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From: Robert A Duff <bobduff@shell01.TheWorld.com>
Newsgroups: comp.lang.ada
Subject: Re: Limited_Controlled, orthogonality and related issues
Date: Fri, 19 Jan 2007 10:29:35 -0500
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Date: 2007-01-19T10:29:35-05:00
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Maciej Sobczak <no.spam@no.spam.com> writes:

> So, my simple decision to make T and S controlled required:
>
> 1. Changing the signatures of Do_The_Job and gazillion of similar
> subprograms.
> 2. Adding the tagged keyword in the public view for T and S.
>
> In conclusion, my decision to make T and S controlled appeared to not be
> orthogonal to the rest of the package.

I really can't get too excited about the fact that a change to the
package required other changes to the same package.  If you said
that clients had to change, that would be a much bigger problem.

Possible solutions:

Allow 'Class on untagged types.

Use special syntax to distinguish dispatching operations.

Make all types tagged.  For efficiency, this would require a different
run-time model than what Ada compilers currently do -- you don't want
to store a tag field with every Boolean variable!  To enable the
non-stored-tag model, eliminate the rule that all tagged parameter
are aliased (and allow "aliased" keyword).

None of the above are likely to happen, I suspect.

- Bob