In Ocaml, how can I access the Lib module from the command line?

Question

If I type ocaml at the command line and then run code involving e.g. the Lib.explode function, I get the error Error: Unbound module Lib. How can I fix this?

Answer 1

You don't give much to go on. I assume Lib is not the real name, but just an example. You also don't say whether it's a standard OCaml library, a library you have built yourself, or somebody else's library.

Assume it's a library you have built yourself. Then somewhere you have a file named lib.cmo (for a single module) or lib.cma (for an archive of multiple modules). To use such a library from inside the OCaml REPL (the so-called "toplevel"):

$ ocaml
# #load "lib.cmo";;

Or:

$ ocaml
# #load "lib.cma";;

Note that you want to type #load including the #. The first # on the line is the prompt from OCaml. This sometimes makes it confusing to read a transcription of an OCaml session.

After loading the library you can refer to names in the library as you usually would, i.e., as Lib.myfun. You don't refer to them just by the name myfun (as it is sometimes tempting to assume).

Answer 2

You may also wish to use ocamlmktop.

Consider for instance a very basic file test.ml:

let foo = 42

I compile that with the following and now have test.cmo.

ocamlc test.ml

Now I'll create a toplevel with that module available.

% ocamlmktop -o mytop test.cmo 
% ./mytop
        OCaml version 4.13.1

# Test.foo;;
- : int = 42
#