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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: limited agregate and limited components default initialization
Date: Mon, 2 Apr 2018 14:11:59 +0200
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Xref: reader02.eternal-september.org comp.lang.ada:51294
Date: 2018-04-02T14:11:59+02:00
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On 2018-04-02 13:25, Jean-Claude Rostaing wrote:
> It works, so much for "impossible" dmitry.
> 
> I probably read before the implementation you mentioned, I don't remember exactly. I saw something strange writing this. Shouldn't the expression function
> function GET (Pointer : Pointer_Type) return Accessor_Type is
>       (if Pointer.Pointer = null or else POINTER.Pointer.Value = null then raise EXC_NULL_POINTER_ACCESS
>        else ACCESSOR_TYPE'(Data_Link => Pointer.Pointer.Value));
> be strictly equivalent to
> function GET (Pointer : Pointer_Type) return Accessor_Type is
>     begin
>        if Pointer.Pointer = null or else POINTER.Pointer.Value = null then raise EXC_NULL_POINTER_ACCESS;
>        else
>           return ACCESSOR_TYPE'(Data_Link => Pointer.Pointer.Value);
>        end if;
>     end GET;
> ? Yet no, the second is fine, the second raises at run time
> raised CONSTRAINT_ERROR : pointers.adb:20 discriminant check failed

You still cannot dereference you smart pointer without an explicit call 
to Get. You could just make Get returning an anonymous access to the 
target and be done with that.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de