Ocaml

brew install opam

opam init
# Said "yes" to default config in .zshrc

# Ran this as advised by opam.  I assume it sets the default OCaml compiler as the current compiler.
eval $(opam env --switch=default)

# Install basic libraries used in the book.  `base` is a standard library. `utop` is a top-level REPL
opam install base utop