Down is an unintrusive user experience upgrade for the ocaml toplevel (REPL).
Simply load the zero dependency Down library in the ocaml toplevel and you get line edition, history, session support and identifier completion and documentation (courtesy of ocp-index).
Consult the manual.
Simply run ocaml and load the library:
> ocaml ... # #use "down.top";; Down loaded. Type Down.help () for more info. # List.con^t List.cons : 'a -> 'a list -> 'a list List.concat : 'a list list -> 'a list # List.con
You can add this #use invocation to your ~/.ocamlinit file.
For ocamlnat you will likely have to invoke it with -noinit and you must #use "down.nattop".
More in the manual.
Down An OCaml toplevel (REPL) upgrade