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From: Geert Bosch <geert@gonzo.sun3.iaf.nl>
Subject: Re: Depending on passing mechanism
Date: 1997/10/21
Message-ID: <62hra6$5j5$1@gonzo.sun3.iaf.nl>#1/1
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References: <hbaker-2010970513390001@10.0.2.1>
 <EIDD1y.8Lz.0.-s@inmet.camb.inmet.com>
Organization: La Calandre Infortunee
Newsgroups: comp.lang.ada
Date: 1997-10-21T00:00:00+00:00
List-Id: <comp.lang.ada>


Tucker Taft <stt@houdini.camb.inmet.com> wrote:
 ``As others have pointed out, in Ada 95 you *do* have control when
   implementing a type to either force by-reference (by making the
   underlying type tagged, protected, task, or limited record)''

For those cases where you do not want a type to be limited, but you
want to enforce passing-by-reference semantics, it is also possible
to use a record with a volatile component.

   type Volatile_Type is null record;
   pragma Volatile (Volatile_Type);

   type Account is record
      Force_By_Reference : Volatile_Type;
      Amount             : Currency_Type;
   end record;

This enforces pass-by-reference semantics for any object of type account
without extra space or time overhead and without limiting assignment. 

Regards,
   Geert