1<html> 2<head> 3 <title>BOOST_PP_LPAREN_IF</title> 4 <link rel="stylesheet" type="text/css" href="../styles.css"> 5</head> 6<body> 7 <div style="margin-left: 0px;"> 8 The <b>BOOST_PP_LPAREN_IF</b> macro conditionally expands to a left parenthesis. 9 </div> 10 <h4>Usage</h4> 11 <div class="code"> 12 <b>BOOST_PP_LPAREN_IF</b>(<i>cond</i>) 13 </div> 14 <h4>Arguments</h4> 15 <dl> 16 <dt>cond</dt> 17 <dd> 18 The condition that determines if a the macro expands to a left parenthesis or nothing. 19 Valid values range from <i>0</i> to <b>BOOST_PP_LIMIT_MAG</b>. 20 </dd> 21 </dl> 22 <h4>Remarks</h4> 23 <div> 24 If <i>cond</i> expands to <i>0</i>, this macro expands to nothing. 25 Otherwise, it expands to a left parenthesis. 26 </div> 27 <div> 28 The preprocessor interprets parentheses as delimiters in macro invocations. 29 Because of this, parentheses require special handling. 30 </div> 31 <h4>See Also</h4> 32 <ul> 33 <li><a href="limit_mag.html">BOOST_PP_LIMIT_MAG</a></li> 34 <li><a href="rparen_if.html">BOOST_PP_RPAREN_IF</a></li> 35 </ul> 36 <h4>Requirements</h4> 37 <div> 38 <b>Header:</b> <a href="../headers/punctuation/paren_if.html"><boost/preprocessor/punctuation/paren_if.hpp></a> 39 </div> 40 <h4>Sample Code</h4> 41<div><pre> 42#include <<a href="../headers/punctuation/paren_if.html">boost/preprocessor/punctuation/paren_if.hpp</a>> 43 44#define MACRO(c, x) <a href="lparen_if.html">BOOST_PP_LPAREN_IF</a>(c) x <a href="rparen_if.html">BOOST_PP_RPAREN_IF</a>(c) 45 46MACRO(0, text) // expands to text 47MACRO(1, text) // expands to (text) 48</pre></div> 49 <hr size="1"> 50 <div style="margin-left: 0px;"> 51 <i>� Copyright <a href="http://www.housemarque.com" target="_top">Housemarque Oy</a> 2002</i> 52 </br><i>� Copyright Paul Mensonides 2002</i> 53 </div> 54 <div style="margin-left: 0px;"> 55 <p><small>Distributed under the Boost Software License, Version 1.0. (See 56 accompanying file <a href="../../../../LICENSE_1_0.txt">LICENSE_1_0.txt</a> or 57 copy at <a href= 58 "http://www.boost.org/LICENSE_1_0.txt">www.boost.org/LICENSE_1_0.txt</a>)</small></p> 59 </div> 60</body> 61</html> 62