I finally found
http://ocaml.org/learn/tutorials/ocamlbuild/Using_internal_libraries.html
(which didn't come up earlier because I was searching for "subdirectory");
following that I added a myocamlbuild file:

 $ cat myocamlbuild.ml
open Ocamlbuild_plugin

let () =
  dispatch begin function
  | After_rules ->
     ocaml_lib "plugins/puz/Puz_plugin";
  | _ -> ()
  end

but then attempting to add to the _tags file:

<file.*>: use_puz_plugin

gave me the following:

Warning: the tag "use_puz_plugin" is not used in any flag or dependency
declaration, so it will have no effect; it may be a typo. Otherwise you can
use `mark_tag_used` in your myocamlbuild.ml to disable this warning.
+ ocamlfind ocamlc -c -g -thread -package core_kernel -I plugins/puz -o
file.cmo file.ml
File "file.ml", line 5, characters 2-17:
Error: Unbound module Puz_plugin


Feedback on the tutorial: It would be useful to have a complete repository
corresponding to each of the examples, that could be checked out and played
with.

martin



On Mon, Sep 21, 2015 at 11:23 PM, Martin DeMello <martindemello@gmail.com>
wrote:

> If I have my project set up like this:
>
> .
> ├── file.ml
> ├── plugins
> │   └── puz
> │       ├── puz_bin.ml
> │       ├── puz_match.ml
> │       ├── puz.ml
> │       ├── puz_plugin.mllib
> │       ├── puz_types.ml
> │       └── puz_utils.ml
> └── _tags
>
> $ cat plugins/puz/puz_plugin.mllib
> Puz Puz_bin Puz_match
>
> This works:
>
> $ ocamlbuild -use-ocamlfind plugins/puz/puz_plugin.cmxa
> Finished, 22 targets (3 cached) in 00:00:03.
>
> My _tags file:
> ------------------------------------------------
> $ cat _tags
> true: thread,debug
> true: package(core_kernel)
>
> "plugins/puz": include
>
> <gui.*>: package(labltk)
> <**/puz.*>: package(unix), package(str), package(core_kernel),
> package(bitstring), package(mikmatch_pcre)
> <**/*_bin.*>: package(bitstring.syntax), syntax(bitstring)
> <**/*_match.*>: package(mikmatch_pcre), syntax(camlp4o)
> ------------------------------------------------
>
> But I can't figure out how to use this library in my main program. This is
> a minimal example of what I'm trying to do, not working of course:
>
> $ cat file.ml
> open Core_kernel.Std
>
> let read fname =
>   let data = In_channel.read_all fname in
>   Puz_plugin.read data
>
> $ ocamlbuild -use-ocamlfind file.native
> + ocamlfind ocamlc -c -g -thread -package core_kernel -I plugins/puz -o
> file.cmo file.ml
> File "file.ml", line 5, characters 2-17:
> Error: Unbound module Puz_plugin
>
> martin
>