aoc-template

This is an (opinionated) Advent of Code template for solutions in Haskell.

To use:

• Clone this repository
• Set up a new branch for the year's solutions
• Change the package name, update the GitHub link, etc. You'll also want to remove the .cabal file and let stack generate a new one.
• Fill in the solutions and have fun!

When running from the command line you can pass the option -d/--day DAY to run a specific day's solutions. If you do this, then you can also pass -i/--input FILE to specify an input file; by default, the program will look for it in input/DayXX.txt. You can also pass the argument --all-days and all days will be run in order, assuming the input files are in their default places.

Additionally, you can specify the level of detail to print out. By default, the program will print only the answers. If you'd like it to print timing information, use the -t/--timings option. Alternatively, if you'd like it to print the output of the parser and error messages in full, use the -v/--verbose option.

Example usage:

• stack run -- -d 9: Runs Day 9's solutions.
• stack run -- --day 14 --input "wibble.txt": Runs Day 14's solutions, using the input file "wibble.txt".
• stack run -- -d 1 -i "alex.txt" --timings: Runs Day 1's solutions, using the input file "alex.txt". Also prints timing information for each solution.
• stack run -- --all-days: Runs the solutions from all days.

This template can be used with ghcid to compile and run your code every time you save your files. Consider putting the following in your .bashrc (or equivalent):

function day { ghcid --run="Main.performDay (Options (OneDay $1 Nothing) Timings)" }

If sourced in a terminal, running the command day 9, for example, will, open a ghcid session and run your code every time you save, displaying the answers as if you ran the first example command above.

If you think the structure of the Day files needs changing to better suit your needs (before starting the project), then make the appropriate changes in src/Days/Day01.hs and run the apply_changes.zsh file. This will copy Day01 to all the other days, changing Day01 for DayXX as appropriate.

Default Language Extensions

I've turned several language extensions on by default, including the set of stable and reasonable extensions implied by the GHC2021 extension pack. The other extensions enabled by default are:

• GADTs
• LambdaCase
• MultiWayIf
• OverloadedRecordDot
• OverloadedStrings
• RecordWildCards

The reason for these should be pretty clear in most cases. If you want to change the default extensions, the list is in package.yaml.

Default Dependencies

The default package dependencies for this project are:

• directory: This is just for checking if the provided input file exists.
• time: For timing the solutions.
• ansi-term: For colourful pretty printing.
• attoparsec: For the input parser for each day.
• containers: For Map, Set, and so on.
• text: Because Strings are bad.
• optparse-applicative: For command line parsing.
• mtl: Mainly in anticipation that State might be useful. ExceptT is also used to catch exceptions in runDay.
• vector: In anticipation that fixed-length arrays will come in handy.