The APL Orchard

@Uriel It actually isn't so hard to read, just hard to memorize the primitives. Read left-to-right, then look up each symbol in Atoms/Quicks table and think of it as an APL train.

@Uriel I'll have a go at it, but I think ngn is the right one for this.

Uriel

@Adám I'll try scratching the technique.

Adám

@Uriel A tip: You know that 1 1⍉ is the major diagonal?

Uriel

@Adám now I do

Adám

@Uriel :-) Do you understand why?

Uriel

6:17 PM

@Adám I think I do, given the 3D example in the IDE. but I'm not sure yet

looks like it's working with the same principle of the rank operator

and chooses the plane, vector or space it goes through

Adám

@Uriel Yeah, or n-hyperspace of course

Heh, which language/notation allows you to take the diagonal 4D space out of a 5D space?

Uriel

I still don't understand the implications regarding this tasks

@Adám well, APL. quite useful for wrap drive users in some centuries

Adám

@Uriel It may or may not come in handy. Just a pro-tip.

Uriel

@Adám oh great, thought it was a hint

Adám

@Uriel I have an idea about using ⌺, maybe twice.

Uriel

6:25 PM

@Adám sounds fair considering my 4 outer products

Adám

@Uriel {⊂×⍺}⌺5 5 says for each element which neighbour to add to it.

(where 5 is the matrix size of course)

Uriel

@Adám huh?

doesn't tell me much

Adám

@Uriel So top line is something like ×|×⌊ in APL.

Hey, @Mr.Xcoder you know Jelly, right?

Mr. Xcoder

@Adám Yes, I do.

Uriel

@Adám yea, I guessed that. the bottom line is what looks like gibberish, with the each ops and refferal to other links

Adám

6:33 PM

@Mr.Xcoder Can you explain the Jelly code?

Mr. Xcoder

@Adám Which?

×|×⌊?

Adám

@Mr.Xcoder ^^^^^^^^

Mr. Xcoder

Just a sec.

Uriel

@Adám btw, the trains is the reason that (apart for APL) I favor only golf-langs that uses stack, like 05ab1e and befunge

Mr. Xcoder

Ok, it will take some time.

But what Is it for?

Adám

6:36 PM

A: Fold up a matrix!

Dyalog APL, 101 99 bytes {,/↑,/,/¨(⍉2↑o)(+/+/⍵×∘.{⍺ ⍵∊⍨⌈x}⍨⍳≢⍵)(⊖⍉2↓o←+/¨+/¨⍵∘×¨(0 3 1 2)∘.{⌽∘⍉⍣⍺⊢⍵}(⍳⌊x←.5×≢⍵)∘.=⊂∘.⌈⍨⍳≢⍵)} Try it online! How? m ⍝ the matrix 1 2 3 2 1 0 3 2 3 0 4 2 5 6 3 7 4 7 9 4 0 6 7 2 5 {⍳≢⍵} m ⍝ range of length 1 2 3 4 5 {⊂∘...

Uriel

@Mr.Xcoder RE

Mr. Xcoder

oh Dennis' answer

Adám

I have to get off the train now. I hope to go to bed soon (dead tired). I'll have a look tomorrow what you guys found out.

Mr. Xcoder

@Uriel @Adám So first off, there is a helper link, namely AṂ×Ṡ that, as far as I can tell takes an array of integers, gets the absolute value of each, then gets the minimum absolute value. After that, it maps each integer to 1 if it is positive, 0 if it is 0 and -1 if it is negative and then does vectorized multiplication (of each sign with the minimum absolute value).

I must admit it is very obfuscated.

Uriel

@Adám E"Yers tend to associate tiredness to food consumed on holidays

@Mr.Xcoder and that's only the helper link. wonder what is that for

Mr. Xcoder

6:42 PM

Then there is a Main link, which is gigantic: LH which, as you well guessed gets the length halved

@Uriel Deciphering right now.

caird coinheringaahing

@Mr.Xcoder You mean halved?

Mr. Xcoder

Yes, corrected

@Uriel then ŒR gets the range [−|z|, |z|] inclusive. ṗ2 means Cartesian square, which basically means Cartesian product with itself... Then, Ç€ applies the helper link to the list preceding it (the cartpow).

Uriel

@Mr.Xcoder I figured the single meanings (see pic up). I just don't get how they sum up together

Mr. Xcoder

Ok, the large description is mainly for myself.

(it is hard to decipher Dennis' cryptic posts)

ok, so this is the output for the first matrix:

Using the code:

AṂ×Ṡ
LHŒRṗ2Ç€

If you now group the indices by their values, you'll get:

 2  6  7
 4  9 10
 1
 5
 3  8 11 12 13 14 15 18 23
16 17 22
19 20 24
21
25

Median gives us 6 9 1 5 1 3 1 7 2 0 2 1 2 5

@cairdcoinheringaahing Can you please find another challenge for JHT in the elapsed time?

caird coinheringaahing

@Mr.Xcoder Yeah, that's what I'm doing. There aren't a lot without Jelly answers :(

Mr. Xcoder

6:52 PM

@Uriel TBH I have no idea how he did it. Just comment asking for a detailed explanation --- It's far more obfuscated than I thought.

Adám

7:07 PM

Cool, local bus has wifi.

caird coinheringaahing

@Adám Yeah, they've introduced that here, along with on-board phone chargers. Great isn't it?

Uriel

@Adám well, I guess local in UK is regional for us. Maybe national?

Uriel

7:34 PM

A: Fold up a matrix!

Jelly, 25 23 21 bytes AṂ×ṠṚ LHŒRṗ2Ç€ḅLĠịFS€ Try it online! Background (WIP) We start by replacing its elements with coordinates, increasing leftwards and downwards and placing (0, 0) in the center of the matrix. For a 7x7 matrix M, we get the following coordinates. (-3,-3) (-3,-2) (-3,-1) ...

dude is totally brilliant

Uriel

7:58 PM

@Adám codegolf.stackexchange.com/a/145238/65326 something to work with

I really liked the x××× part

Adám

8:43 PM

@Uriel +/¨+/¨ can be +/∘,¨ or +/∘∊¨ depending on argument.

@Uriel ∪/∪/ → ∪/,

@Uriel {(+/1x×××⌊/∘|)⍺⍵} → ((+/1x×××⌊/∘|),)

Uriel

9:08 PM

@Adám thanks!

Adám

@Uriel I'm writing up a totally different approach at same length.

Uriel

@Adám the more the merrier

yet, my original solution resembled vaguely Dennis'. the main advantage of the last one is the early determination of order (with p+nq)

Adám

9:36 PM

A: Fold up a matrix!

APL (Dyalog), 60 bytes* In collaboration with my colleague Marshall. Anonymous prefix lambda. Takes matrix as argument and returns vector. Assumes ⎕IO (Index Origin) to be zero, which is default on many systems. {(,⍉{+/,(s×-×⍺)↓⍵×i∊¨⍨s←⌊⊃r÷2}⌺r⊢⍵)/⍨,(⊢∨⌽)=/¨i←⍳r←⍴⍵} Try it online! {…} ano...

Really cool use of ⌺'s left argument, if I may say so.

(Mine is shorter, but has more bytes.)

Uriel

@Adám really cool approach. I still win 😈

Adám

@Uriel Only because PPCG's byte counting for APL is silly. On codegolf.co.uk, I would have won.

Uriel

@Adám just noticed that if APL answers were half my answers I'd have 12*2 answers, and apparently I have 13*2. this proves that the time it takes to adapt to * as the power symbol is ≤ than the time where code golfing damages your brain

Adám

9:54 PM

@Uriel I think this statement proves that you need to get some sleep.

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