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From: Maciej Sobczak <see.my.homepage@gmail.com>
Newsgroups: comp.lang.ada
Subject: Equivalent of dynamic_cast (downcast) for tagged types
Date: Thu, 27 Jan 2011 07:46:33 -0800 (PST)
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Date: 2011-01-27T07:46:33-08:00
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Hi,

Unfortunately I need to HACK some equivalent of dynamic_cast in Ada.

There is a limited tagged type T deriving from Limited_Controlled and
Some_Interface as well.
There is also a procedure like this:

procedure Foo (X : in Some_Interface'Class);

Inside Foo I would like to check if X is indeed T and if so, I would
like to dynamic_cast to it and execute some operation on T. That
operation is in fact declared in Some_Interface anyway, but I would
like to avoid the dispatching call. I would also like to avoid any
potential data copying, so access types are welcome.

In C++ it would look like this:

void foo(some_interface & x)
{
    T * p = dynamic_cast<T*>(&x);
    if (p != NULL)
    {
        // indeed x is of type T
        p->do_something_for_me();
    }
}

If you say that I should not do this because it is not good practice,
then I will quickly answer that GNAT should not randomly call Adjust
on my limited (!) objects.

Thank you for your help.

--
Maciej Sobczak * http://www.inspirel.com