Advent Of Code

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An unofficial home for the advent of code community on programming.dev! Other challenges are also welcome!

Advent of Code is an annual Advent calendar of small programming puzzles for a variety of skill sets and skill levels that can be solved in any programming language you like.

Everybody Codes is another collection of programming puzzles with seasonal events.

AoC 2025

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⚙️ - 2023 DAY 19 SOLUTIONS -⚙️ (programming.dev)

submitted 2 years ago* (last edited 2 years ago) by CameronDev@programming.dev to c/advent_of_code@programming.dev

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Day 19: Aplenty

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[–] sjmulder 2 points 2 years ago (1 children)

That's a nice parser and I like the use of pattern matching here.

What I wonder is if you couldn't make a cool monadic representation of the ranges, where you could do the equivalent of

if (foo.x > 12)
    return bar(x);
else
    return baz(x);

but 'x' wouldn't be an integer, it'd be a collection of integer ranges. The > operator would return a collection of pairs of (newly split) integer ranges and booleans. The if would yield map the pairs to a new bunch of pairs and so on.

[–] lwhjp 2 points 2 years ago

Mmm, I was thinking something similar. I've been meaning to go back and have another go, but the last few problems have eaten up all my time (and energy!)

I realized with the parser you can write eg

    rule = (,) <$> optionMaybe (try condition) <*> many1 letter

which avoids even more of those pesky variable names! (I still haven't quite internalized how to use Applicative)