neilnjae, 
Day 4 done, still in Haskell, simpler than the past couple now we're out of the weekend.
A little bit of thought led to a pretty neat solution, I think.
Full writeup at https://work.njae.me.uk/2023/12/04/advent-of-code-2023-day-04/
Code at https://gitlab.com/NeilNjae/advent-of-code-23/-/blob/main/advent04/Main.hs
