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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
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Subject: Re: Constructing an object
Date: Sat, 24 Sep 2005 00:23:01 -0500
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Date: 2005-09-24T00:23:01-05:00
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"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote in message
news:f1idk7ptk100.onel9bzfn1nr$.dlg@40tude.net...
...
> Yes. It must be either a discrete or access type. In the latter case the
> discriminated type has to be limited.

...in Ada 95. In Ada 200Y, access discriminants are allowed on nonlimited
types, but they then cannot have defaults (such discriminants cannot change
after object creation, and we needed to disallow changing them via
assignment).

You also failed to mention that the object factory can be implemented
(probably *ought* to be implemented) with the Ada 200Y
Generic_Dispatching_Constructor. That takes a tag value and a dispatching
function and creates an appropriate object for the tag, initialized by the
dispatching function. While its primary purpose was to make it possible to
implement user-defined T'Class'Input functions, it can be useful in other
circumstances as well (such as construction from a menu).

                       Randy.