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From: vrotney@netcom.com (William Paul Vrotney)
Subject: Re: ANSI CLISP: strengths vs. weaknesses?
In-Reply-To: cracauer@wavehh.hanse.de's message of Sun, 20 Oct 96 11:29:36 GMT
Message-ID: <vrotneyDznMB1.CC@netcom.com>
Organization: NETCOM On-line Communication Services (408 261-4700 guest)
References: <slrn55n3fg.5p.psci@teleport.com> 	<1996Oct10.100654.824@wavehh.hanse.de> <325E98A0.44CD@franz.com> 	<1996Oct18.115909.28857@wavehh.hanse.de> <TMB.96Oct19010039@best.best.com> <1996Oct20.112936.25643@wavehh.hanse.de>
Date: Tue, 22 Oct 1996 01:47:25 GMT
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Sender: vrotney@netcom.netcom.com

In article <1996Oct20.112936.25643@wavehh.hanse.de> cracauer@wavehh.hanse.de (Martin Cracauer) writes:

> 
> tmb@intentionally.blank-see.headers writes:
> 
> >No runtime dispatch mechanism, not even the C++ mechanism, is fast
> >enough to use for "everything".  The only way to be able to give the
> >illusion of treating things like numbers just like other objects is
> >via type inference, immediate representations, and other optimizations.
> 
> >In fact, in practice, the "efficient" C++ dispatch mechanism is not
> >significantly faster than the much more dynamic mechanism found in
> >Objective-C (or, I believe, IBM's SOM).  But the few extra cycles that
> >C++ squeezes out cause lots of headaches when it comes to system
> >integration, dynamic configuration, etc.  In particular, OLE and SOM
> >are really just workarounds for the inflexible and cumbersome object
> >model that C++ has built into it (btw, if you want to know all the
> >unpleasant details, take a look at Lippman's "Inside the C++ Object
> >Model").
> 
> This begins to be off-topic, but the lookup mechanism of ObjC requires
> one pointer indirection more than the C++ virtual function
> call. Pointer indirections can be very expensive given today's memory
> bandwidth/CPU speed relation. 
> 

Actually, I was always in complete agreement with the original poster's
remarks comparing C++ to Objective-C.  I was also under the impression that
pointer indirection was not very expensive on many modern day computers.  So
could you please explain what you mean by this last sentence.



-- 

William P. Vrotney - vrotney@netcom.com
