AOC 2021

These are my solutions to Advent of Code 2021, written in Haskell. Each day can be found in the src folder.

Building

Just run ghc manually on each day in the src folder. Solutions take input from standard input.

There's some scripts to help:

• ./fetch.sh <day>: fetch input for the given day, putting it in the inputs directory.
  • Requires session.key in the containing directory, which must contain your session cookie from the Advent of Code website.
• ./cmp.sh <day>: compile the solution for the given day, outputting to the out directory.
• ./run.sh <day> [--]: run the solution for the given day. Always recompile. If -- is not provided, fetch input (with fetch.sh) if not yet downloaded. With --, just read input from stdin.

What on earth does (($) >>= (.) . ($ (>>)) . (.) . flip (.)) mean?

Most of the solutions have been rewritten in point-free style for fun. These solutions are not meant to be read, and most of them are, in fact, quite incomprehensible. They are almost always entirely equivalent to the normal, "pointful" solutions, which are preserved below the point-free ones, usually with the function name main1.