How to expose sum type constructors to an interface

How to expose sum type constructors to an interface

[Felix Dorner]

Hi,

although this might really be a beginner´ s question I´ ll post it here 
and risk to be eaten by the big fish around here...

I am starting to learn ocaml and tonight´ s lesson is how to handle 
modules/interfaces. I come up with this:

In my implementation file module.ml I define: type aType = A | B
How I now need to expose this Type and its constructors to the 
interface  module.mli, because some of the functions declared in the 
interface take a parameter of type "aType". How can I do this?

Thanks for any help,
Felix

Re: [Caml-list] How to expose sum type constructors to an interface

[Chris King]

On 10/17/07, Felix Dorner <felix_do@web.de> wrote:
> although this might really be a beginner´ s question I´ ll post it here
> and risk to be eaten by the big fish around here...

Well, this small fish is going to nudge you in the direction of the
O'Caml beginners list
(http://tech.groups.yahoo.com/group/ocaml_beginners/) for future
"beginner" questions :)

> In my implementation file module.ml I define: type aType = A | B
> How I now need to expose this Type and its constructors to the
> interface  module.mli, because some of the functions declared in the
> interface take a parameter of type "aType". How can I do this?

Just add "type aType = A | B" to the module.mli file.  As a side note,
if you ever want to see what the inferred signature (i.e. the
signature of a .ml with no .mli) of a module is, run ocaml -i on the
.ml file and it will spit the inferred .mli to standard output.

HTH,
Chris

Re: [Caml-list] How to expose sum type constructors to an interface

[Julien Moutinho]

On Thu, Oct 18, 2007 at 02:16:50AM +0200, Felix Dorner wrote:
> In my implementation file module.ml I define: type aType = A | B
> How I now need to expose this Type and its constructors to the interface  
> module.mli, because some of the functions declared in the interface take a 
> parameter of type "aType". How can I do this?

The toplevel or the flag
  -i  Print inferred interface
may help you :)

% cat file.ml
type a_type = A | B

let f =
    function
    | A -> B
    | _ -> A
% ocamlc -i file.ml
type a_type = A | B
val f : a_type -> a_type

A few pointers that may help too:
http://caml.inria.fr/pub/docs/oreilly-book/html/book-ora130.html#toc180
http://caml.inria.fr/pub/docs/manual-ocaml/manual018.html#@manual.kwd135

Re: [Caml-list] How to expose sum type constructors to an interface

[Christophe Raffalli]

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Julien Moutinho a écrit :
> On Thu, Oct 18, 2007 at 02:16:50AM +0200, Felix Dorner wrote:
>   
>> In my implementation file module.ml I define: type aType = A | B
>> How I now need to expose this Type and its constructors to the interface  
>> module.mli, because some of the functions declared in the interface take a 
>> parameter of type "aType". How can I do this?
>>     
You may also choose not to have a .mli file at all. This is equivalent
to using the result of ocaml -i as mli
file. An mli file is needed if you want to make your type abstract or if
you want to hide some functions.

Cheers,

-- 
Christophe Raffalli
Universite de Savoie
Batiment Le Chablais, bureau 21
73376 Le Bourget-du-Lac Cedex

tel: (33) 4 79 75 81 03
fax: (33) 4 79 75 87 42
mail: Christophe.Raffalli@univ-savoie.fr
www: http://www.lama.univ-savoie.fr/~RAFFALLI
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