You should have nix installed with flakes enabled.
cd day-01
nix runYou should have:
cd day-01
direnv allow
cabal run
ghcidIf you don't have direnv, open a shell with development tools by running nix develop.
For Visual Studio Code, you need these extensions:
If you have direnv, you need to allow the .envrc from the command palette. If not, start Code from a development shell with nix develop.