Re: [Caml-list] A signature that cannot be inhabited by any structures

[Vincent Aravantinos <vincent.aravantinos@yahoo.fr>]

Le 8 sept. 07 à 09:54, Hyeonseung Im a écrit :

> Hi all.
>
>
>
> I found something interesting. In the OCaml, the following  
> signature is valid. (I tested it with the OCaml version 3.09.2 and  
> 3.10.0.)
>
>
>
> (In the top-level)
>
> # module type S = sig val x : int val x : float end;;
>
> module type S = sig val x : int val x : float end
>
>
>
> But, this module type seems not to be inhabited by any structures.  
> On the contrary, in the SML this sort of module types cannot be  
> defined. (Actually, it raises an error: the duplication of variables.)
>
>
>
> I wonder if this is a feature of the OCaml (or maybe a bug in the  
> implementation).
>
> I’d appreciate any comment on it.
>
>
>
> Hyeonseung Im.
>

Hi,

apart from the question "is this a bug or a feature ?", I'd like to  
say this is quite useful when you want to do some kind of inheritance  
between modules.
See http://caml.inria.fr/pub/ml-archives/caml-list/ 
2007/08/8f1e17b89b64d66ae406521947709aff.en.html for the different  
situation for type replication.

Vincent