
6 1 4 2 5 3

Erik the Outgolfer

hmm

HyperNeutrino

so ⍋ once is what order the elements would be in when sorted and ⍋ twice is the indices that each element would go to?

Adám

@EriktheOutgolfer ^ Column 1 says: the "lowest" letter is number two (a) while r is the sixth.

@HyperNeutrino Exactly. Bravo!

HyperNeutrino

:D

Erik the Outgolfer

7:03 PM

⎕←⍋'aedcb'⋄⎕←⍋⍋'aedcb'

Dyalog APL

@EriktheOutgolfer
1 5 4 3 2

Erik the Outgolfer

duh

Zacharý

⍋⍋⍋ is equivalent to ⍋, right?

Erik the Outgolfer

⎕←⍋'aedcb'⋄⎕←⍋⍋'aedcb'

Dyalog APL

@EriktheOutgolfer
1 5 4 3 2
1 5 4 3 2

Adám

7:04 PM

@Zacharý Yes.

Erik the Outgolfer

⎕←⍋'edcba' ⋄ ⎕←⍋⍋'edcba'

HyperNeutrino

lol if the input list can be represented as a product of disjoint 2-cycles applied to its sorted version then ⍋ and ⍋⍋ do the same thing xD

Dyalog APL

@EriktheOutgolfer
5 4 3 2 1
5 4 3 2 1

Erik the Outgolfer

duuuh

HyperNeutrino

⎕←⍋'bcdea'⋄⎕←⍋⍋'bcdea'

Dyalog APL

7:05 PM

@HyperNeutrino
5 1 2 3 4
2 3 4 5 1

Erik the Outgolfer

⎕←⍋'eadbc' ⋄ ⎕←⍋⍋'eadbc'

Dyalog APL

@EriktheOutgolfer
2 4 5 3 1
5 1 4 2 3

Erik the Outgolfer

so I guess it must have these two properties to be different

Adám

@all Can we move on to dyadic ⍋?

Erik the Outgolfer

⎕←⍋'aebdc' ⋄ ⎕←⍋⍋'aebdc'

Dyalog APL

7:06 PM

@EriktheOutgolfer
1 3 5 4 2
1 5 2 4 3

@Adám sure

Yes

sure

⎕←⍋⍋'123456789'⋄ ⎕←⍋'123456789'

Dyalog APL

@RosLuP
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9

Adám

7:09 PM

Actually, one more thing:

Since ⍋ inverts itself, it is it's own inverse:

RosLuP

⍋⍋a=⍋a only if a is sorted

HyperNeutrino

not necessarily

Adám

⍞←⍋6 1 4 2 5 3

Dyalog APL

@Adám 2 4 6 3 5 1

Adám

(⍋⍣¯1)6 1 4 2 5 3

Erik the Outgolfer

7:10 PM

@RosLuP not always the case, sometimes that's true even when a isn't sorted

Adám

⍞←(⍋⍣¯1)6 1 4 2 5 3

Dyalog APL

@Adám 2 4 6 3 5 1

Adám

f⍣¯1 is inverse of f.

HyperNeutrino

I hypothesize that ⍋⍋a=⍋a if and only if a can be sorted by only applying swaps without moving any element more than once

⎕←⍋5 1 4 2 3 ⋄ ⎕←⍋⍋5 1 4 2 3

Dyalog APL

@HyperNeutrino
2 4 5 3 1
5 1 4 2 3

HyperNeutrino

7:11 PM

wait

i'm dumb

⎕←⍋4 2 3 1 6 5 ⋄ ⎕←⍋⍋4 2 3 1 6 5

Dyalog APL

@HyperNeutrino
4 2 3 1 6 5
4 2 3 1 6 5

Erik the Outgolfer

⎕←⍋2 1 4 3 5 ⋄ ⎕←⍋⍋2 1 3 4 5

Dyalog APL

@EriktheOutgolfer
2 1 4 3 5
2 1 3 4 5

Erik the Outgolfer

⎕←⍋2 1 4 5 3 ⋄ ⎕←⍋⍋2 1 4 5 3

Dyalog APL

@EriktheOutgolfer
2 1 4 3 5
2 1 4 3 5

Erik the Outgolfer

7:13 PM

⎕←⍋2 1 4 5 3 ⋄ ⎕←⍋⍋2 1 4 5 3

Dyalog APL

@EriktheOutgolfer
2 1 5 3 4
2 1 4 5 3

HyperNeutrino

it might seem that ⍋a=⍋⍋a iff ⍋a=a but that doesn't work when a doesn't contain all 1 to length(a)

⍋⍣¯1

RosLuP

⎕←⍋ 1 2 4 5 ⋄ ⎕←⍋⍋ 1 2 4 5

Dyalog APL

@RosLuP
1 2 3 4
1 2 3 4

Zacharý

Or a isn't a vector of numbers

Adám

7:14 PM

Anyway, let's move on.

HyperNeutrino

true

okay :D

Adám

Dyadic ⍋ is for character arrays only, and it grades as if the left argument was the alphabet:

⍞←{⍵['aeioubcdfghjklmnpqrstvwxyz'⍋⍵]}'helloworld'

Dyalog APL

@Adám eoodhlllrw

HyperNeutrino

wait so is this essentially sort to a specific order?

Adám

@HyperNeutrino Yes, but a bit more fancy. I'll show.

HyperNeutrino

7:16 PM

okay

⎕←'dbcafe'⍋'abcdef'

Dyalog APL

@HyperNeutrino
4 2 3 1 6 5

HyperNeutrino

⎕←4 2 3 1 6 5⍋1 2 3 4 5 6

Dyalog APL

@HyperNeutrino

Rebuilding user command cache... done
Was OFF -trains=box -fns=off
⍎DOMAIN ERROR
 __field_initialize_result_←(⎕NS ⍬).⍎'⎕CY''salt''⋄⎕SE.UCMD''box on -fns=on -trains=tree''⊣enableSALT' ⋄ ⎕←4 2 3 1 6 5⍋1 2 3 4 5 6
                                                                                                        ∧

Real time: 1.096 s
User time: 1.020 s
Sys. time: 0.044 s
CPU share: 97.00 %
Exit code: 0

HyperNeutrino

pffft

I expected that though :P

Erik the Outgolfer

it only works for char arrays

HyperNeutrino

7:17 PM

yeah

Zacharý

So how come dyadic ⍋ isn't able to work on numeric arrays? Is there a specific reason?

Erik the Outgolfer

@Adám

Adám

If characters are missing from the alphabet, they will be considered after the alphabet, and equivalent:

⍞←'abcdefgh'⍋'hawl'

Dyalog APL

@Adám 2 1 3 4

HyperNeutrino

⍞←''⍋'hello world'

Dyalog APL

7:19 PM

@HyperNeutrino 1 2 3 4 5 6 7 8 9 10 11

Adám

@Zacharý It would be possible, I guess, but not very meaningful.

Dyadic ⍋ can also use multiple levels of sorting:

⎕←⍉↑'aeiou' 'bcdfghjklmnpqrstvwxyz'

Dyalog APL

@Adám
ab
ec
id
of
ug
 h
 j
 k
 l
 m
 n
 p
 q
 r
 s
 t
 v
 w
 x
 y
 z

Adám

This 2D "alphabet" means that all vowels should come before all consonants, and only if otherwise the same, the vertical order will be considered.

Zacharý

@HyperNeutrino so ''⍋⊢ is ⍳∘⍴ (at least for rank 1)

Adám

@Zacharý Yes, that's nice for golfing. Never thought of that. ⍬⍋ is shorter and dyadic too (good for trains).

⍞←{⍵[(⍉↑'aeiou' 'bcdfghjklmnpqrstvwxyz')⍋⍵]}'helloworld'

Dyalog APL

7:22 PM

@Adám eoodhlllrw

Adám

So this sorted all vowels before all consonants, and only then did it sort the vowels and the consonants.

HyperNeutrino

ooh that's cool

anyway brb o/

Zacharý

⍞←{⍵[(⍉↑'aeiou' 'ebcdfghjklmnpqrstvwxyz')⍋⍵]}'helloworld'

Dyalog APL

@Zacharý eoodhlllrw

Erik the Outgolfer

@Adám oh so ⍬ won't cause a DOMAIN ERROR

Zacharý

7:24 PM

⍞←{⍵[(⍉↑'aeiou' 'bcdfghjklmnpqrstvwxyze')⍋⍵]}'helloworld'

Dyalog APL

@Zacharý eoodhlllrw

Adám

And you can have up to 15 levels of sorting using this.

Zacharý

⍞←{⍵[(⍉↑'aeiou' 'bcdfghjklmnpqrstvwxyzo')⍋⍵]}'helloworld'

Dyalog APL

@Zacharý eoodhlllrw

Adám

@Zacharý If a letter occurs more than once, then its first occurrence rules. This is useful to fill gaps in (e.g.) columns of unequal height.

@all I think that's it for ⍋. Any questions?

Zacharý

7:27 PM

Then what is the difference between {⍵[(⍉↑'aeiou' 'bcdfghjklmnpqrstvwxyz')⍋⍵]} and {⍵[('aeiou','bcdfghjklmnpqrstvwxyz')⍋⍵]}

HyperNeutrino

what are the main uses of ⍋ in real-life/practical usage?

Erik the Outgolfer

@Adám yes

Adám

@HyperNeutrino Sorting.

Erik the Outgolfer

I don't see a reason why it should be limited to 15 levels?

it's not like each level adds one dimension to the array is it?

HyperNeutrino

wait is there no sort monad?

Erik the Outgolfer

7:28 PM

@HyperNeutrino no

Zacharý

@EriktheOutgolfer Same reason as arrays having max 15 ~~depth~~ rank maybe?

Adám

@EriktheOutgolfer Because the level increases the rank by one, and Dyalog arrays can max have rank 15.

Erik the Outgolfer

@Adám oh it does?

Adám

@Zacharý Rank, not depth. Depth may be infinite (bound by memory only).

Erik the Outgolfer

(btw Adám's pings are silent for some reason, but not others')

(and that bothers me a little bit because, well, ...)

Adám

7:30 PM

@EriktheOutgolfer I turned my ping sounds off. Wonder if chat is broken.

@EriktheOutgolfer How about now?

Erik the Outgolfer

yes now they're audible

btw I don't think by turning your pings sounds off it should be silent for me too

Adám

@EriktheOutgolfer Silent?

Erik the Outgolfer

@Adám yes, I think so :/ chat is notoriously buggy btw

Adám

@HyperNeutrino No, but I've argued that there should be one.

@EriktheOutgolfer Loud?

HyperNeutrino

I really think there should :P

Adám

7:32 PM

@HyperNeutrino Why?

Zacharý

Golfing (Even though APL is not meant for golfing)

Erik the Outgolfer

@HyperNeutrino btw the shortest you can get to a short monad for anything is {⍵[⍋⍵]}

HyperNeutrino

well golfing and because having a sort builtin would be so much nicer than {⍵[⍋⍵]}

Adám

@Zacharý CXO says: APL is not a golfing language. Sorry!

Erik the Outgolfer

so simply sorting a list is now to be considered something only useful for golfing languages?

Zacharý

7:34 PM

Yeah I know, that would be a reason it would be nice, along with ease of typing (rather than typing {⍵[⍋⍵]} every time)

Adám

@EriktheOutgolfer It doesn't even sort everything, only simple vectors.

Zacharý

What would be the shortest method for sorting everything then?

HyperNeutrino

wait what does simple vector mean in this context?

Adám

@Zacharý J has it better: J's A⍋B is APL's B[⍋A] so you can sort B with B⍋B or ⍋⍨B.

@HyperNeutrino A non-nested list.

HyperNeutrino

but ⍋2 3⍴3 3 6 5 3 2 works?

Adám

7:37 PM

@HyperNeutrino That has rank 2 but depth 1. It isn't nested, it just has two dimensions.

Zacharý

How does that work, anyways? And how many chars is J's equivalent to ⍋.

HyperNeutrino

oh?

RosLuP

What if for sorting one array one has need to use a special function compare? For example, Axiom has sort(compfunction,arrayObj) if I remember well

HyperNeutrino

⎕←⍋1 2 3 (4 5 6) 7 8 9

Adám

@Zacharý Two.

Dyalog APL

7:37 PM

@HyperNeutrino

Rebuilding user command cache... done
Was OFF -trains=box -fns=off
⍎DOMAIN ERROR
 __field_initialize_result_←(⎕NS ⍬).⍎'⎕CY''salt''⋄⎕SE.UCMD''box on -fns=on -trains=tree''⊣enableSALT' ⋄ ⎕←⍋1 2 3(4 5 6)7 8 9
                                                                                                        ∧

Real time: 1.150 s
User time: 1.070 s
Sys. time: 0.038 s
CPU share: 96.38 %
Exit code: 0

HyperNeutrino

ah okay

Zacharý

@RosLuP I don't think there is an operator for that.

Adám

@HyperNeutrino That's a seven element list. It has rank 1, depth ¯2 (negative because it is unevenly nested)

HyperNeutrino

ah ok

Adám

@Zacharý {⍵⌷⍨⊂⍋↑⍣≡⍵} is the shortest I've found that can sort any array that has no refs, is homogeneous, and where 15≥⍴∘⍴+|∘≡

Next one will be quick: ⍒ is the same as ⍋ but grades descending.

Zacharý

7:41 PM

⎕←{⍵⌷⍨⊂⍋↑⍣≡⍵}(1 2)(3 4)

Dyalog APL

@Zacharý
┌───┬───┐
│1 2│3 4│
└───┴───┘

Zacharý

⎕←{⍵⌷⍨⊂⍋↑⍣≡⍵}(3 4)(1 2)

Erik the Outgolfer

@Adám well, I don't get that, if a builtin was added for that, why shouldn't a builtin for sorting a list shouldn't, that looks more like a golfing feature than a simple sort does...

Adám

@EriktheOutgolfer What? Can you fix your grammar?

Zacharý

⎕←2

Erik the Outgolfer

7:42 PM

sorry

Dyalog APL

@Zacharý
2

Zacharý

⎕←{⍵⌷⍨⊂⍋↑⍣≡⍵}(3 4)(1 2)

Dyalog APL

@Zacharý
┌───┬───┐
│1 2│3 4│
└───┴───┘

Zacharý

Wait, what are refs?

Erik the Outgolfer

@Adám I meant that, if there is such a built-in (⍒), then I can't get why a sort built-in doesn't exist as well, since IMO ⍒ is more of a golfing feature than a simple sort builtin

Adám

7:44 PM

@Zacharý Pointers to objects. That's for the OOP lesson…

Zacharý

@Adám I'll need to be there for that one.

Adám

@EriktheOutgolfer Do ⍒'HelloWorld' using ⍋!

HyperNeutrino

⎕←⍋'HelloWorld' ⋄ ⎕←⍒'HelloWorld'

Dyalog APL

@HyperNeutrino
1 6 10 2 3 4 9 5 7 8
8 5 7 3 4 9 2 10 6 1

HyperNeutrino

⎕←⍋⌽'HelloWorld'

Dyalog APL

7:46 PM

@HyperNeutrino
10 5 1 9 2 7 8 4 6 3

Zacharý

⎕←{(⌽⍒⍵)=⍋⍵}'HelloWorld'

Dyalog APL

@Zacharý
1 1 1 1 0 1 0 0 0 1

Zacharý

⎕←{(⍒⌽⍵)=⍋⍵}'helloworld'

Dyalog APL

@Zacharý
0 0 0 0 0 0 0 0 0 0

Zacharý

⎕←{(⌽⍒⍵)=⍋⍵}'helloworld'

Dyalog APL

7:48 PM

@Zacharý
1 1 1 0 1 0 0 0 1 1

Adám

@Zacharý OK, can we move on?

Yes

Reverse compose ⍒=⍋

no

That was what I just was going testing, RosLuP

Adám

7:50 PM

OK, let's see if we can cover ⍳.

Monadic ⍳ is the index generator. ⍳a generates an array of shape a where the elements are the indices for that element:

⍞←⍳10

Dyalog APL

@Adám 1 2 3 4 5 6 7 8 9 10

Adám

⎕←⍳2 4

Dyalog APL

@Adám
┌───┬───┬───┬───┐
│1 1│1 2│1 3│1 4│
├───┼───┼───┼───┤
│2 1│2 2│2 3│2 4│
└───┴───┴───┴───┘

HyperNeutrino

⎕←⍳2 3 4

Dyalog APL

@HyperNeutrino
┌─────┬─────┬─────┬─────┐
│1 1 1│1 1 2│1 1 3│1 1 4│
├─────┼─────┼─────┼─────┤
│1 2 1│1 2 2│1 2 3│1 2 4│
├─────┼─────┼─────┼─────┤
│1 3 1│1 3 2│1 3 3│1 3 4│
└─────┴─────┴─────┴─────┘
┌─────┬─────┬─────┬─────┐
│2 1 1│2 1 2│2 1 3│2 1 4│
├─────┼─────┼─────┼─────┤
│2 2 1│2 2 2│2 2 3│2 2 4│
├─────┼─────┼─────┼─────┤
│2 3 1│2 3 2│2 3 3│2 3 4│
└─────┴─────┴─────┴─────┘

Zacharý

7:52 PM

⎕←⍴⍳2 3 4

Dyalog APL

@Zacharý
2 3 4

Erik the Outgolfer

yeah monadic ⍴∘⍳ is the same as monadic ⊢

Adám

Any bets on what ⍳0 gives?

Zacharý

⍬ ?

Erik the Outgolfer

yeah

HyperNeutrino

7:54 PM

i'm guessing that's empty list?

Adám

@Zacharý Yes. And what about ⍳0 0?

@HyperNeutrino Yes.

HyperNeutrino

ok

@Adám ⍬ as well?

Erik the Outgolfer

⎕←⍳0 0

dzaima

@Adám 0 0⍴⍬?

Dyalog APL

@EriktheOutgolfer

Rebuilding user command cache... done
Was OFF -trains=box -fns=off

Real time: 1.051 s
User time: 0.983 s
Sys. time: 0.036 s
CPU share: 97.05 %
Exit code: 0

Adám

7:55 PM

@HyperNeutrino Nope. remember that the result must have the same shape as the argument.

@dzaima Yes.

Zacharý

@EriktheOutgolfer What explains that then?

HyperNeutrino

hm

Erik the Outgolfer

@Adám doesn't seem like it

      0 0⍴⍬
┌⊖┐
⌽0│
└~┘
      ⍳0 0
┌⊖──────┐
⌽ ┌→──┐ │
│ │0 0│ │
│ └~──┘ │
└∊──────┘

Adám

@EriktheOutgolfer The reason for this strange result is that there is nothing to show, so the bot gives you the debug info instead.

Erik the Outgolfer

@Adám that's why RIDE is useful to have

Adám

7:56 PM

⎕←⍳0 0⊣⎕SE.UCMD'box on -s=max'

Dyalog APL

@Adám
┌⊖──────┐
⌽ ┌→──┐ │
│ │0 0│ │
│ └~──┘ │
└∊──────┘

Adám

@EriktheOutgolfer Uh, you shouldn't be programming using a chat bot. Yes, use the desktop version and either the terminal interface, RIDE or (on Windows) the IDE.

Erik the Outgolfer

@Adám I'll install IDE too, when I sometime boot into Windows :-P

Adám

@dzaima Oh, no it isn't 0 0⍴⍬ because each element must have two element (coordinates), and in 0 0⍴⍬ each element has only one.

Erik the Outgolfer

it's not a priority for me to request a new license for Windows currently

Zacharý

7:59 PM

0 0⍴(⍬ ⍬)?

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