[Caml-list] renaming a type

[Caml-list] renaming a type

[Pascal Brisset]

 I want to alias a type outside a module in order to use it easily
without opening the module.
 For example

sepia[211]% ocaml
        Objective Caml version 3.01

# module M = struct type t = T end;;
module M : sig type t = T end
# type t' = M.t = T;;
type t' = M.t = T
# T = M.T;;
- : bool = true

 Unfortunately it does not work is I instantiate a polymorphic type with the
same idea:

# module M = struct type 'a t = T end;;
module M : sig type 'a t = T end
# type t' = int M.t = T;;
       ^^^^^^^^^^^^^^^^
The variant or record definition does not match that of type int M.t

Is there a workaround to get the expected result: writing, without prefixing
the module name, values of a type defined in a module and aliased outside ?

--Pascal
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Re: [Caml-list] renaming a type

[Francois Pottier]

>  Unfortunately it does not work is I instantiate a polymorphic type with the
> same idea:
> 
> # module M = struct type 'a t = T end;;
> module M : sig type 'a t = T end
> # type t' = int M.t = T;;
>        ^^^^^^^^^^^^^^^^

Why not do it in two steps?

# module M = struct type 'a t = T end;;
module M : sig type 'a t = T end
# type 'a t' = 'a M.t = T;;
type 'a t' = 'a M.t = T
# type t'' = int t';;
type t'' = int t'

Clearly very clumsy, of course, but it works.

-- 
François Pottier
Francois.Pottier@inria.fr
http://pauillac.inria.fr/~fpottier/
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