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- <h2><span class="refentrytitle">Macro BOOST_VMD_IDENTITY</span></h2>
- <p>BOOST_VMD_IDENTITY — Macro which expands to its argument when invoked with any number of parameters. </p>
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- <h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2>
- <div xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv"><pre class="synopsis"><span class="comment">// In header: <<a class="link" href="header/boost/vmd/identity_hpp.html" title="Header <boost/vmd/identity.hpp>">boost/vmd/identity.hpp</a>>
- </span>BOOST_VMD_IDENTITY(item)</pre></div>
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- <a name="idm45529680829952"></a><h2>Description</h2>
- <p>item = any single argument</p>
- <p>When BOOST_VMD_IDENTITY(item) is subsequently invoked with any number of parameters it expands to 'item'. Subsequently invoking the macro is done as 'BOOST_VMD_IDENTITY(item)(zero_or_more_arguments)'.</p>
- <p>The macro is equivalent to the Boost PP macro BOOST_PP_IDENTITY(item) with the difference being that BOOST_PP_IDENTITY(item) is always invoked with no arguments, as in 'BOOST_VMD_IDENTITY(item)()' whereas BOOST_VMD_IDENTITY can be invoked with any number of arguments.</p>
- <p>The macro is meant to be used in BOOST_PP_IF and BOOST_PP_IIF statements when only one of the clauses needs to be invoked with calling another macro and the other is meant to return an 'item'.</p>
- <p>returns = the macro as 'BOOST_VMD_IDENTITY(item)', when invoked with any number of parameters as in '(zero_or_more_arguments)', returns 'item'. The macro itself returns 'item BOOST_VMD_EMPTY'. </p>
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