The famous programming competition: adventofcode.com. Below are instructions on how to run the solutions.
> cat Y2023/input/day-1.txt | cabal run y2023:day-1> cd Y2022
> cat input/day-1.txt | cabal run day-1.hsghc Main.hs
Main DAYMost solutions are single-file and runnable with cabal run <filename.hs>
(or cabal new-run ... if you haven't upgraded to Cabal 3 yet).