preprocessor/doc/ref/is_begin_parens.html

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<title>BOOST_PP_IS_BEGIN_PARENS</title>
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<div style="margin-left: 0px;"> The <b>BOOST_PP_IS_BEGIN_PAREN</b>S
determines whether the input starts with a set of parenthesis.</div>
<h4>Usage</h4>
<div class="code"> <b>BOOST_PP_IS_BEGIN_PARENS</b>(...) <a href="../topics/variadic_macros.html#VNotation"
target="_self"><sup>(v)</sup></a></div>
<h4>Arguments</h4>
<h4>&nbsp;&nbsp;&nbsp; ...&nbsp;&nbsp;&nbsp; <span style="font-weight: normal;">&nbsp;&nbsp;&nbsp;
&nbsp;&nbsp;&nbsp; The input as variadic data.</span></h4>
<h4>Remarks</h4>
<div> If the input input begins with a parenthesis, with any data within
that parenthesis, the macro returns 1, otherwise it returns 0. Data may
follow the beginning parenthesis and the macro still will return 1.<br>
<br>
For Visual Studio 2005 ( VC8 ) the input data must be a single parameter
else a compilation error will occur.</div>
<h4>See Also</h4>
<ul>
<li><a href="remove_parens.html">BOOST_PP_REMOVE_PARENS</a></li>
</ul>
<h4>Requirements</h4>
<div> <b>Header:</b> &nbsp;<a href="../headers/punctuation/is_begin_parens.html">&lt;boost/preprocessor/punctuation/is_begin_parens.hpp&gt;</a>
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<h4>Sample Code</h4>
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<pre>#include &lt;<a href="../headers/punctuation/is_begin_parens.html">boost/preprocessor/punctuation/is_begin_parens.hpp</a>&gt;
#define VARDATA more_data , more_params<br>#define VARDATAP ( data ) more_data , more_params<br>#define DATA data<br>#define DATAP ( data ) more_data<br>
BOOST_PP_IS_BEGIN_PARENS(VARDATA) // expands to 0, compiler error with VC8
BOOST_PP_IS_BEGIN_PARENS(VARDATAP) // expands to 1, compiler error with VC8<br><br>BOOST_PP_IS_BEGIN_PARENS(DATA) // expands to 0
BOOST_PP_IS_BEGIN_PARENS(DATAP) // expands to 1<br><br>BOOST_PP_IS_BEGIN_PARENS() // expands to 0<br>
</pre></div>
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<div style="margin-left: 0px;"> <i><EFBFBD> Copyright Edward Diener 2014</i> </div>
<div style="margin-left: 0px;">
<p><small>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">www.boost.org/LICENSE_1_0.txt</a>)</small></p>
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