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51 KiB
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<html>
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<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
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<title>Boost.MultiIndex Documentation - Compiler specifics</title>
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<link rel="stylesheet" href="style.css" type="text/css">
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</head>
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<body>
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<h1><img src="../../../boost.png" alt="boost.png (6897 bytes)" align=
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"middle" width="277" height="86">Boost.MultiIndex Compiler specifics</h1>
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<div class="prev_link"><a href="reference/key_extraction.html"><img src="prev.gif" alt="key extraction" border="0"><br>
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Key extraction
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</a></div>
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<div class="up_link"><a href="index.html"><img src="up.gif" alt="index" border="0"><br>
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Index
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</a></div>
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<div class="next_link"><a href="performance.html"><img src="next.gif" alt="performance" border="0"><br>
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Performance
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</a></div><br clear="all" style="clear: all;">
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<hr>
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<p>
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Boost.MultiIndex has been tried in different compilers, with
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various degrees of success. We list the limitations encountered,
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along with suitable workarounds when available.
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</p>
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<h2>Contents</h2>
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<ul>
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<li><a href="#bcb_64">Borland C++ Builder 6.4</a></li>
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<li><a href="#comeau_433_win_vc7_71">Comeau C/C++ 4.3.3 for Windows (VC++ 7.0/7.1 backend)</a></li>
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<li><a href="#compaq_65">Compaq C++ 6.5-042 for Tru64 UNIX</a></li>
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<li>
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<a href="#gcc_32">GNU GCC 3.2 and later</a>
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<ul>
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<li><a href="#gcc_tru64">GNU GCC for Tru64 UNIX</a></li>
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<li><a href="#gcc_4_darwin">Darwin GCC 4.0</a></li>
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</ul>
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</li>
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<li><a href="#acc_60">HP aC++ A.06.00 for HP-UX</a></li>
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<li><a href="#va_60">IBM VisualAge C++ V6.0 for AIX</a></li>
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<li><a href="#intel_71_8x_lin">Intel C++ Compiler for Linux 7.1/8.0/8.1</a></li>
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<li><a href="#intel_em64t_81_lin">Intel C++ Compiler Extended Memory 64 Technology 8.1 for Linux</a></li>
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<li><a href="#intel_7x_win">Intel C++ Compiler for Windows 32-bit 7.0/7.1</a></li>
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<li><a href="#intel_71_win_stlport_453">Intel C++ Compiler for Windows 32-bit 7.1 + STLport 4.5.3</a></li>
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<li><a href="#intel_8x_9x_win">Intel C++ Compiler for Windows 32-bit 8.0/8.1/9.0</a></li>
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<li><a href="#cw_83_9x">Metrowerks CodeWarrior 8.3 and later</a></li>
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<li><a href="#msvc_60">Microsoft Visual C++ 6.0 Service Pack 5</a></li>
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<li><a href="#msvc_60_stlport_453">Microsoft Visual C++ 6.0 Service Pack 5 + STLport 4.5.3</a></li>
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<li><a href="#msvc_70">Microsoft Visual C++ 7.0</a></li>
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<li><a href="#msvc_71">Microsoft Visual C++ 7.1</a></li>
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<li><a href="#msvc_80">Microsoft Visual C++ 8.0</a></li>
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<li><a href="#portability">Portability techniques</a>
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<ul>
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<li><a href="#member_offset">Use of <code>member_offset</code></a></li>
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<li><a href="#mem_fun_explicit">Use of <code>const_mem_fun_explicit</code> and
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<code>mem_fun_explicit</code></a></li>
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<li><a href="#composite_key_no_pts"><code>composite_key</code> in compilers
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without partial template specialization</a></li>
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<li><a href="#symbol_reduction">Reduction of symbol name lengths</a>
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<ul>
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<li><a href="#argument_limitation">Limitation of maximum number of arguments</a></li>
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<li><a href="#type_hiding">Type hiding</a></li>
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</ul>
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</li>
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</ul>
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</li>
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</ul>
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<h2><a name="bcb_64">Borland C++ Builder 6.4</a></h2>
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<p>
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Currently, Boost.MultiIndex cannot be used with BCB 6.4. The
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number of problems encountered during the tests makes it unlikely that
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future versions of the library can be made to work under
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this compiler.
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</p>
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<h2><a name="comeau_433_win_vc7_71">Comeau C/C++ 4.3.3 for Windows (VC++ 7.0/7.1 backend)</a></h2>
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<p>
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No problems have been detected with this compiler. The library fails to compile,
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however, when Microsoft Visual C++ 6.0 is used as the backend.
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</p>
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<h2><a name="compaq_65">Compaq C++ 6.5-042 for Tru64 UNIX</a></h2>
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<p>
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No problems have been detected with this compiler.
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</p>
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<h2><a name="gcc_32">GNU GCC 3.2 and later</a></h2>
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<p>
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No problems have been detected with several versions of this compiler
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starting from 3.2. The following versions have been explicitly tested:
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<ul>
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<li>GCC 3.2 20020903 under Linux,</li>
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<li>GCC 3.2 20020927 (prerelease) under Cygwin 1.5.7,</li>
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<li>GCC 3.2.3 under Linux, (mingw special 20030504-1) under Win32,</li>
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<li>GCC 3.3 20030304 (Apple builds 1666 and 1671) under Mac OS,</li>
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<li>GCC 3.3.3 (cygwin special) under Cygwin 1.5.7,</li>
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<li>GCC 3.3.5 under Linux,</li>
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<li>GCC 3.3.6 under Linux and Tru64 (see <a href="#gcc_tru64">below</a>),</li>
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<li>GCC 3.4.2 (mingw-special) under Win32,</li>
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<li>GCC 3.4.3 under Linux, Solaris and Tru64 (see <a href="#gcc_tru64">below</a>),</li>
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<li>GCC 3.4.4 under Linux and Tru64 (see <a href="#gcc_tru64">below</a>),</li>
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<li>GCC 4.0.0 20041026 (Apple build 4061) under Mac OS
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(see <a href="#gcc_4_darwin">below</a>),</li>
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<li>GCC 4.0.0 under Linux,</li>
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<li>GCC 4.0.1 under Linux.</li>
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</ul>
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Boost.MultiIndex does not work with versions 3.1 and prior of GCC.
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</p>
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<h3><a name="gcc_tru64">GNU GCC for Tru64 UNIX</a></h3>
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<p>
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On this platform, GCC is not able to handle debug symbol names whose length
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exceeds 32,768 bytes, resulting in the error <code>mips-tfile, ... string
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too big</code>. You may encounter this issue with heavily templatized
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code like Boost.MultiIndex, which typically produces long symbol names. The problem
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can be overcome by omitting the compiler option <code>-g</code> (generate debugging
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information.) Alternatively, consult the section on
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<a href="#symbol_reduction">reduction of symbol name lengths</a> for various
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applicable workarounds.
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</p>
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<h3><a name="gcc_4_darwin">Darwin GCC 4.0</a></h3>
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<p>
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The build of GCC 4.0 shipped with Darwin 8.1 and prior (Mac OS X 10.4.1 and
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prior) corresponds to a prerelease version of GNU GCC 4.0.0 which introduces
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a <a href="http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17435">regression bug</a>
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related to binding of references to temporary objects. This bug precludes the
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usage of Boost.MultiIndex
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<a href="advanced_topics.html#invariant_check">invariant-checking mode</a>; other
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than this, Boost.MultiIndex works correctly.
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The bug is corrected in the official release of GNU GCC 4.0.0, so the
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invariant-checking mode will be available again once Darwin upgrades to
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a newer version of GCC 4.0.
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</p>
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<h2><a name="acc_60">HP aC++ A.06.00 for HP-UX</a></h2>
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<p>
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No problems have been detected with this compiler.
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</p>
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<h2><a name="va_60">IBM VisualAge C++ V6.0 for AIX</a></h2>
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<p>
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<a href="reference/key_extraction.html#member"><code>member</code></a> not supported,
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refer to the section on
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<a href="#member_offset">use of <code>member_offset</code></a> for workarounds.
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<code>member_offset</code> causes the compiler to emit warnings about the
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use of <code>offsetof</code> with non-POD types: these warnings can be suppressed
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by setting the compiler option <code>-qsuppress=1540-1281</code>, or, alternatively,
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by inserting the following preprocessor directive:
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</p>
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<blockquote><pre>
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<span class=preprocessor>#pragma</span> <span class=identifier>info</span><span class=special>(</span><span class=identifier>nolan</span><span class=special>)</span>
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</pre></blockquote>
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<p>
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This latter pragma, however, may also eliminate other warnings not related
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to the use of <code>offsetof</code>.
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</p>
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<blockquote><hr></blockquote>
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<p>
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Serialization capabilities are not available as Boost.Serialization is not
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supported on this platform.
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</p>
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<h2><a name="intel_71_8x_lin">Intel C++ Compiler for Linux 7.1/8.0/8.1</a></h2>
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<p>
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No problems have been detected with these compilers.
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</p>
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<h2><a name="intel_em64t_81_lin">Intel C++ Compiler Extended Memory 64 Technology 8.1
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for Linux</a></h2>
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<p>
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No problems have been detected with this compiler.
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</p>
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<h2><a name="intel_7x_win">Intel C++ Compiler for Windows 32-bit 7.0/7.1</a></h2>
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<p>
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<a href="reference/key_extraction.html#member"><code>member</code></a> not supported,
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refer to the section on
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<a href="#member_offset">use of <code>member_offset</code></a> for workarounds.
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</p>
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<blockquote><hr></blockquote>
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<p>
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When used on top of MSVC++ 7.0 or prior, argument dependent lookup is
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disabled by default. This will cause problems with many Boost libraries,
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and in particular with the serialization part of Boost.MultiIndex.
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Argument dependent lookup is enabled by adding
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<code>/Qoption,c,--arg_dep_lookup</code> to the project options.
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</p>
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<h2><a name="#intel_71_win_stlport_453">
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Intel C++ Compiler for Windows 32-bit 7.1 + STLport 4.5.3</a></h2>
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<p>
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Boost.MultiIndex works for this configuration. The same limitations apply as
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in Intel C++ 7.1 with its original Dinkumware standard library. STLport 4.6.2 has
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also been confirmed to work correctly.
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</p>
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<h2><a name="intel_8x_9x_win">Intel C++ Compiler for Windows 32-bit 8.0/8.1/9.0</a></h2>
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<p>
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When used on top of MSVC++ 7.0 or prior, argument dependent lookup is
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disabled by default. This will cause problems with many Boost libraries,
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and in particular with the serialization part of Boost.MultiIndex.
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Argument dependent lookup is enabled by adding
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<code>/Qoption,c,--arg_dep_lookup</code> to the project options.
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Other than this, Boost.MultiIndex works without problems.
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</p>
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<h2><a name="cw_83_9x">Metrowerks CodeWarrior 8.3 and later</a></h2>
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<p>
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Boost.MultiIndex works correctly with versions of this compiler from 8.3 to
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9.5, under the two operating systems tested: Mac OS and Windows.
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</p>
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<h2><a name="msvc_60">Microsoft Visual C++ 6.0 Service Pack 5</a></h2>
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<p>
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<a href="reference/key_extraction.html#member"><code>member</code></a> not supported,
|
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refer to the section on
|
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<a href="#member_offset">use of <code>member_offset</code></a> for workarounds.
|
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</p>
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<p>
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<a href="reference/key_extraction.html#const_mem_fun"><code>const_mem_fun</code></a> and
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<a href="reference/key_extraction.html#mem_fun"><code>mem_fun</code></a>
|
|
not supported, refer to the section on
|
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<a href="#mem_fun_explicit">use of <code>const_mem_fun_explicit</code> and
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<code>mem_fun_explicit</code></a> for workarounds.
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</p>
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<blockquote><hr></blockquote>
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<p>
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No support for <a href="reference/multi_index_container.html#index_retrieval">index retrieval</a>
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and <a href="reference/multi_index_container.html#projection">projection</a>
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nested types and member functions:
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<ul>
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<li><code>nth_index</code>,</li>
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<li><code>index</code>,</li>
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<li><code>nth_index_iterator</code>,</li>
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<li><code>nth_index_const_iterator</code>,</li>
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<li><code>index_iterator</code>,</li>
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<li><code>index_const_iterator</code>,</li>
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<li><code>get</code>,</li>
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<li><code>project</code>.</li>
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</ul>
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You can use instead their global equivalents. Also, this compiler does not
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implement argument dependent lookup, so you might need to explicitly qualify
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these global names with <code>::boost::multi_index</code>.
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</p>
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<blockquote><hr></blockquote>
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<p>
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<code>boost::multi_index::multi_index_container</code> is imported to
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<code>namespace boost</code> by means of a <code>using</code> declaration.
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MSVC++ 6.0, however, does not properly handle this import. So, instead of
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writing:
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</p>
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<blockquote><pre>
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<span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index_container</span><span class=special><...></span>
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</pre></blockquote>
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<p>
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use the following:
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</p>
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<blockquote><pre>
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<span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>multi_index_container</span><span class=special><...></span>
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</pre></blockquote>
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<p>
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or else resort to a directive <code>using namespace boost::multi_index</code>.
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</p>
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<blockquote><hr></blockquote>
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<p>
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The lack of partial template specialization support in MSVC++ 6.0
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results in some inconveniences when using <code>composite_key</code> that
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can be remedied as explained in
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<a href="#composite_key_no_pts">"<code>composite_key</code>
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in compilers without partial template specialization"</a>.
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</p>
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<blockquote><hr></blockquote>
|
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<p>
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MSVC++ 6.0 presents serious limitations for the maximum length of
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symbol names generated by the compiler, which might result in the
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linker error
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<code><a href="http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vccore98/html/lnk1179.asp">LNK1179</a>:
|
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invalid or corrupt file: duplicate comdat
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comdat</code>. To overcome this problem, consult the section on
|
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<a href="#symbol_reduction">reduction of symbol name lengths</a> for various
|
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applicable workarounds.
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</p>
|
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|
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<blockquote><hr></blockquote>
|
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|
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<p>
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Under some circumstances, the compiler emits the error
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<a href="http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vccore98/html/C2587.asp">
|
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<code>C2587</code></a><code>: '_U' : illegal use of local variable as
|
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default parameter</code>, inside the MSVC internal header
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<code><xlocnum></code>.
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This problem is a recurrent bug of the compiler, and has been reported in
|
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other unrelated libraries, like the
|
|
<a href="../../../libs/graph/doc/table_of_contents.html">Boost Graph Library</a>,
|
|
<a href="../../../libs/multi_array/doc/index.html">Boost.MultiArray</a>,
|
|
<a href="../../../libs/regex/doc/index.html">Boost.Regex</a>,
|
|
<a href="http://www.cgal.org/">CGAL</a> and
|
|
<a href="http://www.mysql.com/downloads/api-mysql++.html">MySQL++</a>.
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|
The error is triggered, though not in a systematic manner, by the use
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of <code>multi_index_container</code> iterator constructor. Two workarounds exist:
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the first consists of avoiding this constructor and replacing
|
|
code like:
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|
</p>
|
|
|
|
<blockquote><pre>
|
|
<span class=identifier>multi_index_container</span><span class=special><...></span> <span class=identifier>s</span><span class=special>(</span><span class=identifier>c</span><span class=special>.</span><span class=identifier>begin</span><span class=special>(),</span><span class=identifier>c</span><span class=special>.</span><span class=identifier>end</span><span class=special>());</span>
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</pre></blockquote>
|
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|
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<p>
|
|
with equivalent operations:
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</p>
|
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|
|
<blockquote><pre>
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|
<span class=identifier>multi_index_container</span><span class=special><...></span> <span class=identifier>s</span><span class=special>;</span>
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<span class=identifier>s</span><span class=special>.</span><span class=identifier>insert</span><span class=special>(</span><span class=identifier>c</span><span class=special>.</span><span class=identifier>begin</span><span class=special>(),</span><span class=identifier>c</span><span class=special>.</span><span class=identifier>end</span><span class=special>());</span>
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</pre></blockquote>
|
|
|
|
<p>
|
|
The second workaround has not been confirmed by the author, but it is given
|
|
on the Internet in connection with this error appearing in other libraries.
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|
Replace line 84 of <code><xlocnum></code>
|
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|
|
<blockquote><pre>
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|
<span class=preprocessor>#define</span> <span class=identifier>_VIRTUAL</span> <span class=keyword>virtual</span>
|
|
</pre></blockquote>
|
|
|
|
<p>
|
|
with the following:
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|
</p>
|
|
|
|
<blockquote><pre>
|
|
<span class=preprocessor>#define</span> <span class=identifier>_VIRTUAL</span>
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</pre></blockquote>
|
|
|
|
<p>
|
|
<b>Warning</b>: it is not known whether this
|
|
replacement can result in unexpected side effects in code implicitly
|
|
using <code><xlocnum></code>.
|
|
</p>
|
|
|
|
<blockquote><hr></blockquote>
|
|
|
|
<p>
|
|
In general, the extensive use of templates by Boost.MultiIndex puts this compiler
|
|
under severe stress, so that several internal limitations may be reached.
|
|
The following measures can help alleviate these problems:
|
|
<ul>
|
|
<li>Set the compiler option <code>/Zm</code> (Specify Memory Allocation Limit)
|
|
to increase the amount of memory available for compilation. Usual values for
|
|
this option range from 300 to 800.</li>
|
|
<li>If in debug mode, try switching from <code>/ZI</code> (Program Database for
|
|
Edit and Continue) to a less demanding type of debugging information
|
|
(<code>/Zi</code>, <code>/Z7</code> or <code>/Zd</code>.)</li>
|
|
<li>Play with the precompiled headers options. Usually, turning this feature
|
|
off yields the best results.</li>
|
|
<li>If the compiler emits the error
|
|
<a href="http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vccore98/html/c1055.asp">
|
|
<code>C1055</code></a><code>: compiler limit : out of keys</code>, try
|
|
disabling the option <code>/Gm</code> (Enable Minimal Rebuild.) In these
|
|
cases, it is also beneficial to split the project into smaller
|
|
subprojects.</li>
|
|
</ul>
|
|
</p>
|
|
|
|
<h2>
|
|
<a name="msvc_60_stlport_453">Microsoft Visual C++ 6.0 Service Pack 5
|
|
+ STLport 4.5.3</a>
|
|
</h2>
|
|
|
|
<p>
|
|
Boost.MultiIndex works for this configuration. The same limitations apply as
|
|
in MSVC++ 6.0 with its original Dinkumware standard library. STLport 4.6.2 has
|
|
also been confirmed to work correctly.
|
|
</p>
|
|
|
|
<blockquote><hr></blockquote>
|
|
|
|
<p>
|
|
It is not possible to use the serialization capabilities of Boost.MultiIndex
|
|
along with the dynamic version of STLport, as some linking errors result.
|
|
Use instead the static version of STLport. This bug is reportedly fixed in
|
|
STLport 5.0 (in beta stage as of this writing.)
|
|
</p>
|
|
|
|
<h2><a name="msvc_70">Microsoft Visual C++ 7.0</a></h2>
|
|
|
|
<p>
|
|
<a href="reference/key_extraction.html#member"><code>member</code></a> not supported,
|
|
refer to the section on
|
|
<a href="#member_offset">use of <code>member_offset</code></a> for workarounds.
|
|
</p>
|
|
|
|
<blockquote><hr></blockquote>
|
|
|
|
<p>
|
|
No support for <a href="reference/multi_index_container.html#index_retrieval">index retrieval</a>
|
|
and <a href="reference/multi_index_container.html#projection">projection</a>
|
|
nested types and member functions:
|
|
<ul>
|
|
<li><code>nth_index</code>,</li>
|
|
<li><code>index</code>,</li>
|
|
<li><code>nth_index_iterator</code>,</li>
|
|
<li><code>nth_index_const_iterator</code>,</li>
|
|
<li><code>index_iterator</code>,</li>
|
|
<li><code>index_const_iterator</code>,</li>
|
|
<li><code>get</code>,</li>
|
|
<li><code>project</code>.</li>
|
|
</ul>
|
|
You can use instead their global equivalents. Also, this compiler does not
|
|
implement argument dependent lookup, so you might need to explicitly qualify
|
|
these global names with <code>::boost::multi_index</code>.
|
|
</p>
|
|
|
|
<blockquote><hr></blockquote>
|
|
|
|
<p>
|
|
<code>boost::multi_index::multi_index_container</code> is imported to
|
|
<code>namespace boost</code> by means of a <code>using</code> declaration.
|
|
MSVC++ 7.0, however, does not properly handle this import. So, instead of
|
|
writing:
|
|
</p>
|
|
|
|
<blockquote><pre>
|
|
<span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index_container</span><span class=special><...></span>
|
|
</pre></blockquote>
|
|
|
|
<p>
|
|
use the following:
|
|
</p>
|
|
|
|
<blockquote><pre>
|
|
<span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>multi_index_container</span><span class=special><...></span>
|
|
</pre></blockquote>
|
|
|
|
<p>
|
|
or else resort to a directive <code>using namespace boost::multi_index</code>.
|
|
</p>
|
|
|
|
<blockquote><hr></blockquote>
|
|
|
|
<p>
|
|
The lack of partial template specialization support in MSVC++ 7.0
|
|
results in some inconveniences when using <code>composite_key</code> that
|
|
can be remedied as explained in
|
|
<a href="#composite_key_no_pts">"<code>composite_key</code>
|
|
in compilers without partial template specialization"</a>.
|
|
</p>
|
|
|
|
<h2><a name="msvc_71">Microsoft Visual C++ 7.1</a></h2>
|
|
|
|
<p>
|
|
Problems have been reported when compiling the library with the <code>/Gm</code>
|
|
option (Enable Minimal Rebuild.) Seemingly, this is due to an
|
|
internal defect of the compiler (see for instance
|
|
<a href="http://lists.boost.org/MailArchives/boost-users/msg05988.php">
|
|
this mention of a similar issue</a> in the Boost Users mailing list.)
|
|
If <code>/Gm</code> is turned off, Boost.MultiIndex compiles and runs
|
|
without further problems.
|
|
</p>
|
|
|
|
<h2><a name="msvc_80">Microsoft Visual C++ 8.0</a></h2>
|
|
|
|
<p>
|
|
No problems have been detected with this compiler. The Beta 2 version of
|
|
this product was used for the testing.
|
|
</p>
|
|
|
|
<h2><a name="portability">Portability techniques</a></h2>
|
|
|
|
<h3><a name="member_offset">Use of <code>member_offset</code></a></h3>
|
|
|
|
<p>
|
|
The <code>member</code> key extractor poses some problems in compilers
|
|
that do not properly support pointers to members as non-type
|
|
template arguments, as indicated by the
|
|
<a href="../../../libs/config/config.htm">Boost Configuration Library</a>
|
|
defect macro <code>BOOST_NO_POINTER_TO_MEMBER_TEMPLATE_PARAMETERS</code>.
|
|
The following compilers have been confirmed not
|
|
to work correctly with <code>member</code>:
|
|
<ul>
|
|
<li>MSVC++ 6.0/7.0,</li>
|
|
<li>Intel C++ 7.0/7.1 for Windows,</li>
|
|
<li>VisualAge 6.0 for AIX.</li>
|
|
</ul>
|
|
This program can help determine if your compiler
|
|
properly supports pointers to members as non-type template parameters:
|
|
</p>
|
|
|
|
<blockquote><pre>
|
|
<span class=preprocessor>#include</span> <span class=special><</span><span class=identifier>iostream</span><span class=special>></span>
|
|
|
|
<span class=keyword>struct</span> <span class=identifier>pair</span>
|
|
<span class=special>{</span>
|
|
<span class=keyword>int</span> <span class=identifier>x</span><span class=special>,</span><span class=identifier>y</span><span class=special>;</span>
|
|
|
|
<span class=identifier>pair</span><span class=special>(</span><span class=keyword>int</span> <span class=identifier>x_</span><span class=special>,</span><span class=keyword>int</span> <span class=identifier>y_</span><span class=special>):</span><span class=identifier>x</span><span class=special>(</span><span class=identifier>x_</span><span class=special>),</span><span class=identifier>y</span><span class=special>(</span><span class=identifier>y_</span><span class=special>){}</span>
|
|
<span class=special>};</span>
|
|
|
|
<span class=keyword>template</span><span class=special><</span><span class=keyword>int</span> <span class=identifier>pair</span><span class=special>::*</span> <span class=identifier>PtrToPairMember</span><span class=special>></span>
|
|
<span class=keyword>struct</span> <span class=identifier>foo</span>
|
|
<span class=special>{</span>
|
|
<span class=keyword>int</span> <span class=identifier>bar</span><span class=special>(</span><span class=identifier>pair</span><span class=special>&</span> <span class=identifier>p</span><span class=special>){</span><span class=keyword>return</span> <span class=identifier>p</span><span class=special>.*</span><span class=identifier>PtrToPairMember</span><span class=special>;}</span>
|
|
<span class=special>};</span>
|
|
|
|
<span class=keyword>int</span> <span class=identifier>main</span><span class=special>()</span>
|
|
<span class=special>{</span>
|
|
<span class=identifier>pair</span> <span class=identifier>p</span><span class=special>(</span><span class=number>0</span><span class=special>,</span><span class=number>1</span><span class=special>);</span>
|
|
<span class=identifier>foo</span><span class=special><&</span><span class=identifier>pair</span><span class=special>::</span><span class=identifier>x</span><span class=special>></span> <span class=identifier>fx</span><span class=special>;</span>
|
|
<span class=identifier>foo</span><span class=special><&</span><span class=identifier>pair</span><span class=special>::</span><span class=identifier>y</span><span class=special>></span> <span class=identifier>fy</span><span class=special>;</span>
|
|
|
|
<span class=keyword>if</span><span class=special>(</span><span class=identifier>fx</span><span class=special>.</span><span class=identifier>bar</span><span class=special>(</span><span class=identifier>p</span><span class=special>)!=</span><span class=number>0</span><span class=special>||</span><span class=identifier>fy</span><span class=special>.</span><span class=identifier>bar</span><span class=special>(</span><span class=identifier>p</span><span class=special>)!=</span><span class=number>1</span><span class=special>)</span><span class=identifier>std</span><span class=special>::</span><span class=identifier>cout</span><span class=special><<</span><span class=string>"KO"</span><span class=special><<</span><span class=identifier>std</span><span class=special>::</span><span class=identifier>endl</span><span class=special>;</span>
|
|
<span class=keyword>else</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>cout</span><span class=special><<</span><span class=string>"OK"</span><span class=special><<</span><span class=identifier>std</span><span class=special>::</span><span class=identifier>endl</span><span class=special>;</span>
|
|
|
|
<span class=keyword>return</span> <span class=number>0</span><span class=special>;</span>
|
|
<span class=special>}</span>
|
|
|
|
</pre></blockquote>
|
|
|
|
<p>
|
|
If you find a compiler that does not pass the test, and for which
|
|
<code>BOOST_NO_POINTER_TO_MEMBER_TEMPLATE_PARAMETERS</code> is <i>not</i> defined,
|
|
please report to the Boost developers mailing list.
|
|
</p>
|
|
<p>To overcome this defect, a replacement utility
|
|
<a href="reference/key_extraction.html#member_offset"><code>member_offset</code></a>
|
|
has been provided that does the work of <code>member</code> at the
|
|
expense of less convenient notation and the possibility of
|
|
non-conformance with the standard. Please consult
|
|
the reference for further information on <code>member_offset</code>.
|
|
As an example of use, given the class
|
|
</p>
|
|
|
|
<blockquote><pre>
|
|
<span class=keyword>class</span> <span class=identifier>A</span>
|
|
<span class=special>{</span>
|
|
<span class=keyword>int</span> <span class=identifier>x</span><span class=special>;</span>
|
|
<span class=special>}</span>
|
|
</pre></blockquote>
|
|
|
|
<p>
|
|
the instantiation <code>member<A,int,&A::x></code> can be simulated then
|
|
as <code>member_offset<A,int,offsetof(A,x)></code>.
|
|
</p>
|
|
|
|
<p>
|
|
For those writing portable code, Boost.MultiIndex provides the ternary macro
|
|
<a href="reference/key_extraction.html#boost_multi_index_member"><code>BOOST_MULTI_INDEX_MEMBER</code></a>.
|
|
Continuing with the example above, the
|
|
expression
|
|
</p>
|
|
|
|
<blockquote><pre>
|
|
<span class=identifier>BOOST_MULTI_INDEX_MEMBER</span><span class=special>(</span><span class=identifier>A</span><span class=special>,</span><span class=keyword>int</span><span class=special>,</span><span class=identifier>x</span><span class=special>)</span>
|
|
</pre></blockquote>
|
|
|
|
<p>
|
|
expands by default to
|
|
</p>
|
|
|
|
<blockquote><pre>
|
|
<span class=identifier>member</span><span class=special><</span><span class=identifier>A</span><span class=special>,</span><span class=keyword>int</span><span class=special>,&</span><span class=identifier>A</span><span class=special>::</span><span class=identifier>x</span><span class=special>></span>
|
|
</pre></blockquote>
|
|
|
|
<p>
|
|
or alternatively to
|
|
</p>
|
|
|
|
<blockquote><pre>
|
|
<span class=identifier>member_offset</span><span class=special><</span><span class=identifier>A</span><span class=special>,</span><span class=keyword>int</span><span class=special>,</span><span class=identifier>offsetof</span><span class=special>(</span><span class=identifier>A</span><span class=special>,</span><span class=identifier>x</span><span class=special>)></span>
|
|
</pre></blockquote>
|
|
|
|
<p>
|
|
if <code>BOOST_NO_POINTER_TO_MEMBER_TEMPLATE_PARAMETERS</code> is defined.
|
|
</p>
|
|
|
|
<h3><a name="mem_fun_explicit">Use of <code>const_mem_fun_explicit</code> and
|
|
<code>mem_fun_explicit</code></a></h3>
|
|
|
|
<p>
|
|
MSVC++ 6.0 has problems with <code>const</code> member functions as non-type
|
|
template parameters, and thus does not accept the <code>const_mem_fun</code>
|
|
key extractor. A simple workaround, fortunately, has been found, consisting
|
|
in specifying the <i>type</i> of these pointers as an additional template
|
|
parameter. The alternative
|
|
<a href="reference/key_extraction.html#const_mem_fun_explicit"><code>const_mem_fun_explicit</code></a>
|
|
extractor adopts this solution; for instance, given the type
|
|
</p>
|
|
|
|
<blockquote><pre>
|
|
<span class=keyword>struct</span> <span class=identifier>A</span>
|
|
<span class=special>{</span>
|
|
<span class=keyword>int</span> <span class=identifier>f</span><span class=special>()</span><span class=keyword>const</span><span class=special>;</span>
|
|
<span class=special>};</span>
|
|
</pre></blockquote>
|
|
|
|
<p>
|
|
the extractor <code>const_mem_fun<A,int,&A::f></code> can be replaced by
|
|
<code>const_mem_fun_explicit<A,int,int (A::*)()const,&A::f></code>. A similar
|
|
<code>mem_fun_explicit</code> class template is provided for non-constant
|
|
member functions.
|
|
</p>
|
|
|
|
<p>
|
|
If you are writing cross-platform code, the selection of either key extractor
|
|
is transparently handled by the macro
|
|
<a href="reference/key_extraction.html#boost_multi_index_const_mem_fun"><code>BOOST_MULTI_INDEX_CONST_MEM_FUN</code></a>,
|
|
so that
|
|
</p>
|
|
|
|
<blockquote><pre>
|
|
<span class=identifier>BOOST_MULTI_INDEX_CONST_MEM_FUN</span><span class=special>(</span><span class=identifier>A</span><span class=special>,</span><span class=keyword>int</span><span class=special>,</span><span class=identifier>f</span><span class=special>)</span>
|
|
</pre></blockquote>
|
|
|
|
<p>
|
|
expands by default to
|
|
</p>
|
|
|
|
<blockquote><pre>
|
|
<span class=identifier>const_mem_fun</span><span class=special><</span><span class=identifier>A</span><span class=special>,</span><span class=keyword>int</span><span class=special>,&</span><span class=identifier>A</span><span class=special>::</span><span class=identifier>f</span><span class=special>></span>
|
|
</pre></blockquote>
|
|
|
|
<p>
|
|
but resolves to
|
|
</p>
|
|
|
|
<blockquote><pre>
|
|
<span class=identifier>const_mem_fun_explicit</span><span class=special><</span><span class=identifier>A</span><span class=special>,</span><span class=keyword>int</span><span class=special>,</span><span class=keyword>int</span> <span class=special>(</span><span class=identifier>A</span><span class=special>::*)()</span><span class=keyword>const</span><span class=special>,&</span><span class=identifier>A</span><span class=special>::</span><span class=identifier>f</span><span class=special>></span>
|
|
</pre></blockquote>
|
|
|
|
<p>
|
|
in MSVC++ 6.0. Non-<code>const</code> member functions are covered by
|
|
<a href="reference/key_extraction.html#mem_fun_explicit"><code>mem_fun_explicit</code></a>
|
|
and the macro
|
|
<a href="reference/key_extraction.html#boost_multi_index_mem_fun"><code>BOOST_MULTI_INDEX_MEM_FUN</code></a>.
|
|
</p>
|
|
|
|
<h3><a name="composite_key_no_pts"><code>composite_key</code> in compilers
|
|
without partial template specialization</a></h3>
|
|
|
|
<p>
|
|
When using <code>composite_key</code>s, lookup is performed by passing
|
|
tuples of values: this ability is achieved by suitably specializing
|
|
the class templates <code>std::equal_to</code>, <code>std::less</code>,
|
|
<code>std::greater</code> and <code>boost::hash</code> for
|
|
<a href="reference/key_extraction.html#composite_key_result">
|
|
<code>composite_key_result</code></a> instantiations so that they
|
|
provide the appropriate overloads accepting tuples --and in the case
|
|
of <code>std::less</code> and <code>std::greater</code>, also partial
|
|
tuples where only the first components are specified.
|
|
</p>
|
|
|
|
<p>
|
|
In those compilers that do not support partial template specialization,
|
|
these specializations cannot be provided, and so
|
|
tuple-based lookup is not available by default. In this case,
|
|
<code>multi_index_container</code> instantiations using composite keys
|
|
will work as expected, both for ordered and hashed indices,
|
|
except that lookup operations will not accept tuples as an argument.
|
|
For ordered indices, the most obvious workaround
|
|
to this deficiency involves explicitly specifying the comparison
|
|
predicate with
|
|
<a href="reference/key_extraction.html#composite_key_compare"><code>composite_key_compare</code></a>;
|
|
in the case of hashed indices we can use the analogous
|
|
<a href="reference/key_extraction.html#composite_key_equal_to"><code>composite_key_equal_to</code></a>
|
|
and
|
|
<a href="reference/key_extraction.html#composite_key_hash"><code>composite_key_hash</code></a>.
|
|
This substitution is tedious as the elementary components for all the constituent key extractors must
|
|
be explicitly typed. For this reason, Boost.MultiIndex provides the following replacement
|
|
class templates
|
|
<ul>
|
|
<li><a href="reference/key_extraction.html#composite_key_result_equal_to">
|
|
<code>composite_key_result_equal_to</code></a>,</li>
|
|
<li><a href="reference/key_extraction.html#composite_key_result_less">
|
|
<code>composite_key_result_less</code></a>,</li>
|
|
<li><a href="reference/key_extraction.html#composite_key_result_greater">
|
|
<code>composite_key_result_greater</code></a> and</li>
|
|
<li><a href="reference/key_extraction.html#composite_key_result_hash">
|
|
<code>composite_key_result_hash</code></a>,</li>
|
|
</ul>
|
|
that act as the missing specializations of <code>std::equal_to</code>, <code>std::less</code>,
|
|
<code>std::greater</code> and <code>boost::hash</code> for <code>composite_key_result</code>s.
|
|
They can be used as follows:
|
|
</p>
|
|
|
|
<blockquote><pre>
|
|
<span class=keyword>typedef</span> <span class=identifier>composite_key</span><span class=special><</span>
|
|
<span class=identifier>phonebook_entry</span><span class=special>,</span>
|
|
<span class=identifier>member</span><span class=special><</span><span class=identifier>phonebook_entry</span><span class=special>,</span><span class=identifier>std</span><span class=special>::</span><span class=identifier>string</span><span class=special>,&</span><span class=identifier>phonebook_entry</span><span class=special>::</span><span class=identifier>family_name</span><span class=special>>,</span>
|
|
<span class=identifier>member</span><span class=special><</span><span class=identifier>phonebook_entry</span><span class=special>,</span><span class=identifier>std</span><span class=special>::</span><span class=identifier>string</span><span class=special>,&</span><span class=identifier>phonebook_entry</span><span class=special>::</span><span class=identifier>given_name</span><span class=special>></span>
|
|
<span class=special>></span> <span class=identifier>ckey_t</span><span class=special>;</span>
|
|
|
|
<span class=keyword>typedef</span> <span class=identifier>multi_index_container</span><span class=special><</span>
|
|
<span class=identifier>phonebook_entry</span><span class=special>,</span>
|
|
<span class=identifier>indexed_by</span><span class=special><</span>
|
|
<span class=identifier>ordered_non_unique</span><span class=special><</span>
|
|
<span class=identifier>ckey_t</span><span class=special>,</span>
|
|
<span class=comment>// composite_key_result_less plays the role of
|
|
// std::less<ckey_t::result_type></span>
|
|
<span class=identifier>composite_key_result_less</span><span class=special><</span><span class=identifier>ckey_t</span><span class=special>::</span><span class=identifier>result_type</span><span class=special>></span>
|
|
<span class=special>>,</span>
|
|
<span class=identifier>ordered_unique</span><span class=special><</span>
|
|
<span class=identifier>member</span><span class=special><</span><span class=identifier>phonebook_entry</span><span class=special>,</span><span class=identifier>std</span><span class=special>::</span><span class=identifier>string</span><span class=special>,&</span><span class=identifier>phonebook_entry</span><span class=special>::</span><span class=identifier>phone_number</span><span class=special>></span>
|
|
<span class=special>></span>
|
|
<span class=special>></span>
|
|
<span class=special>></span> <span class=identifier>phonebook</span><span class=special>;</span>
|
|
</pre></blockquote>
|
|
|
|
<h3><a name="symbol_reduction">Reduction of symbol name lengths</a></h3>
|
|
|
|
<p>
|
|
The types generated on the instantiations of <code>multi_index_container</code>s
|
|
typically produce very long symbol names, sometimes beyond the internal limits
|
|
of some compilers. There are several techniques to shorten generated symbol
|
|
names: these techniques have also the beneficial side effect that resulting error
|
|
messages are more readable.
|
|
</p>
|
|
|
|
<h4><a name="argument_limitation">Limitation of maximum number of arguments</a></h4>
|
|
|
|
<p>
|
|
The class templates <a href="reference/indices.html#indexed_by"><code>indexed_by</code></a>,
|
|
<a href="reference/indices.html#tag"><code>tag</code></a> and
|
|
<a href="reference/key_extraction.html#composite_key"><code>composite_key</code></a>
|
|
accept a variable number of arguments whose maximum number is limited by
|
|
internal macros. Even non-used arguments contribute to the final types,
|
|
so manually adjusting the corresponding macros can result in a modest reduction
|
|
of symbol names.
|
|
</p>
|
|
|
|
<p align="center">
|
|
<table cellspacing="0">
|
|
<caption><b>Limiting maximum number of arguments of some class templates
|
|
of Boost.MultiIndex.</b></caption>
|
|
<tr>
|
|
<th>class template</th>
|
|
<th>limiting macro</th>
|
|
<th>default value</th>
|
|
<th>default value<br>(MSVC++ 6.0)</th>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"> <code>indexed_by</code> </td>
|
|
<td align="center"> <code>BOOST_MULTI_INDEX_LIMIT_INDEXED_BY_SIZE</code> </td>
|
|
<td align="center">20</td>
|
|
<td align="center">5</td>
|
|
</tr>
|
|
<tr class="odd_tr">
|
|
<td align="center"> <code>tag</code> </td>
|
|
<td align="center"> <code>BOOST_MULTI_INDEX_LIMIT_TAG_SIZE</code> </td>
|
|
<td align="center">20</td>
|
|
<td align="center">3</td>
|
|
</tr>
|
|
<tr>
|
|
<td align="center"> <code>composite_key</code> </td>
|
|
<td align="center"> <code>BOOST_MULTI_INDEX_LIMIT_COMPOSITE_KEY_SIZE</code> </td>
|
|
<td align="center">10</td>
|
|
<td align="center">5</td>
|
|
</tr>
|
|
</table>
|
|
</p>
|
|
|
|
<h4><a name="type_hiding">Type hiding</a></h4>
|
|
|
|
<p>
|
|
Consider a typical instantiation of <code>multi_index_container</code>:
|
|
</p>
|
|
|
|
<blockquote><pre>
|
|
<span class=keyword>typedef</span> <span class=identifier>multi_index_container</span><span class=special><</span>
|
|
<span class=identifier>employee</span><span class=special>,</span>
|
|
<span class=identifier>indexed_by</span><span class=special><</span>
|
|
<span class=identifier>ordered_unique</span><span class=special><</span><span class=identifier>identity</span><span class=special><</span><span class=identifier>employee</span><span class=special>></span> <span class=special>>,</span>
|
|
<span class=identifier>ordered_non_unique</span><span class=special><</span><span class=identifier>member</span><span class=special><</span><span class=identifier>employee</span><span class=special>,</span><span class=identifier>std</span><span class=special>::</span><span class=identifier>string</span><span class=special>,&</span><span class=identifier>employee</span><span class=special>::</span><span class=identifier>name</span><span class=special>></span> <span class=special>>,</span>
|
|
<span class=identifier>ordered_unique</span><span class=special><</span><span class=identifier>member</span><span class=special><</span><span class=identifier>employee</span><span class=special>,</span><span class=keyword>int</span><span class=special>,&</span><span class=identifier>employee</span><span class=special>::</span><span class=identifier>ssnumber</span><span class=special>></span> <span class=special>></span>
|
|
<span class=special>></span>
|
|
<span class=special>></span> <span class=identifier>employee_set</span><span class=special>;</span>
|
|
</pre></blockquote>
|
|
|
|
<p>
|
|
Then, for instance, the type <code>employee_set::nth_type<0>::type</code>
|
|
resolves to the following in GCC:
|
|
</p>
|
|
|
|
<blockquote><pre>
|
|
<span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>detail</span><span class=special>::</span><span class=identifier>ordered_index</span><span class=special><</span>
|
|
<span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>identity</span><span class=special><</span><span class=identifier>employee</span><span class=special>>,</span>
|
|
<span class=identifier>std</span><span class=special>::</span><span class=identifier>less</span><span class=special><</span><span class=identifier>employee</span><span class=special>>,</span>
|
|
<span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>detail</span><span class=special>::</span><span class=identifier>nth_layer</span><span class=special><</span>
|
|
<span class=number>1</span><span class=special>,</span> <span class=identifier>employee</span><span class=special>,</span>
|
|
<span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>indexed_by</span><span class=special><</span>
|
|
<span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>ordered_unique</span><span class=special><</span>
|
|
<span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>identity</span><span class=special><</span><span class=identifier>employee</span><span class=special>>,</span> <span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>,</span> <span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span>
|
|
<span class=special>>,</span>
|
|
<span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>ordered_non_unique</span><span class=special><</span>
|
|
<span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>member</span><span class=special><</span><span class=identifier>employee</span><span class=special>,</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>string</span><span class=special>,</span> <span class=special>&</span><span class=identifier>employee</span><span class=special>::</span><span class=identifier>name</span><span class=special>>,</span>
|
|
<span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>,</span> <span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span>
|
|
<span class=special>>,</span>
|
|
<span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>ordered_unique</span><span class=special><</span>
|
|
<span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>member</span><span class=special><</span><span class=identifier>employee</span><span class=special>,</span> <span class=keyword>int</span><span class=special>,</span> <span class=special>&</span><span class=identifier>employee</span><span class=special>::</span><span class=identifier>ssnumber</span><span class=special>>,</span>
|
|
<span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>,</span> <span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span>
|
|
<span class=special>>,</span>
|
|
<span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>,</span> <span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>,</span> <span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>,</span> <span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>,</span> <span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>,</span> <span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>,</span>
|
|
<span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>,</span> <span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>,</span> <span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>,</span> <span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>,</span> <span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>,</span> <span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>,</span>
|
|
<span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>,</span> <span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>,</span> <span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>,</span> <span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>,</span> <span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span>
|
|
<span class=special>>,</span>
|
|
<span class=identifier>std</span><span class=special>::</span><span class=identifier>allocator</span><span class=special><</span><span class=identifier>employee</span><span class=special>></span>
|
|
<span class=special>>,</span>
|
|
<span class=identifier>boost</span><span class=special>::</span><span class=identifier>mpl</span><span class=special>::</span><span class=identifier>vector0</span><span class=special><</span><span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>>,</span>
|
|
<span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>detail</span><span class=special>::</span><span class=identifier>ordered_unique_tag</span>
|
|
<span class=special>></span>
|
|
</pre></blockquote>
|
|
|
|
<p>
|
|
It can be seen that a significant portion of the type name is contributed by
|
|
the <code>indexed_by<...></code> part, which is nothing but an expanded
|
|
version of the index specifier list provided in the definition of
|
|
<code>employee_set</code>. We can prevent this very long name from appearing
|
|
in the final type by encapsulating it into another, shorter-named construct:
|
|
</p>
|
|
|
|
<blockquote><pre>
|
|
<span class=comment>// reducing symbol names through type hiding
|
|
// type hide the index spexifier list within employee_set_indices</span>
|
|
|
|
<span class=keyword>struct</span> <span class=identifier>employee_set_indices</span><span class=special>:</span>
|
|
<span class=identifier>indexed_by</span><span class=special><</span>
|
|
<span class=identifier>ordered_unique</span><span class=special><</span><span class=identifier>identity</span><span class=special><</span><span class=identifier>employee</span><span class=special>></span> <span class=special>>,</span>
|
|
<span class=identifier>ordered_non_unique</span><span class=special><</span><span class=identifier>member</span><span class=special><</span><span class=identifier>employee</span><span class=special>,</span><span class=identifier>std</span><span class=special>::</span><span class=identifier>string</span><span class=special>,&</span><span class=identifier>employee</span><span class=special>::</span><span class=identifier>name</span><span class=special>></span> <span class=special>>,</span>
|
|
<span class=identifier>ordered_unique</span><span class=special><</span><span class=identifier>member</span><span class=special><</span><span class=identifier>employee</span><span class=special>,</span><span class=keyword>int</span><span class=special>,&</span><span class=identifier>employee</span><span class=special>::</span><span class=identifier>ssnumber</span><span class=special>></span> <span class=special>></span>
|
|
<span class=special>></span>
|
|
<span class=special>{};</span>
|
|
|
|
<span class=keyword>typedef</span> <span class=identifier>multi_index_container</span><span class=special><</span>
|
|
<span class=identifier>employee</span><span class=special>,</span>
|
|
<span class=identifier>employee_set_indices</span>
|
|
<span class=special>></span> <span class=identifier>employee_set</span><span class=special>;</span>
|
|
</pre></blockquote>
|
|
|
|
<p>
|
|
<code>employee_set_indices</code> works as a conventional <code>typedef</code>
|
|
in all respects, save for a detail: its name does not explicitly
|
|
include the information contained in the <code>indexed_by</code> instantiation.
|
|
Applying this technique, <code>employee_set::nth_type<0>::type</code>
|
|
now becomes:
|
|
</p>
|
|
|
|
<blockquote><pre>
|
|
<span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>detail</span><span class=special>::</span><span class=identifier>ordered_index</span><span class=special><</span>
|
|
<span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>identity</span><span class=special><</span><span class=identifier>employee</span><span class=special>>,</span>
|
|
<span class=identifier>std</span><span class=special>::</span><span class=identifier>less</span><span class=special><</span><span class=identifier>employee</span><span class=special>>,</span>
|
|
<span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>detail</span><span class=special>::</span><span class=identifier>nth_layer</span><span class=special><</span>
|
|
<span class=number>1</span><span class=special>,</span> <span class=identifier>employee</span><span class=special>,</span>
|
|
<span class=identifier>employee_set_indices</span><span class=special>,</span>
|
|
<span class=identifier>std</span><span class=special>::</span><span class=identifier>allocator</span><span class=special><</span><span class=identifier>employee</span><span class=special>></span>
|
|
<span class=special>>,</span>
|
|
<span class=identifier>boost</span><span class=special>::</span><span class=identifier>mpl</span><span class=special>::</span><span class=identifier>vector0</span><span class=special><</span><span class=identifier>mpl_</span><span class=special>::</span><span class=identifier>na</span><span class=special>>,</span>
|
|
<span class=identifier>boost</span><span class=special>::</span><span class=identifier>multi_index</span><span class=special>::</span><span class=identifier>detail</span><span class=special>::</span><span class=identifier>ordered_unique_tag</span>
|
|
<span class=special>></span>
|
|
</pre></blockquote>
|
|
|
|
<p>
|
|
which is considerably shorter than the original, and also more
|
|
easily parsed by a human reader. Type hiding would not work if, instead of
|
|
making <code>employee_set_indices</code> a derived <code>struct</code> of
|
|
<code>indexed_by<...></code>, we had defined it as a <code>typedef</code>:
|
|
<code>typedef</code>s are syntactic aliases and usually get expanded
|
|
by the compiler before doing any further type handling.
|
|
</p>
|
|
|
|
<p>
|
|
Type hiding techniques can also be applied to <code>composite_key</code> intantiations,
|
|
which often contribute a great deal to symbol name lengths.
|
|
</p>
|
|
|
|
<hr>
|
|
|
|
<div class="prev_link"><a href="reference/key_extraction.html"><img src="prev.gif" alt="key extraction" border="0"><br>
|
|
Key extraction
|
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</a></div>
|
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<div class="up_link"><a href="index.html"><img src="up.gif" alt="index" border="0"><br>
|
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Index
|
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</a></div>
|
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<div class="next_link"><a href="performance.html"><img src="next.gif" alt="performance" border="0"><br>
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Performance
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</a></div><br clear="all" style="clear: all;">
|
|
|
|
<br>
|
|
|
|
<p>Revised July 13th 2005</p>
|
|
|
|
<p>© Copyright 2003-2005 Joaquín M López Muñoz.
|
|
Distributed under the Boost Software
|
|
License, Version 1.0. (See accompanying file <a href="../../../LICENSE_1_0.txt">
|
|
LICENSE_1_0.txt</a> or copy at <a href="http://www.boost.org/LICENSE_1_0.txt">
|
|
http://www.boost.org/LICENSE_1_0.txt</a>)
|
|
</p>
|
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</body>
|
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</html>
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