Compiling multiple Ocaml files

Question

I am new to Ocaml and trying to write some small example application. I am using ocamlc version 3.11.2 under Linux Ubuntu 10.04. I want to compile two files:

Answer 1

First fix the unbound value issue, as explained by Jeffrey's answer. This is a comment about the commands you're using.

Decomposing compilation in several steps is a good way to understand what's going on. If you want to write your own a.mli, most likely to hide some values of the module A, then your command ocaml -i -c a.ml > a.mli is a good way to get a first version of the this file and then edit it. But if you're not touching a.mli, then you don't need to generate it: you can also directly enter

ocamlc -o foo a.ml b.ml

which will produce a.cmo, b.cmo and the exectuable foo.

(It will also generate a.cmi, which is the compiled version of a.mli, that you get by issuing ocamlc -c a.mli. Likewise it will also generate b.cmi).

Note that order matters: you need to provide a.ml before b.ml on the command line. This way, when compiling b.ml, the compiler has already seen a.ml and knows where to find the module A.

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Some more comments:

• You're right in your "As far as I understand" paragraph.
• you don't really include a separate file, it's more like import in Python: the values of module A are available, but under the name A.foo. The contents of a.ml has not been copy-pasted into b.ml, rather, values of the module A, defined in a.ml and it's compiled version a.cmo have been accessed.
• if you're using this module A in b.ml, you can pass any of the following on the command line before b.ml:
  • a.mli, which will get compiled into a.cmi
  • a.cmi if you've already compiled a.mli into a.cmi
  • a.ml or its compiled version a.cmo if you don't need to write your own a.mli, i.e. if the default interface of module A suits you. (This interface is simply every value of a.ml).