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Date: Wed, 25 Mar 2009 12:40:44 +0100
From: Georg Bauhaus <rm.dash-bauhaus@futureapps.de>
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Subject: Re: Ada-Singleton-Why does it work like this?
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patrick.gunia@googlemail.com schrieb:
> Yet another question, if my Singleton_Type is unconstrained, why does
> Ada allow creating Access-Types to unconstrained types allowing to
> access there record-properties, while not allowing to create an
> instance of Singleton_Type directly?

This is wrong, see below.

> if I declare a pointer in C++ I
> either have to create a new instance using "new" in heap-memory where
> the pointer points to or I have to use references and then let the
> pointer point to a reference.

Same in Ada. Although, you have to use "aliased" before an object
(or have an object that is implicitly aliased) if you want to use
C++::&.

> In both cases I first have to create an
> object and then let the pointer point to it.

Same in Ada.

> When I use access types
> in Ada in my example it�s possible to create a pointer to a class

Nitpick: You can't point to a class, only to objects.

> which can�t be instantiated, because it is unconstrained.

(Nitpick: you instantiate generic units, you create objects.)
Objects of type Singleton_Type can be created.
They cannot, however, be created outside the package Singleton.

HTH