OCaml and Opam: unbound module Core

I'm trying to get an OCaml environment set up, and I've followed the instructions from appendix A of the Real World OCaml beta. I set up opam, and installed a version of OCaml with the command

$ opam switch 4.01.0dev+trunk

which passed fine. I then did an

$ eval `opam config env`

to pull in the changes. I'm running the correct top level, as

$ which ocaml

outputs

/home/bryan/.opam/4.01.0dev+trunk/bin/ocaml

I installed the Core package from Jane street, with the command

$ opam install core

Both ocamlfind and opam search show that the package was installed correctly. However when I try to open it either from the repl or in a file, I get the error 'unbound module Core'. e.g.

$ ocaml
# open Core;;
Error: Unbound module Core

Is there something I'm missing here? Why can't OCaml find my installed module?

Solution 1:

So I jumped the gun a bit. I forgot to add some items to my ~/.ocamlinit file. Specifically I forgot to add

#use "topfind"
#camlp4o
#thread
#require "core.top"
#require "core.syntax"

as mentioned in Chapter 1. D'oh!

Solution 2:

Please follow the steps in the Real World OCaml Wiki - Installation Instructions.

Under Setting up and using utop, the instructions state that you should add:

#use "topfind";;
#thread;;
#camlp4o;;
#require "core.top";;
#require "core.syntax";;

to your ~/.ocamlinit file.