One year later, take-two on transitioning from make to dune for an OCaml-based PL course. We have a course library, say, code.cma, stored in a folder outside the dune workspace, say /Users/studentX/lib/, several course projects use the definitions in this course library.

As I understand it, the singular "library" in a dune stanza refers to the artifact created by a build (the output) while the plural "libraries" refers to -inputs- to the current build. How to inform dune about the path to look for non-local .cma files? (As in the include switch > ocamlc -I path ...)? I found the following in the dune documentation:

Finding external libraries
When a library is not available in the workspace, dune will look it up in the installed world, and expect it to be already compiled.

It looks up external libraries using a specific list of search paths. A list of search paths is specific to a given build context and is determined as follow:

if the ocamlfind is present in the PATH of the context, use each line in the output of ocamlfind printconf path as a search path
otherwise, if opam is present in the PATH, use the output of opam config var lib
otherwise, take the directory where ocamlc was found, and append ../lib to it. For instance if ocamlc is found in /usr/bin, use /usr/lib

I didn't know what "A list of search paths is specific to a given build context..." meant but ocamlfind -is- present in the PATH and the command

> ocamlfind printconf path

shows

/Users/muller/.opam/default/lib

seems reasonable (though I suppose I should go sort out exactly the difference between a package and a library). Anyway, I couldn't find a more civilized way to extend ocamlfind's search path so I edited /Users/muller/.opam/default/lib/findlib.conf

by hand to include the path to our course library. Dune still cannot find our course library.

I could be wrong, but it seems this setup (with a standard site library code.cma) is pretty common, so I'm sure I'm missing something super-obvious in the documentation. Any leads would be appreciated.

Bob Muller

On Sun, Jan 13, 2019 at 9:07 AM Nicolás Ojeda Bär <nicolas.ojeda.bar@lexifi.com> wrote:

Dear Bob,

Your present directory structure is just fine. A single `dune` file at `src/dune` with the contents

(executable

(name compile)

(public_name translate))

should be enough. Here I am assuming that all modules in `src/` are part of the compiler. If this is not the case you need to specify the modules you want to include as follows:

(executable

(name compile)

(public_name translate)

(modules compile ast symbol ...))

Note: if you have a file `parser.mly` in your project that needs to be processed with `ocamlyacc` then you need to declare this in its own stanza:

(ocamlyacc parser)

Similarly an `ocamllex` file `lexer.mll` needs to be declared with

(ocamllex lexer)

Finally, you need to make sure there is a `<foo>.opam` file at the root of your project. This file can be be empty if you do not actually use `opam` but the name `foo` is used by `dune` to identify the "package" your executable belongs to. Once these files are in place, you can build your project with

dune build

Best wishes,

Nicolás

On Sun, 13 Jan 2019 at 14:31, Robert Muller <robert.muller2@gmail.com> wrote:

Greetings. I have a toy compiler made up of ~20 modules:

ast.mli ast.ml symbol.mli symbol.ml ...

and a top-level in compile.ml. These sources are compiled and linked using a Makefile which invokes ocamlc. I'll call the resulting compiler "translate".

At present I have *all* of these files resident in a single src/ directory. I'm considering converting the build to dune for the semester. What would the recommended directory structure be and what would the dune file(s?) and stanzas look like? I assume this is in the middle of dune's wheelhouse but I wasn't able to find anything on it in the examples or documents. I assume/hope I don't have to put the modules in a library.

Thank you,
Bob Muller