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From: matthew_heaney@acm.org (Matthew Heaney)
Subject: Re: Q:Assigning address of variable to pointer ?
Date: 1998/04/16
Message-ID: <matthew_heaney-ya023680001604980057320001@news.ni.net>#1/1
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References: <Pine.BSI.3.95.980415115344.24305B-100000@school.digsys.bg>
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Date: 1998-04-16T00:00:00+00:00
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In article <Pine.BSI.3.95.980415115344.24305B-100000@school.digsys.bg>,
Margarit Nickolov <man@digsys.bg> wrote:

>  type element is record
>     ...
>  end record;
>
>  type p_element is access element;
>
>  e1: element;
>  p_e1: p_element := null;
>
>  begin
>    e1 := some_value;
>    -- now, how to point p_e1 to the variable e1 ?
>    p_e1.all := e1;  -- is that correct ?
>                     -- I have got  exception RANGE_ERROR.
>  end;
>
>
>  I just want to assign 'address' of some dynamic/static allocated memory to 
>'pointer variable'.

You have to declare the object you want to point to as aliased - but
declare a general access type:

type p_element is access all element;

declare
   e1 : aliased element;
   p_e1 : p_element;
begin
   e1 := <some value>;
   p_e1 := e1'access;
end;

Of course, you could always put the object on the heap:

declare
   e1 : element;
   p_e1 : p_element;
begin
   e1 := <some value>;
   p_e1 := new element;
   p_e1.all := e1;
end;

And we can combine steps:

declare
   p_e1 : constant p_element := new element'(<some value>);
begin
   null;
end;