Re: [Caml-list] automatic extaction of the .mli (and a little more) from the .ml

[Alain Frisch <alain@frisch.fr>]

On 06/04/2013 09:53 AM, David Allsopp wrote:
> I have wondered if this problem is perhaps looked at the wrong way
> around - in other words, the complaint takes the form "how can we
> export to the .mli file automatically" rather than "how can we
> *import* from the .ml file automatically". The thing I do find
> irritating maintaining .mli/.ml files is having to type anything out
> twice - and for the most part that means fully exported type
> declarations. Say you have a simple module:

I'd rather do it the other way around: maintain the type declaration in 
the .mli and import it in the .ml file.

And, guess what, there is also a POC of such a tool in the 
extension_points branch.  It allows you to write in the .ml file:

   type t = [%copy_typedef]

to copy the concrete definition from the .mli file.  This also works for 
module types, and you can also import a definition from another .ml or 
.mli file:

   module type S = [%copy_typedef]
   type loc = [%copy_typedef "../../parsing/location.mli" t]


The [%id ...] syntax is the other new syntactic feature introduced by 
the extension_points branch (in addition to attributes).  Contrary to 
attributes which annotate already well-formed code and which can thus be 
ignored by the type-checker, [%...] extensions can used in place of an 
expression, type, pattern, etc, and they need to be expanded by a -ppx 
rewriter.



The tool:

http://caml.inria.fr/cgi-bin/viewvc.cgi/ocaml/branches/extension_points/experimental/frisch/copy_typedef.ml?revision=HEAD&view=markup

And an example:

http://caml.inria.fr/cgi-bin/viewvc.cgi/ocaml/branches/extension_points/experimental/frisch/test_copy_typedef.mli?revision=HEAD&view=markup

http://caml.inria.fr/cgi-bin/viewvc.cgi/ocaml/branches/extension_points/experimental/frisch/test_copy_typedef.ml?revision=HEAD&view=markup



-- Alain