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From: ytomino <aghia05@gmail.com>
Newsgroups: comp.lang.ada
Subject: Re: discriminant questions
Date: Sun, 18 Sep 2011 16:44:08 -0700 (PDT)
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>>>   X + Y
>> If semantics of smart pointer differs from semantics of value, it may
>> make misunderstanding.
>
> There is no difference, compare it with by-reference parameters. The
> program shall not be written to exploit by-reference vs. by-value. Smart
> pointer is a substitute for what it points to.

Ada has mainly value semantics.
If container is intended to be used as value (like Indefinite_Holder),
"substitutable" is natural.
But if container is intended to be used as access type (like smart
pointer or handle), I think, it is unnatural.
Because we can define another operation having same name for access
type.

type Integer_Access is access Integer;
function "+" (Left : Integer_Access; Right : Storage_Offset) return
Integer_Access;

declare
   a, b : Integer;
   c : Integer_Access; d : Storage_Offset;
begin
   a + b -- sum of integers
   c + d -- address arithmetic
   c.all + d -- sum of referenced integer and offset value
end;

(of course, we usually does not address arithmetic with smart pointer.
this is supposed story.)