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Date: Fri, 29 Nov 2002 15:03:26 +0100 (CET)
From: Martin Jambon <m.jambon@ibcp.fr>
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To: Alain Frisch <frisch@clipper.ens.fr>
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Subject: Re: [Caml-list] Type aliases
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> You can get something close to what you want with:
>
> module Ints :
> sig
>   type 'a integer
>
>   val int: int -> 'a integer
>   val get: 'a integer -> int
>
>   val ( + ): 'a integer -> 'a integer -> 'a integer
>   val ( * ): 'a integer -> 'a integer -> 'a integer
> (* etc... *)
> end =
> struct
>   type 'a integer = int
>   let int x = x
>   let get x = x
>   include Pervasives
> end

Great! Thanks a lot.

Finally, I decided to define only the 2 conversion functions, since we
have to make difficult choices like the following:

  Should we define   val ( * ) : 'a integer -> 'b integer -> 'b integer
  or                 val ( * ) : 'a integer -> 'a integer -> 'a integer
  or                 val ( * ) : int -> 'a integer -> 'a integer
  ?

So, this is enough to avoid confusion between keys that have the same
representation (commonly int or string) and is complementary to the use
of labeled arguments.
(and no preprocessing is required to make (1 + 1) valid).


Martin

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