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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Constructors with multiple inheritance
Date: Fri, 30 Sep 2011 09:36:20 +0200
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Date: 2011-09-30T09:36:20+02:00
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On Thu, 29 Sep 2011 20:11:53 -0700 (PDT), Rego, P. wrote:

>> This is equivalent to:
>> 
>>     Obj := Construct (Obj.all);
>> 
>> But Obj is null.

> Yes, I agree. But that's the point. I want to reserve the address (so I
> can build my queues from there).

The problem is not the result, but the argument of Construct.

>>> So, how can I fix this?
>> 
>> I don't understand your design, but a constructing function of a
>> non-limited type is just:
>> 
>>    function Construct return Parent_Class;

> It works (and the current code utilizes this approach), but I cannot name
> it a method,

"method" is not an Ada term, but from the OO point of view Construct is a
method, because it is covariant in the result.

> since I cannot call the funtion from inside the class, using
> something like Object.Method.

X.Op is just a syntactic sugar for Op (X). It has nothing to do with an
operation being a method or not, except that in Ada the sugar is allowed
only for certain types of methods, rather than universally.

(The operation Op is a method of the type T in one of its arguments or the
result, when the type of that argument or result is T and Op is covariant
in it.)

> So I need to fix the
> package.function_constructor call and use a call of type
> object.method_constructor.

Why?

What is wrong with the abstract factory pattern?

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de