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From: Robert A Duff <bobduff@shell01.TheWorld.com>
Newsgroups: comp.lang.ada
Subject: Re: Why no Ada.Wide_Directories?
Date: Thu, 27 Oct 2011 15:39:31 -0400
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Date: 2011-10-27T15:39:31-04:00
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"Yannick Duch�ne (Hibou57)" <yannick_duchene@yahoo.fr> writes:

> Le Thu, 27 Oct 2011 09:43:22 +0200, Dmitry A. Kazakov
> <mailbox@dmitry-kazakov.de> a �crit:
>
>> Note that it was not about multiple inheritance. Yannick suggested that
>> making types like Boolean, String, Integer etc to have classes and
>> primitive operations would mean a performance loss. That is wrong.

> I exactly said this would require program analysis as a whole, at the
> cost  of separate compilation, and thus also at the cost of dropping any
> kind of  library, either shared or static. If any type is potentially
> the root of a  class, then you have to avoid dynamic dispatching every
> where possible,  and to do so, you need global analysis. If you don't,
> you get the direct  performance issues, typical of interpreted languages.

I'm not sure what whole-program analysis you're thinking of.

In Ada, you can tell whether a procedure is dispatching at compile time
of the declaration of that procedure.  And you can tell whether a given
call is dispatching at compile time of that call.  No whole-program
analysis needed.

There would be some overhead when converting a Boolean to Boolean'Class.
A Boolean should fit in 1 byte (or 1 bit if packed).  So you don't want
to store a Tag with every Boolean.  Instead, you want to gin up the
Tag on conversion to class-wide.  But this overhead is not DISTRIBUTED
overhead, so it doesn't matter.

- Bob