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From: Robert A Duff <bobduff@shell01.TheWorld.com>
Newsgroups: comp.lang.ada
Subject: Re: Limited_Controlled and out parameters
Date: Fri, 22 Jun 2012 17:41:22 -0400
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Date: 2012-06-22T17:41:22-04:00
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Adam Beneschan <adam@irvine.com> writes:

> Can a controlled variable (or subcomponent) ever really be
> uninitialized?

In Ada, the concept of "uninitialized" applies only to scalars.
Access types are initialized by default.  And composite types
have no such notion -- you can only talk about whether none, some,
or all of their scalar subcomponents are initialized.

> I guess it might, or it might be partly uninitialized.  However, if the
> controlled type has a Finalize routine that reads components of the
> type, those components had darn well better not be uninitialized
> garbage.

Right, if scalar.

>...(That is, allowing for cases where, say, a Boolean component
> indicates whether other components in the record are initialized or not.
> But that Boolean had better not be garbage.)

Right.  You can give that Boolean a default.  Or you can make
sure default initialization never happens, for example, by using
unknown discriminants -- "(<>)".

- Bob