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From: wojtek@power.com.pl (Wojtek Narczynski)
Newsgroups: comp.lang.ada
Subject: Re: What evil would happen?
Date: 15 Jul 2003 04:31:16 -0700
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ka@sorry.no.email (Kenneth Almquist) wrote in message news:<bf02o2$dno$1@shell.monmouth.com>...
> wojtek@power.com.pl (Wojtek Narczynski) wrote:
> > I feel like with SML like tagged union datatypes I'd be done long
> > ago... Is there an AI for this maybe?
> 
> I'm not sure what the problem is here.  In SML you can write
> things such as:
> 
>     datatype tree = Leaf of int
>                   | Tree of {
>                         value : int,
>                         left : tree,
>                         right : tree
>                     }
>                   | Empty
> 
> In Ada, you achieve the same effect by writing:
> 
>     type Tree_Tag is (Leaf, General_Tree, Empty);
>     type Tree(Tag : Tree_Tag);
>     type Tree_Ptr is access Tree;
>     type Tree(Tag : Tree_Tag) is record
>         case Tag is
>             when Leaf =>
>                 Leaf : Integer;
>             when General_Tree =>
>                 Value : Integer;
>                 Left : Tree_Ptr;
>                 Right : Tree_Ptr;
>             when Empty =>
>                 null;
>         end case;
>     end record;
> 

Thanks for the example.

Regards,
Wojtek