The APL Orchard

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4:18 AM

Hey y'all. Taking the opportunity afforded by Advent of Code to finally hunker down and learn APL. Having a blast thus far. Today really pushed me in some new directions (recursion and higher order functions: https://git.sr.ht/~adregan/advent-of-code-2021/tree/mainline/item/3.apl)

I was wondering, however, why it isn't necessary to pass the operand through on recursion. Ie. If I have a fn that takes ⍺, ⍺⍺, and ⍵, I only needed to recurse with the arguments: ⍺∇⍵. Do recursive calls share the same scope as the initial call?

1 hour later…

gamma_delta

5:20 AM

Hello, is there a function like segs but also works on more than 1 character?

Simon Branch

5:31 AM

Hi there! Is there any way to replace a given element of a matrix? (i.e. like regular matrix assignment but returning a modified matrix instead of mutating the original)

or more generally, do an operation on only a set of rows or columns

Paul Mansour

5:50 AM

@SimonBranch See the @ operator

(9@2 4)4 3⍴⍳12

gamma_delta

hello, i am having a frusturating problem

i have a list where the second element onward is a string expressing a bingo board

(for aoc)

{↑⍎¨⊃' 'Split(⎕UCS 10)Split ⍵}2⊃input This code will get the board for the second board just fine

but as soon as i try to ¨ that across the entire input, it fails

{↑⍎¨⊃' 'Split(⎕UCS 10)Split ⍵}¨1↓input gives me a value error

AH it's because the file ends in a newline

LdBeth

@gamma_delta not a direct answer to you question, but if you are still struggling with input processing, try github.com/Dyalog/link

gamma_delta

it's driving me crazy yeah

i've been trying to solve it in APL and in a lisp i wrote

doing the input processing is easy in lisp but the actual problem is a nightmare

and inversely, i've been trynig to get apl to read the damn file for like an hour but the problem itelf looks so easy in apl

LdBeth

mkdir Foo; echo "[
0 1 2 3 4
]" > data.apla;

then in Dyalog APL, with Link correctly installed,

]LINK.import Foo Foo
Foo.data
0 1 2 3 4

and with a text editor, you can very easily turning today's input text into apl arrays.

@adr Simple answer, yes. Brief answer: it is like how dynamic scoping is treated in early days lisp.

3 hours later…

xpqz

9:21 AM

@gamma_delta Here's how I read and parsed the data: gist.github.com/xpqz/95303a2498a91cac80efa3cfb6470556

Today's effort was :P -- maybe someone has a smart version; part 1: gist.github.com/xpqz/3853e6e5051f73ba0c7f692e03b2293c

I need to tidy up my p2 a bit...

LdBeth

10:01 AM

I wonder what languages anyone with a rank uses. Probably includes APL, and some other golfing languages with interactive interface.

My personal best is getting #264 in day three's part 1

2 hours later…

klao

12:04 PM

Today's AoC has properly challenged my budding APL knowledge: gist.github.com/klao/b37b9a8f28c8235972ce94e8d6cc9f0e

I'm relatively happy with my solution (no ugly loops, no recursion, no power operator), but still. Would want to simplify the ends thing to be a proper array computation.

xpqz

@klao nice work

klao

@xpqz Thanks! It means a lot!