From mboxrd@z Thu Jan  1 00:00:00 1970
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From: jsanchor@my-dejanews.com
Subject: Re: Access types
Date: 1998/05/29
Message-ID: <6kmna3$aal$1@nnrp1.dejanews.com>#1/1
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References: <6khbm1$ec1$1@nnrp1.dejanews.com>
 <EtnJAp.8E@jvdsys.nextjk.stuyts.nl>
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Organization: Deja News - The Leader in Internet Discussion
X-Article-Creation-Date: Fri May 29 16:21:24 1998 GMT
Newsgroups: comp.lang.ada
Date: 1998-05-29T00:00:00+00:00
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Well, it's tip of the ice berg.
Package Memory has a subprogram

procedure Checksum(access_to_ram : access Memory_Type'class);--
primitive
--  operation

RAM is declared in another package.
And somebody trying to use checksum will say something like this:

package RAMS is
 type RAM_Type is new Memory.Memory_Type with null record;
 RAM: aliased RAM_Type;
 Memory.Checksum(RAM'access);

end RAMS;

Now my problem is: I want RAM'access to be the same type as Memory_Ptr because
of the nature of my program. But I just can't do it.
I tried casting it, like this
  Ptr_to_memory : Memory_Ptr;

  Ptr_to_memory : Memory_Ptr(access_to_ram); it compiled, but does not run.
Gives me a run time error....PROGRAM_ERROR.


--------------------------------------------------------------------
> What you seem to mean is something like:
>
> 	package Memory is
>
> 	   type Memory_Type is abstract tagged
> 	      record
> 	         null; -- Put the data here
> 	      end record;
>
> 	   type Memory_Ptr is access Memory_Type'Class;
>
> 	   type ROM is new Memory_Type with null record;
>
> 	   type RAM is new Memory_Type with null record;
>
> 	end Memory;
>
> --
> -- Jerry van Dijk  | email: jdijk@acm.org
> -- Leiden, Holland | member Team-Ada
>


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