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Subject: Re: [boost] [utility] new auto_buffer class --- RFC
From: David Abrahams (dave_at_[hidden])
Date: 2009-03-18 07:54:17

on Sat Mar 14 2009, Thorsten Ottosen <> wrote:

> David Abrahams skrev:
>> A class that attempts to provide value semantics but doesn't support x = x is
>> putting a big hole in the system of equational reasoning. Justifying that (to me)
>> would take some pretty heavy proof.
> I have not really seen code that exhibits x = x. I've seen lot's of discussion
> (e.g. Sutter & Meyers). Does anybody write such code?

Yes, it happens. It doesn't happen that way, of course. It happens in
x = y when x and y happen to refer to the same object.

Regardless, as I've been saying, the burden of proof runs in the other
direction. You need to show a /realistic/ benchmark that suffers
significantly. And don't bias the test unfairly, either: you only need
the self-assignment check in your slow branch, the one that does the

The great computer scientists that came before us have shown us the way.

Dave Abrahams
BoostPro Computing

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