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4:38 AM
@Adám this is for spheres
 
4:48 AM
@Adám by finger count, new solution is around 5 seconds, and old solution around 18
The indmin function isn't returning the results I want, as I want to return specific colors base on what was hit, though that's probably already solved I just need to map the results some new way
 
5:13 AM
actually, much easier than I thoughtcolors[(Pcs Scs 0)[l]]
 
 
1 hour later…
ngn
6:27 AM
@arcfide what do you think of ,\0 1 2?
 
6:51 AM
@ngn how do you drop a dimension?
I have a shape 1 2 8 6 and I want to drop the 1
so that I have a shape 2 8 6
 
ngn
@nathanrogers reduction deletes a dimension. you could do ⊢⌿ for instance
 
@ngn i have a 2 8 6 and an 8 6
I would like to make a 3 8 6
 
ngn
@nathanrogers ⍺⍪↑,⊂⍵ ⍝ there may be a better way
 
7:20 AM
@nathanrogers A286⍪A86
 
when I have an 8 6 and an 8 6 it doesn't work
it creates a 16 6
 
@nathanrogers True, but that wasn't your question.
 
ok, how do I extend joining 2 8x6 matrices such that I wind up with an additional leading dimension?
8x6 and 8x6 makes 2 8 6, a 2 8 6 and 2 8 6 makes 4 8 6
 
@nathanrogers For that you need a,[¯0.5]b or ↑a b
@nathanrogers Those two operations are fundamentally different, as the first adds an axis, the second not.
@nathanrogers If you want a general solution (specific, actually) that handles both rank-2 and rank-3 args, use {(⍺⍴⍨¯3↑1,⍴⍺)⍪(⍵⍴⍨¯3↑1,⍴⍵)}
{⍵⍴⍨¯3↑1,⍴⍵}{(⍺⍺ ⍺)⍪(⍺⍺ ⍵)} is an alternative way to write that without code duplication, and in my extended APL, ⍪⍥{⍵⍴⍨¯3↑1,⍴⍵}.
 
7:30 AM
@nathanrogers I can't see images on the train.
 
@nathanrogers I mean, the train blocks imgur. I'll just look later when I get to the office.
 
oh that's right other countries don't celebrate thanksgiving
I give thanks for the extra days off
(2 3 4⍴⍳6){(⍺⍴⍨¯3↑1,⍴⍺)⍪(⍵⍴⍨¯3↑1,⍴⍵)}(2 3⍴⍳6) or reverse args
I'm not getting something
(⍳2),[¯0.5](2 2⍴⍳4)
also not waht i expected
 
@nathanrogers The planes don't match; 3 4 vs 2 3!
 
oi derp
lol
thanks
 
7:35 AM
@nathanrogers Here you are pairing a rank-1 with a rank-2 and adding a new axis. Expect mess.
@nathanrogers ,[k] requires otherwise conformity. ↑a b will pad with the prototype of a.
 
 
3 hours later…
10:27 AM
@nathanrogers Remove ¨ from indmin[3]: ds←inf@(≤∘0)⍵ for a significant speed-up. If you want even more speed, refactor your formulas to only use real numbers, as complex arithmetic is slow.
 
 
2 hours later…
12:19 PM
@dzaima I just added and noticed a new idiomatic function: ↑⍤⍮ "rank-up". Monadically, it increases the rank by 1. Dyadically, it pairs the arguments along a new leading axis, e.g. two vectors become a matrix, and two matrices become a 3D array. The args have their ranks and shapes aligned appropriately. :-D
 
 
2 hours later…
2:07 PM
CMC: 0 0⍴' '
 
2:21 PM
7 bytes :P
 
2:32 PM
@Quintec Uh, the CMC spec is 7 ⍨ I've got 4. Just discovered it today.
@Quintec Also, there is one obvious byte to save.
 
ngn
2:45 PM
@Adám i got 5: 0/⍪'' still trying...
 
@ngn Yup, I knew someone would find that one, but this one is… unusual. Think out of the box!
 
I get 3 for 0 0⍴⍬, but still trying for ''
 
@Adám Another 5 is ⊢⌸⍨''
 
and another 5-byter ↑⊆⍨''
 
ngn
3:07 PM
@Adám i found it
 
@ngn ⎕NL⍬
 
ngn
@Adám yes :)
{0::⋄(0 0⍴'')≡⍎∊'⎕'⍵'⍬':⎕←⍵}¨,∘.,⍨⎕a
i guessed the general form of the solution and tried all ⎕XY combinations
 
Hey guys, is it possible to set a recursive Dfn to sleep for some time before calling the recursion?
 
@ngn Ah yes, you don't know how to ask the interpreter which 2-letter ⎕-names it knows…
@J.Sallé Sure, ⍺∇⍵⊣⎕DL 3
 
3:23 PM
@Adám oh nice that's what I needed. What does the DL stand for? Also, is 3 the time it'd sleep for?
 
@J.Sallé DeLay, and yes, time in seconds. It returns the actual elapsed time shyly.
 
ngn
@Adám how?
 
Great, I think that's gonna work then
 
@ngn Secret feature ;-) The interpreter can do a lot of stuff we don't tell about.
 
@Adám another thing, is there a way to insert a linefeed in a string other than ⎕TC (Mastering Dyalog APL says that's obsolete but I can't find an alternative)?
 
3:32 PM
@J.Sallé ⎕ucs 10 is what I've seen used everywhere
 
@dzaima Oh nice, thanks!
 
usually as nl←⎕UCS 10⋄... so you don't need to spam parenthesis
 
indeed
 
Maybe even nl←{⍺←⊢ ⋄ ⍺,(⎕UCS 10),⍵} so you can write 'Abc'nl'def'nl'ghi.'
 
I'll only need it once, so just doing ,(⎕UCS 10), works fine for me
 
 
1 hour later…
4:51 PM
@Adám can I have a while-like statement in a Dfn? Basically I need my function to call itself recursively while ⍵≤5, but I also need it to output some text, so the usual cond:true⋄false statement doesn't support that afaik
or should I just make an inner function to do that?
 
@J.Sallé Can you reverse the condition to allow you multiple statements if true?
 
@Adám I think I can. You mean do something like ⍵≥5 instead of ?
It'll add a byte or two but it's not a big deal
 
@J.Sallé No, ⍵>5
 
I need that 5 though so I'll need either ⎕IO←0 or ⍵>6
 
@J.Sallé Alternatively, you can use instead of (and reverse order of statements)
 
5:01 PM
That might also work, lemme try it
 
@J.Sallé I don't get it.
 
@Adám I'll explain, just a sec
Okay so, I'm trying to solve this challenge. Basically, I need to print a fixed string every 2 seconds 5 times, and each time the string needs to be followed by a linefeed and a (randomly selected) . or !.
So basically it'll print string\n for tick 0, then string\n., then string\n.! and so on
Currently I've got {⍵≤5:'Sending 5, 100-byte ICMP Echos, timeout is 2 seconds:',(⎕UCS 10),'.!'[?⍵⍴2]⋄∇(⍵+1)} but it'll obviously only print once
All I need is to print that 6 times (with ⍵=1-⍨⍳6)
@Adám ↑
 
5:21 PM
@J.Sallé Sorry, got distracted.
 
No problem, this is definitely less important than whatever you were doing hahahah
 
@J.Sallé Doesn't this work?:
⋄ {⎕←'Sending 5, 100-byte ICMP Echos, timeout is 2 seconds:',(⎕UCS 10),'.!'[?⍵⍴2]}¨⍳6
 
@Adám
Sending 5, 100-byte ICMP Echos, timeout is 2 seconds:
.
Sending 5, 100-byte ICMP Echos, timeout is 2 seconds:
.!
Sending 5, 100-byte ICMP Echos, timeout is 2 seconds:
!!!
Sending 5, 100-byte ICMP Echos, timeout is 2 seconds:
!.!.
Sending 5, 100-byte ICMP Echos, timeout is 2 seconds:
.!!..
Sending 5, 100-byte ICMP Echos, timeout is 2 seconds:
!.!!.!
 
@Adám nope, there has to be a delay of 2 seconds between outputs (and something else I just noted, the .! must stay in the same order)
that second part will be a pain
 
@J.Sallé Sure, but you can put in a ⎕DL inside the dfn.
 
5:26 PM
also the first message has nothing after the linefeed
 
@J.Sallé What order do you mean?
@J.Sallé ⎕IO←0
@J.Sallé For code golf, you do want the deprecated ,⎕TC[2], instead of (⎕UCS 10) or even use ⎕ML←3 and use ,2↓⎕TC,
 
@Adám I was about to mention that. If the second message has a . after the linefeed, the third needs to have that same dot in that position
 
Getting off train. Later!
 
No problem! I'll probably finish this up tomorrow
 
 
2 hours later…
7:37 PM
holy shit yeah that is a significant speed up! @Adám
 
Nov 6 at 6:17, by dzaima
@nathanrogers a simple way to score the speed of an APL program is count the number of ¨. The more, the worse it'll be.
 
But I mean, from 5 seconds to almost instant
That's crazy
 
@nathanrogers Hey, can you count how many ¨ were in your original code, and how many are there now?
 
@Adám unfortunately as far as complex arithmetic, that's only due to the quadratic formula. The sphere detection formula returns a complex number if it doesn't intersect. Unless there's an alternative sphere intersection formula, I don't know how to get rid of that
 
@nathanrogers OK, but anyway, it is "fast enough" now to be workable, right?
 
7:41 PM
yeah, it's almost instant
even at higher resolutions
with multiple objects
 
@nathanrogers the power of APL when you use it well. :D
 
There weren't many ¨'s there, but there was a lot going on in the ∘. function, now the ∘. is just a simple multiplication, and the new data structure makes it really fast
I had 3 in the original ¨ and 3 ¨ now, ¨ plane ¨sphere and ¨width and height
I did a good job of keeping @dzaima in mind when making my first go :P
but I didn't know about "arrays", and certainly hadn't used anything higher dimensional to solve any problems
 
¨-)
 
so this was a crazy good learning experience
 
@nathanrogers Good. See? You are getting there.
 
7:45 PM
4000 by 2000 resolution took 2 seconds
that's crazy
 
@nathanrogers How long does it take in C++?
 
let me see
 
@nathanrogers I still haven't begun touching 3D+ arrays, so that's one thing you're more experienced at than me :p
 
5 seconds
 
@dzaima We have customers that threaten to give APL up if we don't increase maxrank.
 
7:47 PM
@Adám oh god
 
@nathanrogers Heh, interpreted APL beats compiled C++!
 
this is really good news. uncompiled, this is really fast
 
@nathanrogers And that C++ code is well written, by somebody who knows their stuff?
 
I was using this as sort of a test bed to see if graphical APL would be feasible, and I guess now I know that it is
He's worked on the Witness with johnathan blow, so I'm assuming yes?
I've watched a lot of his content, and he really knows C and the Win32 API for graphical programming inside and out.
He didn't optimize anything, so maybe optimized it would be faster and I'd have to actually time things for real
 
@nathanrogers Well, that kind-of proves my oft-repeated claim that APL often can beat carefully hand-written C/C++ despite APL being written in C/C++.
@nathanrogers I wonder if co-dfns would gain you even more speed.
 
7:50 PM
I am writing @arcfide right now about this version to see if it could be compiled
I'm using codfns for the display, but I don't know how to namespace, or compile things
at 4k resolution, the new one takes 2-3 seconds, the old one takes 45 seconds
incredible
@Adám who is the guy you spoke to about my original version?
 
@nathanrogers Marshall
@nathanrogers how to namespace?
 
yes
I don't understand Dyalog project structure, and namespaces are really wierd. I've tried to make namespaces and then load them, but then it says "not a namesapce"
so I really don't get it
 
@nathanrogers You may want to have a look at Lesson 16.
 
@Adám 30s of looking tells me that doesn't talk much about loading/saving them
 
@nathanrogers To save and load them, look at the end of Lesson 28.
 
7:59 PM
@Adám did you catch my question from last night about how to drop specific ranks?
 
@nathanrogers Uh, no, I think I missed it. Can you link me?
 
@nathanrogers didn't ngn already answer with ⊢/ (or ⊢/[dim])?
 
13 hours ago, by nathan rogers
@ngn how do you drop a dimension?
Just wondering if there was a more standard solution, as I seem to recall a discussion about a specific operator which dropped specific ranks
but that might have been a misunderstanding on my part
 
@nathanrogers I don't think there's anything better than ⊢⌿
dropping a rank if it's exactly one is pretty specific (though I think a built-in type of thing that errors if it's not one would be helpful)
 
@nathanrogers I saw that, but ngn answered right. If you want to drop dimension k, just do ⊢/[k]
 
8:02 PM
ah
there's something goofy going on with the spheres, because each sphere, if hit, will return 2 values
2 matrices, so get the min to get the closest between them
but then if multiple spheres intersect on the same point, I get back multiple lists
 
@nathanrogers Doesn't every ray that hits a sphere have an entry point and an exit point?
 
so I was getting back n x 1 x h x w shapes
yes, but I onlly get the min of the sphere
so the closest hit point
say 3 spheres intersect on the same point, 3 1 h w, would be the shape
so I did ⊢⌿↑⍉
perhaps just ⊢⌿[1]
 
@dzaima oh right something stupid like {÷}⌿ works (as typing ⎕signal is way too much work) :P
 
@dzaima That's actually pretty clever.
 
mindex Pds {(⍺⍴⍨¯3↑1,⍴⍺)⍪(⍵⍴⍨¯3↑1,⍴⍵)} ⊢⌿↑⍉Sds
using your 3d specific append from yesterday
@dzaima I don't get it
 
8:09 PM
@dzaima Hey, you finally found a use for a niladic derived function! (Do you know how to make one?
 
@Adám 2∘+∘3⌿? :D
 
@dzaima Save 2 bytes: 2∘3⌿ (!)
 
@Adám oh I thought that'd be a syntax error all the time, cuz i did 2 . 3 at first
 
@nathanrogers Never mind, we're being silly.
@dzaima . is special :-( 2⍣3/ works too and so too any normal dyadic op.
 
8:12 PM
relatedly, a thing I'd really like in every language to be is a syntactical construct for "TODO" that errors upon getting reached
 
@dzaima Syntactic construct? We tend to write ∘∘∘ or ...
 
@Adám ...⌿1 2 3⍴0 errors immediately though
 
Wat?:
⍞←0⍣0/1 2 3
 
@Adám 3
 
@dzaima Yes, as a I said, . is special (due to nss and ∘. and 2.3)
 
8:14 PM
@Adám so does ∘∘∘⌿1 2 3⍴0
 
@dzaima Yes, because that isn't a valid derived fn.
 
but yeah, that expression is a very special case of requiring erroring
 
@dzaima Sure, but the parser doesn't even manage to make sense of anything. 2∘3 is perfectly OK syntactically.
@DyalogAPL Ah, I get it; you don't care about the left operand if the right operand is 0.
 
@Adám heh, makes sense why that'd happen but still feels strange :p
 
Conditional inline syntax error: 0⍣cond⊢
 
8:18 PM
:D
 
However, I still think a bunch of operators which only take functions as left operand should be extended to treat an array left operand as A⊣⊢
Then you could conditionally replace a value by another with replacement⍣condition⊢normal
@dzaima Hah, I found a shorter (albeit even more obscure) one: 0&/
 
@Adám heh, &/ was one of the first things I tried, forgetting that it's an operator
 
@dzaima This of course works with any monadic operator which doesn't take an array operand (that's all of them, no?)
 
@Adám is an exception
 
@dzaima Ah yes, it only takes a simple scalar positive int.
 

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