AOC 2023

This is a template project for solving Advent Of Code (2023) in Haskell with Nix: fork it and you can start solving!

Setup

You can run nix-shell to get a shell with the intended version of GHC, cabal and HLS. They'll be downloaded if you don't have them already and they won't interfere with any other installation on your system.

You can run commands or your usual editor from that shell or you can use a direnv plugin.

If all is good, cabal build should complete successfully for you.

If you want to use additional packages, you should add them both to aoc2023.cabal (cf. Project config) and shell.nix.

Organization of the codebase

src/ contains all the Haskell code. src/Day01.hs, src/Day02.hs, ... each contain the solution for that specific day, and they are all imported into the src/Main.hs, which is the executable that we use to easily run the solution for the specific day.

data/ dir is where puzzle input files go for each day. Your code in src/DayXX.hs can then read those files as needed. These data files are gitignored, since AoC authors ask not to publicly post your puzzle input files.

Running

Easiest way is calling ./day <num> to run specific day, e.g. ./day 1. You can also run a specific part of one day, e.g. ./day 2 1.

day is really just a helper script for calling cabal run, so you can use cabal run directly if you want more control. cabal run will build all your code (same as cabal build) and then run the executable which has src/Main.hs as its entry point.

cabal repl is also interesting option: it will take you to ghci where all the modules are already loaded for you and you can easily run any function, this is great for debugging and testing, or even normal running. You can just type day01 and run it that way. Type :r to reload upon changes in the code.

Adding new Day

When solving a new Day, lets say Day 17, there are a couple of things you need to set up:

1. Create a new file: src/Day17.hs. Inside it, make sure to update its module name to Day17.
2. Add this module to aoc2023.cabal file, under other-modules, as Day17.
3. Add corresponding input text file to data/ if needed, e.g. data/day17-input.txt or data/day17-1-input.txt.
4. In src/Main.hs, import Day17 and add it to the code.

Project config

This is a cabal-based project.

aoc2023.cabal file already contains the default configuration that should work fine for you.

You will notice it also contains some commented-out extensions and dependencies(packages). These are some common extensions and dependencies that we think you are likely to need so we put them there for your convenience, you just need to uncomment them both in aoc2023.cabal and shell.nix in order to get going with them.

Other templates

1. The base of this one, but using GHCUp instead of Nix: https://github.com/Martinsos/aoc-2023-haskell-template
2. Nice, a bit heavier/richer AoC template (Stack based) that I took some nice ideas from: https://github.com/samcoy3/advent-of-code-template .