Re: [Caml-list] Protected methods

[Gerd Stolpmann <info@gerd-stolpmann.de>]

Alessandro Baretta wrote:
> I'm trying to get the semantics of protected methods of C++. I have a 
> class with a method that is not meaningful for the outside world, but 
> different instances of this class should be able to invoke this method 
> on one another.
> 
> I need something like the following pseudocode:
> 
> class a =
> object
>   method protected m = ...
>   method m2 (obj:a) = a # m
> end
> 
> I understand this can be obtained by creating a container module for 
> class a and restricting the type of a through the module signature. I 
> read the manual but was unable to figure out the syntax to do this. 
> Would anyone be so kind as to lend a hand?

No, you cannot restrict the type of classes by signatures.
The only way I know to protect a method is to define an opaque
type that is hidden by the signature, e.g.

sample.ml:

type protector = unit

class a =
object
   method m () = ...
   ...
end

sample.mli:

type protector

class a :
object
   method m : protector -> XXX
   ...
end

You cannot call m from other modules because you cannot create values
for the type "protector".

Gerd
-- 
------------------------------------------------------------
Gerd Stolpmann * Viktoriastr. 45 * 64293 Darmstadt * Germany
gerd@gerd-stolpmann.de          http://www.gerd-stolpmann.de
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