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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="foreach.history_and_acknowledgements"></a><a class="link" href="history_and_acknowledgements.html" title="History and Acknowledgements">History and Acknowledgements</a>
</h2></div></div></div>
<h3>
<a name="foreach.history_and_acknowledgements.h0"></a>
<span class="phrase"><a name="foreach.history_and_acknowledgements.history"></a></span><a class="link" href="history_and_acknowledgements.html#foreach.history_and_acknowledgements.history">History</a>
</h3>
<p>
The ideas for <code class="literal">BOOST_FOREACH</code> began life in the Visual C++
group at Microsoft during the early phases of the design for C++/CLI. Whether
to add a dedicated "foreach" looping construct to the language was
an open question at the time. As a mental exercise, Anson Tsao sent around
some proof-of-concept code which demonstrated that a pure library solution
might be possible. The code was written in the proposed C++/CLI dialect of
the time, for which there was no compiler as of yet. I was intrigued by the
possibility, and I ported his code to Managed C++ and got it working. We worked
together to refine the idea and eventually published an article about it in
the November 2003 issue of the <a href="http://www.cuj.com" target="_top">CUJ</a>.
</p>
<p>
After leaving Microsoft, I revisited the idea of a looping construct. I reimplemented
the macro from scratch in standard C++, corrected some shortcomings of the
CUJ version and rechristened it <code class="literal">BOOST_FOREACH</code>. In October
of 2003 I began a discussion about it on the Boost developers list, where it
met with a luke-warm reception. I dropped the issue until December 2004, when
I reimplemented <code class="literal">BOOST_FOREACH</code> yet again. The new version
only evaluated its sequence expression once and correctly handled both lvalue
and rvalue sequence expressions. It was built on top of the recently accepted
<a href="../../../libs/range/index.html" target="_top">Boost.Range</a> library, which
increased its portability. This was the version that, on Dec. 12 2004, I finally
submitted to Boost for review. It was accepted into Boost on May 5, 2005.
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<a name="foreach.history_and_acknowledgements.h1"></a>
<span class="phrase"><a name="foreach.history_and_acknowledgements.acknowledgements"></a></span><a class="link" href="history_and_acknowledgements.html#foreach.history_and_acknowledgements.acknowledgements">Acknowledgements</a>
</h3>
<p>
Thanks go out to Anson Tsao of Microsoft for coming up with the idea and demonstrating
its feasibility. I would also like to thank <a href="http://boost.org/people/thorsten_ottosen.html" target="_top">Thorsten
Ottosen</a> for the <a href="../../../libs/range/index.html" target="_top">Boost.Range</a>
library, on which the current version of <code class="literal">BOOST_FOREACH</code> is
built. Finally, I'd like to thank Russell Hind, Alisdair Meredith and Stefan
Slapeta for their help porting to various compilers.
</p>
<h3>
<a name="foreach.history_and_acknowledgements.h2"></a>
<span class="phrase"><a name="foreach.history_and_acknowledgements.further_reading"></a></span><a class="link" href="history_and_acknowledgements.html#foreach.history_and_acknowledgements.further_reading">Further
Reading</a>
</h3>
<p>
For more information about how <code class="literal">BOOST_FOREACH</code> works, you
may refer to the article <a href="http://www.artima.com/cppsource/foreach.html" target="_top"><span class="quote">“<span class="quote">Conditional
Love</span>”</span></a> at <a href="http://www.artima.com/cppsource/" target="_top">The C++
Source</a>.
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<td align="right"><div class="copyright-footer">Copyright © 2004 Eric Niebler<p>
Distributed under the Boost Software License, Version 1.0. (See accompanying
file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
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