Advent Of Code

Not necessarily beauty incarnate, the code you'll find in this repository is wild, romantic nature untamed. It is water: sometimes a quiet stream of art, droplets of learning, an ocean of unknown green and blue to be discovered. Other times it will be hideous or hide dark creatures below the sparkling surface.

You aren't supposed to be reading this anyway. The only reason this is not on my private git server is because it is possible that I want to discuss with friends and compare our approaches.

See https://adventofcode.com if you'd like to join in the fun.

Note that I intend to use this to experiment, try new features or hacky things, or learn new languages. So most of the code will not be representative of my quality production code.

The Journey Of The Cursed

'twas the end of the decade, yet life was to continue just as it always did. When a cursed artifact is nearby, you can feel a tingle but only when you touch it, you completely understand just how cursed it actually is. That's why I embarked on the journey through several languages.
And the fun thing about cursed items is that you cannot willingly get rid of them.

Diary Entry of Day 1

Minkolang is awesome! Simple stack machine, makes a bit difficult to store variables, but that works well enough by swapping the top of the stack around.

Only the web interpreter works correctly, the hello world examples of the python version print broken things.

Turns out there are in fact registers and even arrays, I just didn't realize they are there.

Diary Entry of Day 2

HOW IZ I CODIN, VISIBLE "I HAZ ALREADY OPEN IZZUE", GTFO
IF U SAY SO

String operations only exist in version 2.0 of LOLCODE, which is unofficial but also runs on the cray supercomputer and is highly parallelizable. Didn't get that to run

I didn't realize beforehand that segfaults were supposed to happen, but I guess that's fine. LIEK is broken, but what did I expect.

Diary Entry of Day 3 and not yet a half

I expected COBOL to be full of ancient secrets and dark magic. And indeed, magic awaited me. The initial impression of assembly that the few code samples I found in the modern global weave made were a ruse.

It's not just a crumbly scroll, that scroll is alive! Whereas modern languages lack quick-and-deep-dive-tutorials, COBOL has a 100-page Quick Guide for the wizards that don't need the 2017 Programmer's Guide with the full 1000 pages that still somehow lacks useful examples. (In case you need it, check out my Hello World). So of course I reached out into the weave's collection of the hive's ancient knowledge.

The hivemind answered my prayers: "That should be outlined in the fine manual".

In order to find the answers in the tome, you need to already know the spell though. So the goal that had been to create art turned into a quest for survival.

Coding COBOL at 174km/h on foreign territory on new year's first day. Living the l337 live!

TIL: COBOL-CASE is a thing and it's also called TRAIN-CASE

By the Way, COBOL is sentient, and it thinks it is better than java. But even the examples it gives itself show that it's not.

D̰̣͓͍̮̘̹͡i̮̥̟ͅa͙̝̪̬͞r̸y͕̞̭̠ ̷̙͙E̻̟̫͓͈̦ͅn̸͓̩̯̜̣̞̦t̢̯̣̗̪ͅr͏̪y̫̹̼͙̣ ̰͕̱̻ợf̨̠̝̮̣͕̘͕ ̡̤̹̬D͓͚̖͍̼̣ͅa͏y̡̫͚̰̙ ̩̫͎͘4̖̥̦̻̖̤

We planned on using legit. There's a problem with that, though: Legit only treats numbers as numbers when they are hardcoded - otherwise, they're ascii.

Also, the intially compelling weirdness soon became boring. Legit is based on the commit tree instead of the file contents - that's cool. But in order to write useful code, you pretty much need to write another script that generates you your legit tree.

So we instead tried chef. See this file for an example that outputs numbers from 211 to 400 and divides each by 10 as well. It reads like a recipe - somewhat.

However, it turns out that there is neither a way to round floats, nor a way to check for a < b. The only comparison available is a == 0. So to ascertain that digit a is smaller or equal to digit b, one has to loop through every digit possible and check whether they are equal. Hardcoding a 6-fold nested loop for that is possible, but not enticing.

So we decided to use LISP instead. At least it's a programming language that has specs I think.#

Diary Entry of Day $5

Choosing a disputably usable language now, we wrote the latest IntCode Computer using php.

It was less painful than expected, as the weirdnesses resolved quickly. I think it's actually a good thing that my global variables were deemed undefined within the functions. Only this here tripped me up:

Parse error: Invalid numeric literal in ... on line 23

20 ...
21    case 07:
22      return 2;
23    case 08:
24      return 2;
25 ...

The issue is found quickly though: php interprets any number literal (thank goodness it's only literals!) starting with 0 as provided in octal base. Hence, 08 is not valid and would actually need to be written as 010 - or simply as 8.

Diary Entry of Day 6

Bash. It's weirder than expected.

All variables are by default global, even when defined within a function. Functions always return an integer error code, but you can have them echo to stdout and capture the output. Variables need quotes everywhere to avoid them splitting in two words, and set -x outputs the lines to be executed with already replaced variables.

Comparing integers using (( a < b )) is okay but don't do that with strings.

shellcheck.net is nice but only catches half of my mistakes.

Diary Entry of Day 7

Having heard previously from lua, we decided to give it a go. And I was surprised how much it differs from other scripting languages I know. It feels like a union of python and javascript ... or at least of their shortcomings.

Undeclared variables are simply nil and you will only realize that at runtime. Same thing for functions.

Every argument is optional. And functions can return multiple values - if you don't read all of them, the rest will be discarded.

Type checking doesn't really exist.

local a = '0'
print(a .. "is not 0: " .. (a ~= 0))
-- this prints
-- "0 is not 0"
-- but try realizing that the csv of numbers you parsed are actually strings without a type error

Every number is a Double.

Everything is a Table. There are no classes. But there is inheritance on tables.

The multithreading libraries don't really build/install on windows or cygwin.

At least, the for loops are kinda nice - despite table indices counting from 1.

And coroutines are nice too.

$\mathbb{Diary,, Entry,, of,, Day ,,}$8

We're using $\LaTeX$! It's very much not made to perform computations and it shows. This one took me longer than most other Tasks. It takes some getting used to it, but even then - without understanding how $\TeX$ works internally, it's hard to get ahead. And the errors are often so useless that it might just as well only distinguish between "Error" and "No Error". For example, any error within a loop will surface at the end of the loop. Thanks!

But have a look at the output pdf - I wrote that during development. Formatting tricks seem so much easier after trying to use $\TeX$ primitives correctly for a few hours.

Diary.apply { entry Day 9}

Kotlin.

Not much to be said here.

• .also() and .apply() are nice to have
• I simply ported the lua solution from day 7 and added a few mistakes.