ceph/src/boost/libs/preprocessor/doc/ref/for.html

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   3         <title>BOOST_PP_FOR</title>
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   8                 The <b>BOOST_PP_FOR</b> macro represents a generalized horizontal repetition construct.
   9         </div>
  10         <h4>Usage</h4>
  11                 <div class="code">
  12                         <b>BOOST_PP_FOR</b>(<i>state</i>, <i>pred</i>, <i>op</i>, <i>macro</i>)
  13                 </div>
  14         <h4>Arguments</h4>
  15                 <dl>
  16                         <dt>state</dt>
  17                         <dd>
  18                                 The initial state.
  19                         </dd>
  20                         <dt>pred</dt>
  21                         <dd>
  22                                 A binary predicate of the form <i>pred</i>(<i>r</i>, <i>state</i>).&nbsp;
  23                                 This macro must expand to an integer in the range of <i>0</i> to <b>BOOST_PP_LIMIT_MAG</b>.&nbsp;
  24                                 <b>BOOST_PP_FOR</b> repeatedly expands <i>macro</i> while this predicate returns non-zero.&nbsp;
  25                                 This macro is called with the next available <b>BOOST_PP_FOR</b> repetition and the current <i>state</i>.
  26                         </dd>
  27                         <dt>op</dt>
  28                         <dd>
  29                                 A binary operation of the form <i>op</i>(<i>r</i>, <i>state</i>).&nbsp;
  30                                 This operation is expanded by <b>BOOST_PP_FOR</b> with the next available <b>BOOST_PP_FOR</b> repetition and the current <i>state</i>.&nbsp;
  31                                 This macro is repeatedly applied to the <i>state</i>, each time producing a new <i>state</i>, until <i>pred</i> returns <i>0</i>.
  32                         </dd>
  33                         <dt>macro</dt>
  34                         <dd>
  35                                 A binary macro of the form <i>macro</i>(<i>r</i>, <i>state</i>).&nbsp;
  36                                 This macro is expanded by <b>BOOST_PP_FOR</b> with the next available <b>BOOST_PP_FOR</b> repetition and the current <i>state</i>.&nbsp;
  37                                 This macro is is repeated by <b>BOOST_PP_FOR</b> until <i>pred</i> returns <i>0</i>.
  38                         </dd>
  39                 </dl>
  40         <h4>Remarks</h4>
  41                 <div>
  42                         This macro expands to the sequence:
  43                         <div>
  44                                 <i>macro</i>(<i>r</i>, <i>state</i>) <i>macro</i>(<i>r</i>, <i>op</i>(<i>r</i>, <i>state</i>)) ... <i>macro</i>(<i>r</i>, <i>op</i>(<i>r</i>, ... <i>op</i>(<i>r</i>, <i>state</i>) ... ))
  45                         </div>
  46                 </div>
  47                 <div>
  48                         The <i>r</i> value that is passed to <i>pred</i>, <i>op</i>, and <i>macro</i> represents the next available <b>BOOST_PP_FOR</b> repetition.&nbsp;
  49                         Other macros that have <b>_R</b> suffix variants internally use <b>BOOST_PP_FOR</b>--for example, <b>BOOST_PP_LIST_FOR_EACH</b> and <b>BOOST_PP_LIST_FOR_EACH_R</b>.&nbsp;
  50                         Using these <b>_R</b> versions is not strictly necessary, but passing the <i>r</i> value (that is passed to <i>pred</i>, <i>op</i>, and <i>macro</i>) to these macros allows them to reenter <b>BOOST_PP_FOR</b> with maximum efficiency.
  51                 </div>
  52                 <div>
  53                         To directly use this <i>r</i> value, rather than simply passing it to another macro, see <b>BOOST_PP_FOR_<i>r</i></b>.
  54                 </div>
  55                 <div>
  56                         Previously, this macro could not be used recursively inside <b>BOOST_PP_FOR</b>.&nbsp;
  57                         This limitation no longer exists, as the library can automatically detect the next available <b>BOOST_PP_FOR</b> repetition.
  58                 </div>
  59         <h4>See Also</h4>
  60                 <ul>
  61                         <li><a href="for_r.html">BOOST_PP_FOR_<i>r</i></a></li>
  62                         <li><a href="limit_mag.html">BOOST_PP_LIMIT_MAG</a></li>
  63                 </ul>
  64         <h4>Requirements</h4>
  65                 <div>
  66                         <b>Header:</b> &nbsp;<a href="../headers/repetition/for.html">&lt;boost/preprocessor/repetition/for.hpp&gt;</a>
  67                 </div>
  68         <h4>Sample Code</h4>
  69 <div><pre>
  70 #include &lt;<a href="../headers/arithmetic/inc.html">boost/preprocessor/arithmetic/inc.hpp</a>&gt;
  71 #include &lt;<a href="../headers/comparison/not_equal.html">boost/preprocessor/comparison/not_equal.hpp</a>&gt;
  72 #include &lt;<a href="../headers/repetition/for.html">boost/preprocessor/repetition/for.hpp</a>&gt;
  73 #include &lt;<a href="../headers/tuple/elem.html">boost/preprocessor/tuple/elem.hpp</a>&gt;
  74
  75 #define PRED(r, state) \
  76    <a href="not_equal.html">BOOST_PP_NOT_EQUAL</a>( \
  77       <a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(2, 0, state), \
  78       <a href="inc.html">BOOST_PP_INC</a>(<a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(2, 1, state)) \
  79    ) \
  80    /**/
  81
  82 #define OP(r, state) \
  83    ( \
  84       <a href="inc.html">BOOST_PP_INC</a>(<a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(2, 0, state)), \
  85       <a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(2, 1, state) \
  86    ) \
  87    /**/
  88
  89 #define MACRO(r, state) <a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(2, 0, state)
  90
  91 <a href="for.html">BOOST_PP_FOR</a>((5, 10), PRED, OP, MACRO) // expands to 5 6 7 8 9 10
  92 </pre></div>
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  95                 <i>© Copyright <a href="http://www.housemarque.com" target="_top">Housemarque Oy</a> 2002</i>
  96                 </br><i>© Copyright Paul Mensonides 2002</i>
  97         </div>
  98         <div style="margin-left: 0px;">
  99                 <p><small>Distributed under the Boost Software License, Version 1.0. (See
 100                 accompanying file <a href="../../../../LICENSE_1_0.txt">LICENSE_1_0.txt</a> or
 101                 copy at <a href=
 102                 "http://www.boost.org/LICENSE_1_0.txt">www.boost.org/LICENSE_1_0.txt</a>)</small></p>
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