In the course of trying to set myself up to follow the Real World OCaml book (using Reason syntax), I ran npm install -g reason-cli in order to get rtop in place of utop (I’m probably wrong, but it looked to me like this was the way it was “meant” to be installed).
Next, I opam install'd core, started rtop, and attempted to #require "core";, which gave me No such package: core.
Out of curiosity, I npm uninstall'd reason-cli, and then opam install'd rtop alone.
I tried again, rtop, #require "core"; (this time it worked), and then open Core; (also worked).
Is this expected behavior? Do I inadvertently have multiple conflicting installations of opam/ocaml?