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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
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<a name="foreach.history_and_acknowledgements"></a><a class="link" href="history_and_acknowledgements.html" title="History and Acknowledgements">History and Acknowledgements</a>
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</h2></div></div></div>
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<h3>
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<a name="foreach.history_and_acknowledgements.h0"></a>
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<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>
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</h3>
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<p>
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The ideas for <code class="literal">BOOST_FOREACH</code> began life in the Visual C++
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group at Microsoft during the early phases of the design for C++/CLI. Whether
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to add a dedicated "foreach" looping construct to the language was
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an open question at the time. As a mental exercise, Anson Tsao sent around
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some proof-of-concept code which demonstrated that a pure library solution
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might be possible. The code was written in the proposed C++/CLI dialect of
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the time, for which there was no compiler as of yet. I was intrigued by the
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possibility, and I ported his code to Managed C++ and got it working. We worked
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together to refine the idea and eventually published an article about it in
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the November 2003 issue of the CUJ.
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</p>
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<p>
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After leaving Microsoft, I revisited the idea of a looping construct. I reimplemented
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the macro from scratch in standard C++, corrected some shortcomings of the
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CUJ version and rechristened it <code class="literal">BOOST_FOREACH</code>. In October
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of 2003 I began a discussion about it on the Boost developers list, where it
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met with a luke-warm reception. I dropped the issue until December 2004, when
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I reimplemented <code class="literal">BOOST_FOREACH</code> yet again. The new version
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only evaluated its sequence expression once and correctly handled both lvalue
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and rvalue sequence expressions. It was built on top of the recently accepted
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<a href="../../../libs/range/index.html" target="_top">Boost.Range</a> library, which
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increased its portability. This was the version that, on Dec. 12 2004, I finally
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submitted to Boost for review. It was accepted into Boost on May 5, 2005.
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</p>
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<h3>
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<a name="foreach.history_and_acknowledgements.h1"></a>
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<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>
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</h3>
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<p>
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Thanks go out to Anson Tsao of Microsoft for coming up with the idea and demonstrating
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its feasibility. I would also like to thank <a href="http://boost.org/people/thorsten_ottosen.html" target="_top">Thorsten
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Ottosen</a> for the <a href="../../../libs/range/index.html" target="_top">Boost.Range</a>
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library, on which the current version of <code class="literal">BOOST_FOREACH</code> is
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built. Finally, I'd like to thank Russell Hind, Alisdair Meredith and Stefan
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Slapeta for their help porting to various compilers.
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</p>
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<h3>
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<a name="foreach.history_and_acknowledgements.h2"></a>
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<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
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Reading</a>
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</h3>
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<p>
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For more information about how <code class="literal">BOOST_FOREACH</code> works, you
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may refer to the article <a href="http://www.artima.com/cppsource/foreach.html" target="_top"><span class="quote">“<span class="quote">Conditional
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Love</span>”</span></a> at <a href="http://www.artima.com/cppsource/" target="_top">The C++
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Source</a>.
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</p>
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</div>
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<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
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<td align="left"></td>
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<td align="right"><div class="copyright-footer">Copyright © 2004 Eric Niebler<p>
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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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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