The APL Orchard

Fmbalbuena

1:18 AM

@Adám Not interesed in judaism but i will learn APL.

not now.

PyGamer0

4:32 AM

@Fmbalbuena i think he does

Fmbalbuena

4:13 PM

website of @xpqz book?

xpqz

4:31 PM

xpqz.github.io/learnapl/intro.html

Jerome Ibanes

@Adám I'm going to try to attend tomorrow's meetup

Fmbalbuena

5:47 PM

@Adám are you active?

@Adám can you teach me a command in 15:00 UTC (if i can)

Adám

Announcement: APL ∊ BCN about to start on Zoom.

@Fmbalbuena Yes, now I am.

Fmbalbuena

> @Adám Not interesed in judaism but i will learn APL.

Do you understand ^?

Adám

Yes, I understand, but you asked me why I'd be gone, so I gave you the answer.

@JeromeIbanes That's now!

Jerome Ibanes

yup, please let me in

Adám

@Fmbalbuena The is the solution I was looking for.

Fmbalbuena

6:00 PM

⋄'aabbccde'{⍺~(⍺~⍵)}'abef'

TryAPL

@Fmbalbuena aabbe

Fmbalbuena

correct?

Adám

Yes. But can you see how you can shorten it a little?

Fmbalbuena

oh i found something wrong

⋄'aabbccde'{⍺~⍺~⍵}'abef'

TryAPL

@Fmbalbuena aabbe

Fmbalbuena

6:01 PM

1

Q: How to check if the string is reshaped in APL?

How to check if the string is reshaped? Example: "aab" returns 0 because "a" can't be reshaped to this string nor any other shorter string. Another example is "aabbaab" returns 1 because "aabb" can be reshaped to this string. A lot of examples can found this: Returns 1 101 abba abcab abacedabarab...

^ My first SO question about APL.

Adám

Congratulations. As (Kamila and) I said, that's a really interesting problem.

Fmbalbuena

3 users (Adám, Kamila and caird) said that is a really interesting problem.

ok so another task but first a command.

Adám

OK.

So let's learn dyadic ⍳

It takes a list on the left and either a single element or a list on the right.

Fmbalbuena

ok i have already learned monadic ⍳ but not dyadic ⍳

@Adám example?

Adám

For each element on the right, it returns the index of the first identical element in the list on the left: ⋄ 'hello'⍳'l'

TryAPL

6:07 PM

@Adám 3

⋄ 'helo'⍳'l'

@Fmbalbuena 3

⋄ 'hello'⍳'olle'

@Adám 5 3 3 2

⋄ ⍳⍨'hello'

6:08 PM

@Adám 1 2 3 3 5

Fmbalbuena

⋄ 'There is no plus sign'⍳'+'

@Fmbalbuena 22

Ah, great question!

Hmmm...

If it isn't there, it gives the first index beyond the end.

Fmbalbuena

6:09 PM

⋄ 'abc'⍳'+' ⋄ ⍴'abc'

TryAPL

@Fmbalbuena
4
3

Adám

This makes it easy to "translate": ⋄ 'ABCX'['abc'⍳'cat']

TryAPL

@Adám CAX

Fmbalbuena

Hmmm i haven't learned "[]" yet.

Adám

Yes you have. That's indexing.

Fmbalbuena

6:10 PM

⋄'abc'⍳'cat'

TryAPL

@Fmbalbuena 3 1 4

Adám

But maybe you didn't realise that you can use multiple indices inside the brackets.

a task?

Yes.

a task for me?

6:12 PM

Yes: Write a function that takes an element on the left, and a list on the right, and returns 1 if the element exists in the list, and 0 otherwise.

E.g. 'a' F 'abc' gives 1 and 'x' F 'abc' gives 0.

Fmbalbuena

6:23 PM

@Adám ^

done

Adám

@Fmbalbuena Remember that if not found, the result is one MORE than the length.

Fmbalbuena

⋄'x'{((⍴⍵)+1)≠⍵⍳⍺}'abcx'

Adám

⎕←'abc'⍳'x'

TryAPL

@Adám 4

@Fmbalbuena 1

Adám

@Fmbalbuena Now it will work with ≠

Fmbalbuena

6:26 PM

ok

learned; but i have to gtg now, but i still remember the dyadic "⍳", one more task for later?

Adám

You next task is to shorten it down by using a different relationship than ≠

Fmbalbuena

⋄'x'{(⍵⍳⍺)≠(⍴⍵)+1}'abcx'

TryAPL

@Fmbalbuena 1

Fmbalbuena

@Adám i can't but i have to gtg now.

Adám

Try when you have time.

Jerome Ibanes

8:43 PM

@Adám I'm going to try to share a folder now

okay lmk if it worked when you're awake please, I'll add more stuff later.

you'll find a png in there to see a working session

I can help you set it up

Adám

Got it. I'll try it out and let you know.

Jerome Ibanes

9:12 PM

added a howto.txt

Adám

That'll come in handy.

Jerome Ibanes

there are two, one of them is to setup utf-8 support

the other one to just install it

lmk if you run into issues

Adám

I will.

Fmbalbuena

9:46 PM

@Adám i'm thinking about COW (Code of the Week)

can i put to apl.wiki?

Adám

What is that?

Fmbalbuena

> you need to sleep. i'm adding "my code of the week" in my about tomorrow.

Adám

OK, thanks for your concern for me!

Fmbalbuena

Then i should put to "Code of the week" or "Fmbalbuena/Code of the week"?

in apl.wiki

Adám

@Fmbalbuena I don't know yet what it is, but put in under your user name for now. It can always be moved later if necessary.

Fmbalbuena

9:51 PM

under your user name?

Adám

"Fmbalbuena/Code of the week"

Fmbalbuena

ok

oops i typed "ap" and i got "apl.chat", not "apl.wiki"

@Adám how to change the default keyboard, the default keyboard is APL keyboard.

Adám

WindowsKey+Space

Fmbalbuena

@Adám I'm thinking for checking if the number is square.

⋄{⍵=⍵×⍴⍵}9

TryAPL

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

Fmbalbuena

10:00 PM

Is there problems?

Adám

What problems?

Fmbalbuena

⋄{⍵=⍵×⍴⍵}9

TryAPL

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

Adám

@Fmbalbuena You already know enough to check if a number is square.

Fmbalbuena

@TryAPL Why?

Adám

10:02 PM

Because ⍴9 is ⍬ and 9×⍬ is ⍬ and 9=⍬ is ⍬

Fmbalbuena

oh i used "⍴" instead of "⍳"

Adám

:-)

Fmbalbuena

⋄{⍵=⍵×⍳⍵}9

TryAPL

@Fmbalbuena 1 0 0 0 0 0 0 0 0

Fmbalbuena

i forgot to put something

⋄{+⌿⍵=⍵×⍳⍵}9

TryAPL

10:03 PM

@Fmbalbuena 1

⋄{+⌿⍵=⍵×⍳⍵}8

@Fmbalbuena 1

incorrect...

⍵=⍵×⍳⍵ is always 1 followed by ⍵-1 zeros.

Fmbalbuena

⋄9×⍳9

TryAPL

10:04 PM

@Fmbalbuena 9 18 27 36 45 54 63 72 81

Fmbalbuena

⋄(⍳9)*2

TryAPL

@Fmbalbuena 1 4 9 16 25 36 49 64 81

Adám

Very good. You're getting there.

Fmbalbuena

⋄{+⌿⍵=(⍳⍵)*2}9

TryAPL

@Fmbalbuena 1

Fmbalbuena

10:06 PM

⋄{+⌿⍵=(⍳⍵)*2}⍳4

TryAPL

@Fmbalbuena (1 trailing line)
RANK ERROR
      {+⌿⍵=(⍳⍵)*2}⍳4

␄

Adám

This doesn't work because it'd include ⍳⍳n

Fmbalbuena

List not working

⋄{+⌿⍵=(⍳⍵)*2}⍳2

TryAPL

@Fmbalbuena (1 trailing line)
RANK ERROR
      {+⌿⍵=(⍳⍵)*2}⍳2

␄

Fmbalbuena

⋄⍳⍳2

TryAPL

10:07 PM

@Fmbalbuena
┌───┬───┐
│1 1│1 2│
└───┴───┘

Adám

There's a better way to check if a number is square.

Fmbalbuena

@Adám yeah, but which?

Adám

Let me give you a couple of small problems.

Define a squareroot function.

Fmbalbuena

@Adám ok

you are slow at writing tasks.

Adám

I'm sorry.

Fmbalbuena

10:09 PM

nvm

Adám

Your squareroot function should be such that F 4 gives 2 and F 0.25 gives 0.5

The other problem is to define a function that checks if the argument is an integer. F 10 should give 1 and F 10.1 should give 0

Fmbalbuena

⋄{⍵*0.5}16

TryAPL

@Fmbalbuena 4

Adám

Very good. That solves the first problem.

The second one is a bit trickier, but you can do it!

Fmbalbuena

⋄{(1+⍴⍕⍵)≠(⍕⍵)⍳'.'}100.4

TryAPL

10:13 PM

@Fmbalbuena 1

Fmbalbuena

hmm

Adám

Try to do it using mathematics.

⋄{⍵=1|⍵}100.4

@Fmbalbuena 0

⋄{⍵=1|⍵}100

10:14 PM

Ah, you're getting there!

@Fmbalbuena 0

⋄1|100

@Fmbalbuena 0

wait what?

Division remainder when 100 is divided by 1

Fmbalbuena

10:16 PM

⋄{0=1|⍵}100

@Fmbalbuena 1

⋄{0=1|⍵}100.4

@Fmbalbuena 0

Very good. You solved it!

Fmbalbuena

⋄{0=1|⍵*0.5}⍳100

Adám

10:17 PM

@user1118720 Hi Richard. If you want to participate here, please email access@apl.chat

TryAPL

@Fmbalbuena

1 0 0 1 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1

Adám

And now you solved your original problem. I'm very proud of you!

@Fmbalbuena Can I add this to APLcart?

Fmbalbuena

aplwiki.com/wiki/User:Fmbalbuena/Code_of_the_Week

@Adám Yes

Adám

@Fmbalbuena Yeah, that's good.

@hyper-neutrino Can you give chat.stackexchange.com/users/534674/user1118720 access?

hyper-neutrino

@Adám done

user1118720

10:24 PM

:) Thanks.
Should I give an introduction?

Adám

You're certainly welcome to, but not obligated to.

Also, since you're new to Stack Exchange chat, I highly recommend having a look at apl.wiki/APL_Orchard#Features

@hyper-neutrino That was incredibly quick. Thanks.

Fmbalbuena

@Adám Added?

Adám

Not yet, working on it.

Fmbalbuena

Quiz difficulty: Easy

user1118720

I just started discovering APL. I am not a (profesional) programmer but very interested in mathematical problems. I do have some experience with C and some other languages. But I am mostly attracked by the different view APL gives on solving problems.

I read some of the APL manuals this week and started looking at the Advent of Code 2021. also watched some YouTube videos. Some are to basic and some are to advanced. Best thing to do now is starting solving some problems I think.

I installed Dyalog and RIDE. RIDE is not working however. Have to figure that out. But Dyalog is working fine.

Thanks for letting me join

Fmbalbuena

10:34 PM

@Richard do you know the division in APL?

Adám

@Richard apl.wiki/Learning_resources might be useful and apl.wiki/Advent_of_Code might interest you. I can recommend problems.tryapl.org for simple problems to drill yourself on. We should get your RIDE problem fixed. What OS are you on?

Richard

Yes. I do know al the basics and the most common functions and operands. (think have to install the APL font to enter it in the chat.

Fmbalbuena

@Adám when you add the square checking?

Richard

RIDE is installed on Windows 8

Adám

@Richard The font isn't essential for using chat (in fact, it won't help).

@Richard If you're on Windows, you don't need RIDE at all. IMHO the default Windows IDE is better, even if it looks dated.

Richard

10:37 PM

ah, ok :)

Adám

@Fmbalbuena aplcart.info?q=square%20numbers

Fmbalbuena

I'm asking: what is "∘"?

Richard

Jot. Inner product?

Adám

Here, it "curries" or binds an argument to a dyadic function, giving a monadic function.

Fmbalbuena

@Adám what does even mean?

Adám

10:39 PM

So +∘1 is an increment function and -∘1 is a decrement function.

∘ is a dyadic operator, but you've not learned any dyadic operators yet.

Fmbalbuena

⋄-∘1

TryAPL

@Fmbalbuena
 ∘
┌┴┐
- 1

Adám

Dyadic operators are similar monadic operator like ⌿ and ⍨ which you've learned, but they take two things (one on each side) to produce a new function.

⎕←(-∘1) 42

TryAPL

@Adám 41

Adám

⋄ Square←*∘2 ⋄ Square ⍳5

TryAPL

10:42 PM

@Adám 1 4 9 16 25

Richard

+ is dyadic and Jot making it monadic binded with 1?

Adám

Correct.

Richard

Cool

Adám

You can also bind to either side: ⋄ Double←2∘× ⋄ Double ⍳5

TryAPL

@Adám 2 4 6 8 10

Richard

10:47 PM

Thanks, couldn't follow the explenation in the manuals.

When do yo use it?

in dfns or with tacit programming?

(last one still quite complicated for me)

Adám

You could use it almost anywhere. But these are examples of tacit programming, because the function never mentions its argument explicitly. The equivalent non-tacit functions would be {⍵-1} and {2×⍵} etc.

Tacit doesn't have to be complicated.

You can make any code unreadable, tacit or not!

Richard

:)

Started APL last week and watched some tacit examples yesterdayin some youTube videos. So I should be patient. I'm getting addicted...

Adám

@Richard Are you aware of apl.wiki/Tacit_programming?

Richard

Yes,. forks and ATOP are ok, but got little bit lost on 4 and 5 trains. ]boxing -trains=tree helps a lot

Adám

You do realise that a 4-train is simply an atop where the right side is a fork, right? And a 5-train is just a fork where the right side is itself a fork.

Richard

10:59 PM

This one also gives some help:
https://xpqz.github.io/learnapl/tacit.html

Yes I do. But still find it difficult to interpret and construct. But I just should practice

Adám

@Richard Thanks. I'll add that to the APL Wiki article.

Richard

Also did this course but the last few chapters.
I think it;s a little bit out dated but has a good pace for someone new to APL.

Adám

Which course?

Richard

tutorial.dyalog.com

Adám

Ah yes. Someone is currently working on updating that.

Richard

11:05 PM

Some of the problems I could not reproduce until I found out I had to change the IBM compatebility

Adám

Yeah.

Richard

https://problems.tryapl.org/ is nice, thanks!
But I''l install the alternative APL keyboard. The CTRL keys are not working outside Dyalog.
Thanks for helping us out!!

Adám

@Richard I personally use the AltGr keyboards from here

Richard

11:22 PM

Thanks, just installed. Probably have to restart the computer cause it's not working yet

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