CMQ: What would you like to see presentations about at Dyalog '21?

@Adám the graphics facilities you showed me last time.

@EliasMårtenson Which ones was that? Bitmap rendering?

oh does that require foreign libraries?

Well, pretty much nothing requires libraries, as you can write it yourself, but many things sure are easier with pre-written code :-)

not yet ready for writing Huffman encoding :D

@Adám Yeah, the ones that you used to get pretty fast bitmap animations.

@EliasMårtenson Might be well suited for a webinar.

Has anyone done a border detection algorithm in APL?

I'd like to find polygons in a grid

For bitmaps?

 bound←{(⊢∧9≠{+/,⍵}⌺3 3)⍵}

yeah but it's a bit more complex

do you have some example images?

=====
[   ]
 [ ]
 ===

so horizontal lines and vertical lines have separate chars

and it needs to validate the lines as well

and what is intended output for this charmap?

should be the coordinates of the corner points

I'll be trying to do it sometime soon

it's for an esoteric language

the thing is that there will be multiple of these

so i'll need each boarder as a separate group of pts

I think you should define some properties of the polygons: are the coordinates of vertices limited to integers or are fractions allowed? How about the slope of a side? Slope of something like 7/3 would result in a line having block sizes of 2, 3, 2 or something similar and make it hard to decide whether the side has more vertices on it or not

Also, what is the smallest size of a valid polygon?

3x3

aka

[ ]

Lol, the three equal signs being message separator

wait, let me just link the spec

esolangs.org/wiki/zirconium

@Bubbler Wait, really? I found an old meta post about hidden features saying it was --- but neither that, nor === seems to have an effect.

@LdBeth This one begs to be a train: bound←⊢∧9≠{+/,⍵}⌺3 3

@Adám See Razetime's messages above, between "aka" and "===". That's what a message separator does in SE chat

Oh, both --- and === work, but it is kind of ugly as the separator is visible.

CMC: Golf {(⍴⍵)⍴⍬⍴0⍴⍵}

@Adám ⍴⍴⍬⍴0∘⍴ :P

I have 4.

If I'm allowed ⎕ML←0, isn't it just ∊?

No it isn't.

oh

oh yeah, mixing types doesn't work

it's the entire array replaces with fill values

yep, I'm pretty stumped

@Adám what does this CMC means?

@WongJiaHau Chat Mini Challenge.

is it ⍬↑⍨⍴?

no (doesn't work on strings)

@Adám sorry I mean what does Golf means?

oh it doesn't

@WongJiaHau make the code shorter

I see, as long as it works the same right?

yep

Does ⍴↑⍴↓⊢ work?

@Bubbler I think that will work.

what about 2⊃2↑⊂

Why 2?

it's one thing after ⊂, taking 2 makes a fill copy

I don't know what the task is honestly, i'm doing "entire array replaced with fill values"

i don't know how that works for mixed type

if it's a hint i didn't get it :)

I'm asking for replacing all elements with the fill value for the first element.

i see

⎕←(2⍴1) (2⍴3){⎕IO←0⋄∧/≠⌿2↑⍉⌊.5×⍋⍤1⊢⍉↑⍺,⍵}(2⍴4) (2⍴7)

@xpqz 0

@xpqz No need for the ⊢ there.

(Also no idea what this is.)

Solution for problems.tryapl.org/psets/…

I just got bitten by the ⎕IO.

@Razetime I'll let someone else more experienced answer, but from my 5 second glance it looks a bit like VerifyKey is a match ≡ along with dfns.dec (or dfns.hex) and ⎕UCS

@RikedyP What are you responding to?

@Adám An email, sorry should have clarified. I meant to write "someone else more experienced answer your email, but..."

@RikedyP cool, will see it

CMQ: Recording the next Array Cast with Eric Iverson as guest. Any questions I should ask him?

What does he think about index origin?

@LdBeth I'll try to ask.

(not related) when you do 'IÏ'⎕CY'isolate' and try to use it, you get a cryptic 'value error' with no more information, it seems you need to load the entire thing, if this could be fixed it would be nice, otherwise is it possible to make the error a bit better?

also, not that I can do it now I have to load the entire thing, but is there a way to import one thing and rename it? like from whatever import thing as name in python

ok, now instead of value error I get ⍎VALUE ERROR, why on earth f¨x should be any different to f IÏ x I don't know, but clearly it is

the way isolate works is it just copies the operand & argument over to the new process, but that may not include things they implicitly refer to

oh, looks like the fix is to spam ## everywhere or something

ISOLATE: Callback server restarted or not

@alwalo This question is addressed by Eric Iverson in the next episode of ArrayCast.com (due to be released on Saturday).

Very cool Adam I wonder what he will say

Building the suspense…

when are you recording it in case I think of any questions?

@rak1507 When I wrote that CMQ. Sorry, didn't think to ask here earlier. Too busy teaching lately.

Oh, no problem

He would be a good guest for the campfire

@rak1507 Ah, very good point. I'll get in contact with him. Thanks!