type constraints involving variant types

type constraints involving variant types

[Christian Sternagel]

Is it possible to give type constraints involving variant types?
If there is e.g.

module type A = sig
 type t = A of 'a | B of 'b
end

module type B = sig
 module A : A
end

Can I then do something like

module type C = sig
 module B : B
 module A : A
  with type t = B.A.t = A of 'a | B of 'b
end

The above yields a syntax error, but there should be a way of doing
that or not?

cheers

christian

Re: type constraints involving variant types

[Zheng Li]

Not sure if this is what you want:

# module type C = sig
    module A: A
    module B: B with module A = A
  end;;
module type C =
  sig
    module A : A
    module B : sig module A : sig type t = A.t = A of int | B of string end end
  end

Christian Sternagel <christian.sternagel@uibk.ac.at> writes:
> module type A = sig
>  type t = A of 'a | B of 'b
> end
>
> module type B = sig
>  module A : A
> end
>
> Can I then do something like
>
> module type C = sig
>  module B : B
>  module A : A
>   with type t = B.A.t = A of 'a | B of 'b
> end
>

-- 
Zheng Li
http://www.pps.jussieu.fr/~li

Re: [Caml-list] Re: type constraints involving variant types

[Christian Sternagel]

On Fri, Mar 16, 2007 at 02:07:50PM +0100, Zheng Li wrote:
> 
> Not sure if this is what you want:
> 
> # module type C = sig
>     module A: A
>     module B: B with module A = A
>   end;;
> module type C =
>   sig
>     module A : A
>     module B : sig module A : sig type t = A.t = A of int | B of string end end
>   end
Thanks a lot! That finally worked... after days of type contraints, the obvious solutions get somehow lost.

cheers

christian
> 
> Christian Sternagel <christian.sternagel@uibk.ac.at> writes:
> > module type A = sig
> >  type t = A of 'a | B of 'b
> > end
> >
> > module type B = sig
> >  module A : A
> > end
> >
> > Can I then do something like
> >
> > module type C = sig
> >  module B : B
> >  module A : A
> >   with type t = B.A.t = A of 'a | B of 'b
> > end
> >
> 
> -- 
> Zheng Li
> http://www.pps.jussieu.fr/~li
> 
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