The APL Orchard

Fmbalbuena

00:05

@Adám but i'm using power.

Adám

@Fmbalbuena Yeah, so?

Fmbalbuena

@Adám ⋄Fac←{×⌿⍵}⋄Fac 1⋄Fac 7

TryAPL

@Fmbalbuena
1
7

Fmbalbuena

(not working when the parameter is 0)

Adám

You're missing one thing here.

@Fmbalbuena Try reading your code and you'll see what's missing.

Fmbalbuena

00:08

oh

⋄Fac←{×⌿⍳⍵}⋄Fac 1⋄Fac 7

TryAPL

@Fmbalbuena
1
5040

Fmbalbuena

Done

⋄Fac←{×⌿⍳⍵}⋄Fac 1⋄Fac 0

TryAPL

@Fmbalbuena
1
1

Fmbalbuena

why returns 1, @Adám?

Adám

@Fmbalbuena A. Because that's the correct answer for the factorial of 0, and B. because that's the identity element for multiplication.

@Fmbalbuena This solution is perfect

Fmbalbuena

00:10

⎕←⍳0

TryAPL

@Fmbalbuena Response looks like a 1-by-0 matrix.

Adám

⍳0 is the list of the first 0 integers.

Same as 0⍴0

Fmbalbuena

⎕←*⌿0⍴0 0

TryAPL

@Fmbalbuena 1

Fmbalbuena

but whyyyy?

Adám

00:12

Because x¹=x for all x

So too ×/0⍴0 gives 1 because 1×x=x for all x.

And +/0⍴0 gives 0 because 0+x=x for all x.

-/0⍴0 and ÷/0⍴0 give 0 and 1 because x-0=x and 0÷1=x for all x.

Fmbalbuena

⋄FNC←{⍺+⍵*2}⋄FNC⌿1 2 3 4 5

TryAPL

@Fmbalbuena 5.074254262E11

Fmbalbuena

@Adám Can you teach one more command?

Adám

I'll teach you TWO for the price of one!

Fmbalbuena

@Adám ?

Adám

00:16

Dyadic ⌈ is the maximum of its arguments: ⋄ 3⌈4 ⋄ 5⌈5 ⋄ ¯3⌈¯1

TryAPL

@Adám
4
5
¯1

Fmbalbuena

that's easy to learn

Adám

Can you guess the symbol for the dyadic minimum function?

Fmbalbuena

⌊

Adám

You got it!

So I taught you one and you learned TWO!

Fmbalbuena

00:17

⋄ 4⌈⌊5 Errors?

TryAPL

@Fmbalbuena 5

Adám

No, but monadic ⌊ means something else.

It means "floor" or "round down".

Can you guess the symbol for "ceiling" or "round up"?

Fmbalbuena

I forgot what is monad and others.

@Adám ⌈

Adám

@Fmbalbuena Indeed. I did it again, didn't I?

@Fmbalbuena Dyadic=2 arguments. Monadic=1 argument.

Fmbalbuena

@Adám others?

Adám

00:19

Niladic=0 arguments.

Fmbalbuena

one more?

Adám

Nope.

Do you want a task?

Fmbalbuena

@Adám yep

Adám

Given a list of numbers, find the largest element. E.g. Max 3 1 4 1 5 9 2 should give 9.

Fmbalbuena

@Adám f←{⌈⌿⍵}

Adám

00:22

Amazing! One more task?

Fmbalbuena

@Adám yes but a bit harder.

Adám

OK, given a list of numbers, find its range, i.e. the difference between the largest and the smallest element. E.g. Range 3 1 4 1 5 9 2 should give 8 and Range 42 42 42 should give 0.

Fmbalbuena

i can't solve with one tradfn.

Adám

You can easily solve it with a single dfn (=lambda).

Fmbalbuena

@Adám wdym?

Adám

00:26

I'm telling you that you have all the info and skills to solve this task using a single lambda.

I can give you some hints if you need it.

Fmbalbuena

a hint?

Adám

You already solved the problem of finding the maximum of a list. Try finding out how to get the minimum, and then subtracting those two formulas.

Fmbalbuena

@Adám f←{⌈⌿⍵-⌊⌿⍵}

Adám

Good.

This gives the right result, but for the wrong reason. Can you see why?

Do you want a hint?

Fmbalbuena

yes

Adám

00:34

Every APL function takes as right argument, everything to its right.

Fmbalbuena

no idea what testcase is but... f←{(⌈⌿⍵)-⌊⌿⍵}

Adám

Yes, now you nailed it! Well spotted.

Fmbalbuena

testcase?

Adám

There are no test cases for which your previous solution would fail.

Fmbalbuena

what array will fail this function?

Adám

00:37

None.

Fmbalbuena

but why this is incorrect?

Adám

I didn't say it was. I said your original solution gives the right result.

Fmbalbuena

ok. wait...

Adám

But the problem was that you were subtracting the minimum from the entire array, instead of subtracting it from the maximum.

Fmbalbuena

wait... i found something weird.

Adám

00:39

Sure?

Fmbalbuena

⍝ seems sus.

Adám

Heh. It is the comment symbol.

It looks like a little lamp or LED to enlighten you.

Fmbalbuena

difference between = and ≡?

Adám

= maps over elements like + and × while ≡ compares entire arrays: ⋄ 1 2 3=1 4 3 ⋄ 1 2 3≡1 4 3 ⋄ 1 2 3≡1 2 3

TryAPL

@Adám
1 0 1
0
1

Adám

00:44

Similarly for ≠ vs ≢

Fmbalbuena

⍎ or ⍕ converts int to str?

Adám

Not exactly. ⍎ executes a string as APL code, while ⍕ formats any array as a character array.

Fmbalbuena

what command converts int to str?

Adám

⍕ will do that, as an int is an array, and a str is a character array.

⋄ '12' ≡ ⍕12

TryAPL

@Adám 1

Fmbalbuena

00:47

⍕ or ⍕?

Adám

What?

Fmbalbuena

⍕ formats any array as a character array. ⍕ will do that, as an int is an array, and a str is a character array.

Adám

I don't understand what you're asking.

Fmbalbuena

⋄⍕12

TryAPL

@Fmbalbuena 12

Fmbalbuena

00:49

i don't understand

Adám

Note that the default display form for 12 and '12' are identical.

Bubbler

@Fmbalbuena You just entered the same character twice

Adám

Here, consider this: ⋄ 4⍴12 ⋄ 4⍴⍕12

TryAPL

@Adám
12 12 12 12
1212

Adám

@Fmbalbuena You understand ^?

Fmbalbuena

00:52

@Adám but the difference is ⎕←(12,6)≡'12','6'⋄⎕←12,5

TryAPL

@Fmbalbuena
0
12 5

Fmbalbuena

@Adám yep

Adám

OK, good.

Fmbalbuena

xpqz's book?

Adám

Is highly recommended.

Fmbalbuena

00:54

do you have xpqz's book?

Adám

You mean a link to it?

Fmbalbuena

@Adám or picture.

Adám

It doesn't really exist in physical form unless you print the PDF. You can find a link to it in this room's starred messages or at apl.wiki/Learning_resources#For_programmers_unfamiliar_with_APL.

Fmbalbuena

@Adám can you teach me Making AI (for some game boards) in APL whin i learn a lot of APL?

Adám

@Fmbalbuena Maybe, but let's see once you've learned a lot more APL.

Fmbalbuena

00:59

@Adám I forgot which link generates random problems.

Adám

You can always find it by going to aplcart.info and clicking Quiz at the bottom.

Fmbalbuena

monad is 2 args?

Adám

No, 1. You can maybe remember it like a monologue is one person speaking while a dialogue is a conversation between two people.

MONO=1, DIA=2.

MONadic vs DYAdic.

Fmbalbuena

Niladic?

Adám

0, like nil=nothing or nul(l).

Fmbalbuena

01:07

@Adám one task?

Adám

You want another task from me?

Fmbalbuena

Yes

Adám

OK, I'll give you one that is a little tricky. Given a list of numbers, count how many are greater than 3.

E.g. 3 1 4 1 5 should give 2 (namely 4 and 5).

Fmbalbuena

Remember, sum is +⌿

Adám

Yes.

Fmbalbuena

01:10

@Adám f←{+⌿2≠⍵⌈2}

Adám

That's pretty clever, but it fails on 2.5 1 4 1 5

Let me know if you need a hint.

Fmbalbuena

@Adám ⋄f←{+⌿3≠⍵⌊3}⋄f 3 2 1 not working.

TryAPL

@Fmbalbuena 2

Fmbalbuena

hmm... i found.

Adám

You need to use a function I've not taught you, but you should be able to guess.

Fmbalbuena

01:14

change "≠" to "=", correct?

Adám

No.

Fmbalbuena

@Adám f←{+⌿3=⍵⌊3}

Adám

Ooh, nice, that actually works.

Bubbler

That's "greater than or equal to 3", not "greater than 3"

Adám

However, there's a much better way.

@Bubbler Oh, you're right.

Fmbalbuena

01:17

oh sorry

@Adám f←{+⌿⍵>3}

Adám

@Fmbalbuena That's what I wanted to see! ♥

Fmbalbuena

@Adám i like one more task because APL fun.

Adám

OK, given a list of numbers, answer 1 if all are greater than 3 but 0 otherwise. E.g. 3 1 4 1 5 should give 0 while 31 41 5 should give 1.

Fmbalbuena

@Adám f←{×⌿⍵>3}

Adám

Amazing. You're really picking this up very well.

Fmbalbuena

01:23

but is there shorter way to do "AND" in APL?

Adám

There's a separate symbol for AND (∧) but it is dyadic, so you still would need ⌿

Fmbalbuena

ok i learned 3 commands. Can you remember the commands that i learned?

Adám

More or less.

Fmbalbuena

@Adám but why?

Adám

Because my memory isn't perfect.

Fmbalbuena

01:27

@Adám but nevermind i will ask commands that i remembered.

xpqz

08:48

Any idea what would stop me from creating a workspace? I get the following error:

)save myws
Can't save - file could not be created.

Adám

./myws could be write-protected or a directory.

Or open somewhere else.

xpqz

Hmm, that doesn't seem to be it. C;losed the interpreter and tried again:

)save definitelynewfile
Can't save - file could not be created.

Adám

Do you have write access to the current dir?

xpqz

      ]FILE.CD
/

Ok, in my humble opinion, that's a mental default :)

Adám

I don't know why that would be the default startup dir, but I'll log an issue.

xpqz

08:53

I swear it used to default to the user's homedir. I've installed, uninstalled, and re-installed various beta versions recently, not sure if that could be the cause.

Adám

Do you want to investigate a bit before I log?

xpqz

I've noticed is that Dyalog's recommended uninstall mechanism (drag the folder into the trash) probably isn't sufficient/correct from 18.1 and onwards -- if I have 18.1 and then install 18.2, followed by uninstalling 18.2, all the dyalogscript stuff is gone, and no longer works in 18.1.

This to me suggests it won't be possible to run multiple versions of dyalog moving forward.

I wonder if the default directory is a symptom of the same thing.

Adám

Can you describe the whole thing to [email protected]?

xpqz

Sure.

Aha - it leaves a hanging symlink.

(py39) Stefans-MacBook-Pro:d stefan$ file /usr/local/bin/dyalogscript
/usr/local/bin/dyalogscript: broken symbolic link to /Applications/Dyalog-18.2.app/Contents/Resources/dyalog/Samples/scripts/bin/dyalogscript

I can fix that manually for sure.

It also leaves a broken link /usr/local/bin/dyalogscript.bash

Resetting those two manually fixes it.

RikedyP

10:43

@Adám DOMAIN ERROR - or with quotes, NONCE ERROR

Adám

@RikedyP Well, then you've got issues to log.

RikedyP

@Adám Oh seems to be when trying to copy HttpCommand (which I should probably keep at root level rather than within kit)

before I log issue, can you think of any reason why ⎕NS shouldn't copy httpcommand class?

Adám

No.

RikedyP

ty

Adám

@PyGamer0 I just realised that |∘| and |⍤| and ⌊○⌊ are all valid APL functions.

PyGamer0

10:48

@Adám wait, what (the first two are composed right?)

what about the last one?

Adám

Yeah, the first is equivalent to {⍺←⊢ ⋄ ⍺||⍵} and the second to {⍺←⊢ ⋄ |⍺|⍵} and the third to {⍺←⊢ ⋄ (⍺⌊⍵)○(⍺⌊⍵)}.

@RikedyP Assign to Geoff and maybe mark as related to the ref-as-left-arg issue.

← 4 messages moved from The Nineteenth Byte

RikedyP

@Adám Well I tried to do it fresh and couldn't repro outside of my aoc project

Adám

:-/

PyGamer0

11:05

how were the APL glyphs chosen?

Adám

@PyGamer0 Many were based on TMN or derived from it. Iverson seems to have come up with some, and some where chosen by Quaker consensus when Iverson's notation was linearised into what became APL. Newer symbols were chosen with or without consensus by various vendors.

PyGamer0

11:30

how do i map a char vector to numbers, say 'ABCD' to 1 2 3 4 so 'ABBCCDDCAC' becomes 1 2 2 3 3 4 4 3 1 3

Razetime

⋄ ⎕A⍳'ABCD'

TryAPL

@Razetime Did you forget to add backticks around your code (`⋄ code`)? You can edit your message and I will edit my reply.

Razetime

      ⋄ ⎕A⍳'ABCD'
1 2 3 4

TryAPL

@Razetime 1 2 3 4

xpqz

12:38

If you did today's AoC without help from dfns, you're a hero.

Fmbalbuena

12:51

@xpqz what is dfns?

dzaima

@Fmbalbuena dfns.dyalog.com/n_contents.htm

Fmbalbuena

@dzaima TLDR

dzaima

@Fmbalbuena a namespace of various useful functions

Adám

@Fmbalbuena apl.wiki/Dfns_workspace

Fmbalbuena

ok.

xpqz

13:14

Day 15: gist.github.com/xpqz/75a25a23365da82448cbbe47ce46c1c4

RGS

@xpqz Is it that difficult to implement a graph search algorithm..?

(SPOILER, dont' read this message if you want to solve day 15 all by yourself)
Not sure if you used a super-duper specialised version of something, but Dijkstra's algorithm shouldn't be _that_ hard to implement, right..?

xpqz

I've made a few over the years (A*, bfs, dijkstra) in APL. Never pretty.

RGS

Right.

xpqz

@RGS A*: gist.github.com/xpqz/0d1130082073c0d79378e33e6fe3c6ac

PyGamer0

@Adám i want to solve a problem

xpqz

13:19

but then you also need my heapq and dict implementations....

Adám

@PyGamer0 Any particular one?

PyGamer0

@Adám no, just a simple CMC

Adám

@PyGamer0 Have you looked at problems.tryapl.org?

PyGamer0

yes

Adám

And?

PyGamer0

13:22

i solved one problem

Adám

Is there a reason not to continue with those? They are all simple.

PyGamer0

ok

dzaima

@xpqz how fast is it?

Adám

@PyGamer0 You can still ask for feedback on your solutions to those problems here.

PyGamer0

@Adám ok

xpqz

13:24

@dzaima Passably. Around 30s on my 2016 i5:

]runtime "day15 d2"

* Benchmarking "day15 d2"
              (ms)
 CPU (avg):  30768
 Elapsed:    31793

dzaima

@xpqz ah. So not competing with my 0.4s in BQN :)

RGS

@dzaima damn

xpqz

Wait. wat?

RGS

@xpqz thanks

xpqz

Is there a trick shot here?

PyGamer0

13:26

how does this look? 2021 P1: {len←≢⍵⋄count←+/⍵∊'CG'⋄100×count÷len}

dzaima

@xpqz no. Just a regular dijkstra/breath first search, just without any ¨iness, and all long array operations. code

Adám

@PyGamer0 That's fine, although I really don't think the len variable adds any clarity.

dzaima

(my initial solution was 50 seconds though)

xpqz

@dzaima I bow to your superior cerebral fitness. I should really study bqn at some stage.

dzaima

it should port to APL just fine (and be many times faster in Dyalog, because nearly everything used in my solution isn't yet vectorized in CBQN)

RGS

13:33

@dzaima Does that mean you are going to port it? (☞ﾟヮﾟ)☞

dzaima

ugh fine

RGS

😆

You can't come in here flexing, and expect people to not want to learn something new.

dzaima

true

xpqz

@dzaima interesting -- all the time is taken by the wpath function -- curious that something that established would have its arse kicked so comprehensively.

PyGamer0

@Adám 2021 P2: {l←1+≢⍺⋄i×l>i←⍺⍳⍵}

xpqz

13:38

Hmm, it goes via the full spanning tree. That would be why.

Adám

@PyGamer0 That's fine, although can you think of a way to get rid of 1+ (which then also means that the variable l is a but unnecessary)?

PyGamer0

@Adám {i×(≢⍺)≥i←⍺⍳⍵}?

Adám

Very nice.

PyGamer0

ok how do i make that into a tacit function?

Adám

⍳(⊣×≤∘≢)⊣

This isn't a 1:1 translation.

PyGamer0

13:45

ok

why cant i turn boxing on with options on TryAPL

Adám

Because it is always on.

PyGamer0

@Adám but i want to change it to display trains=parens

Adám

You can't, sorry.

Use an installed system, e.g. TIO.

PyGamer0

but i dont have a language bar there(on android)

Adám

Even using my bookmarklet?

PyGamer0

13:52

@Adám wait let me try that

dzaima

here ya go:
https://dzaima.github.io/paste/#0jVIxS8NQEN7zK24zJdWXBxYUFFxEXHRxK06vDoHXUEwkQ8yiUNrgK4oUV6mDpQgO1UVwqf/kfonfe0lL3YTwuPvuu7vv7sKj8fEp9@9DT@Pl/sP2ziabKY/GVypZTLm8hXlydHi2IVtbUbwhPa0po0SRok50mRCyiM3b@udFcZS6QO4RZVxOHGk4YfMJQOsaaVZ@qqmOaw03UXU4PAhhkS@DVDfQ44Nk@PMUCMdakiRl8KySZdHFlHI/1WxmmENy/xFdGhWweF/zmyH99UEPaQkUGDJDTzbzVHuF53lJetFbDVVZiWqrc3hxpwogEUABBVaQDThca6AUkF3mXSkoRx6ojhh3QOs6WrzXc@O3uwJ0i3RFvDYqD2a2RBMFfGQMXsl3O2vw8NlKFnhWJZXV7O6gnXI2L3m4727wVSCKq7oW0on6TlTNlsHuNdZSiTUz0RQ@lzfYv0NQPRD4K8y8Ra3/1f0F#APL

3

RGS

@dzaima Thanks! Is it fast? :P

xpqz

How fast is it?

RGS

Wait, I thought you said it didn't use ¨? :P

dzaima

@RGS not using ¨ is very different from not using ¨y things

@xpqz 130ms

the three ¨es in step are all on 4-item arrays

RGS

13:59

Now I'll study your code :D Thanks for sharing!

dzaima

@dzaima 95ms if the file reading is extracted out and ⎕←s removed

PyGamer0

@Adám it working manually, when i paste the js

in the url bar

Adám

But not as a bookmark?

@Razetime Maybe you could amend APLgolf to (optionally) show a language bar?

PyGamer0

@Adám no the bookmark doesnt work, i cant click on it

Adám

:-(

PyGamer0

14:07

@Adám that would also be a good option

RikedyP

@dzaima +←1 thanks for sharing this!

xpqz

@dzaima Impressive indeed.

xpqz

14:54

@dzaima would you mind outlining what the five global state variables represent? (ll w sc c dirs)

RGS

I'll guess that dirs gives some “directions”. Maybe the costs of the 4 neighbours of each position, or something like that.

dzaima

15:05

@xpqz ll - flat vector of the costs; dirs - lists represending all neighbord for each item in ll; w - width (also height); sc - current "score" of a cell; c - the list of indices that need to be updated in the next step

in step, p - previous score for each current cell; nd - neighbor indexes; n new score for the cell; m - mask of improved scores

xpqz

Thank you.

dzaima

(sc has a ≢llth element that's always the maximum value, and dirs references that for the things that'd otherwise go out-of-bounds)

Razetime

@Adám yeah i can, the lb bookmarklet doesn't really change the functionality so it should be simple

Razetime

15:30

@Adám added

Adám

@Razetime How to activate?

xpqz

@dzaima That's cool. Best dijkstra I've seen in apl.

Fmbalbuena

16:46

@Adám i want to learn a command.

Adám

16:59

@Fmbalbuena Monadic ⌽ reverses its argument. E.g. ⎕←⌽'Hello'

TryAPL

@Adám olleH

Transcript for