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[Caml-list] Unbound type variables
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Date: -- (:)
From: Patrick M Doane <patrick@w...>
Subject: Re: [Caml-list] Unbound type variables
Interesting - thanks to you and Olivier for pointing this out!

I wasn't aware of how to do this or what the 'constraint' aspect might be
used for.

Patrick

On Thu, 13 Sep 2001, Didier Le Botlan wrote:

> What do you think of a parameterized class ?
> 
> class ['a] c = object
>   method m (x:'a) =
>     match x with
>       | `A -> ()
>       | `B -> ()
>       | `C -> ()
> end
> 
> class [[< `A | `B | `C] as 'b] c :
>   object constraint 'b = 'b method m : 'b -> unit end    
> 
> Beware that the 'a parameter is freezed for each instance of the class,
> that is you cannot call method m twice on the same object with
> incompatible arguments.
> 
> 
> --
> Didier Le Botlan
> http://cristal.inria.fr/~lebotlan
> 

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