The following assumes that you have managed to get OCaml installed and executing eval $(opam config env) sets up everything correctly in your environment.

The key is to run #require "base";; in utop. The following sequence should work:

#require "core";;
open Base;;
List.map ~f:String.length ["Hello"; "World!"];;

The List.map above is Base.List.map, as desired.

If you don't run #require "core";; you will get the message: Error: Unbound module Base.

#ocaml #learningocaml #utop