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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="foreach.portability"></a><a class="link" href="portability.html" title="Portability">Portability</a>
</h2></div></div></div>
<p>
<code class="literal">BOOST_FOREACH</code> uses some fairly sophisticated techniques
that not all compilers support. Depending on how compliant your compiler is,
you may not be able to use <code class="literal">BOOST_FOREACH</code> in some scenarios.
Since <code class="literal">BOOST_FOREACH</code> uses <a href="../../../libs/range/index.html" target="_top">Boost.Range</a>,
it inherits <a href="../../../libs/range/index.html" target="_top">Boost.Range</a>'s
portability issues. You can read about those issues in the <a href="../../../libs/range/doc/html/range/portability.html" target="_top">Boost.Range
Portability</a> section.
</p>
<p>
In addition to the demands placed on the compiler by <a href="../../../libs/range/index.html" target="_top">Boost.Range</a>,
<code class="literal">BOOST_FOREACH</code> places additional demands in order to handle
rvalue sequences properly. (Recall that an rvalue is an unnamed object, so
an example of an rvalue sequence would be a function that returns a <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special">&lt;&gt;</span></code> by value.) Compilers vary in their
handling of rvalues and lvalues. To cope with the situation <code class="literal">BOOST_FOREACH</code>
defines three levels of compliance, described below:
</p>
<div class="table">
<a name="id1261680"></a><p class="title"><b>Table&#160;6.1.&#160;BOOST_FOREACH Compliance Levels</b></p>
<div class="table-contents"><table class="table" summary="BOOST_FOREACH Compliance Levels">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
<p>
Level
</p>
</th>
<th>
<p>
Meaning
</p>
</th>
</tr></thead>
<tbody>
<tr>
<td>
<p>
<span class="bold"><strong>Level 0</strong></span>
</p>
</td>
<td>
<p>
<span class="emphasis"><em><span class="underline">Highest level of compliance</span></em></span><br>
<code class="literal">BOOST_FOREACH</code> works with lvalues, rvalues and
const-qualified rvalues.
</p>
</td>
</tr>
<tr>
<td>
<p>
<span class="bold"><strong>Level 1</strong></span>
</p>
</td>
<td>
<p>
<span class="emphasis"><em><span class="underline">Moderate level of compliance</span></em></span><br>
<code class="literal">BOOST_FOREACH</code> works with lvalues and plain rvalues,
but not const-qualified rvalues.<br> <code class="computeroutput"><span class="identifier">BOOST_FOREACH_NO_CONST_RVALUE_DETECTION</span></code>
is defined in this case.
</p>
</td>
</tr>
<tr>
<td>
<p>
<span class="bold"><strong>Level 2</strong></span>
</p>
</td>
<td>
<p>
<span class="emphasis"><em><span class="underline">Lowest level of compliance</span></em></span><br>
<code class="literal">BOOST_FOREACH</code> works with lvalues only, not rvalues.<br>
<code class="computeroutput"><span class="identifier">BOOST_FOREACH_NO_RVALUE_DETECTION</span></code>
is defined in this case.
</p>
</td>
</tr>
</tbody>
</table></div>
</div>
<br class="table-break"><p>
Below are the compilers with which <code class="literal">BOOST_FOREACH</code> has been
tested, and the compliance level <code class="literal">BOOST_FOREACH</code> provides
for them.
</p>
<div class="table">
<a name="id1261869"></a><p class="title"><b>Table&#160;6.2.&#160;Compiler Compliance Level</b></p>
<div class="table-contents"><table class="table" summary="Compiler Compliance Level">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
<p>
Compiler
</p>
</th>
<th>
<p>
Compliance Level
</p>
</th>
</tr></thead>
<tbody>
<tr>
<td>
<p>
Visual C++ 8.0
</p>
</td>
<td>
<p>
Level 0
</p>
</td>
</tr>
<tr>
<td>
<p>
Visual C++ 7.1
</p>
</td>
<td>
<p>
Level 0
</p>
</td>
</tr>
<tr>
<td>
<p>
Visual C++ 7.0
</p>
</td>
<td>
<p>
Level 2
</p>
</td>
</tr>
<tr>
<td>
<p>
Visual C++ 6.0
</p>
</td>
<td>
<p>
Level 2
</p>
</td>
</tr>
<tr>
<td>
<p>
gcc 4.0
</p>
</td>
<td>
<p>
Level 0
</p>
</td>
</tr>
<tr>
<td>
<p>
gcc 3.4
</p>
</td>
<td>
<p>
Level 0
</p>
</td>
</tr>
<tr>
<td>
<p>
gcc 3.3
</p>
</td>
<td>
<p>
Level 0
</p>
</td>
</tr>
<tr>
<td>
<p>
mingw 3.4
</p>
</td>
<td>
<p>
Level 0
</p>
</td>
</tr>
<tr>
<td>
<p>
Intel for Linux 9.0
</p>
</td>
<td>
<p>
Level 0
</p>
</td>
</tr>
<tr>
<td>
<p>
Intel for Windows 9.0
</p>
</td>
<td>
<p>
Level 0
</p>
</td>
</tr>
<tr>
<td>
<p>
Intel for Windows 8.0
</p>
</td>
<td>
<p>
Level 1
</p>
</td>
</tr>
<tr>
<td>
<p>
Intel for Windows 7.0
</p>
</td>
<td>
<p>
Level 2
</p>
</td>
</tr>
<tr>
<td>
<p>
Comeau 4.3.3
</p>
</td>
<td>
<p>
Level 0
</p>
</td>
</tr>
<tr>
<td>
<p>
Borland 5.6.4
</p>
</td>
<td>
<p>
Level 2
</p>
</td>
</tr>
<tr>
<td>
<p>
Metrowerks 9.5
</p>
</td>
<td>
<p>
Level 1
</p>
</td>
</tr>
<tr>
<td>
<p>
Metrowerks 9.4
</p>
</td>
<td>
<p>
Level 1
</p>
</td>
</tr>
<tr>
<td>
<p>
SunPro 5.8
</p>
</td>
<td>
<p>
Level 2
</p>
</td>
</tr>
<tr>
<td>
<p>
qcc 3.3
</p>
</td>
<td>
<p>
Level 0
</p>
</td>
</tr>
<tr>
<td>
<p>
tru64cxx 65
</p>
</td>
<td>
<p>
Level 2
</p>
</td>
</tr>
<tr>
<td>
<p>
tru64cxx 71
</p>
</td>
<td>
<p>
Level 2
</p>
</td>
</tr>
</tbody>
</table></div>
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<td align="right"><div class="copyright-footer">Copyright &#169; 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>)
</p>
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