Solving advent of code challenges in Common Lisp (sbcl)

2021
What is advent of code? homepage
After the hate-love relationship with haskell in last years challenges (love won by a lot) I want to continue trying languages with new concepts I am interested in.
This year, I am trying out common lisp for the first time. I have heard something about macro usage and the REPl integration and will try to play around with that.
Will only do the first 4 days due to time constraints. Might continue, but highly unlikely.

Setup and execution

start sbcl server in current root dir: sbcl --load $HOME/.vim/plugged/vlime/lisp/start-vlime.lisp
connect to sbcl server in vim via vlime
open file for given day, eval main, run main