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| <head> |
| <title>BOOST_PP_FOR_r</title> |
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| </head> |
| <body> |
| <div style="margin-left: 0px;"> |
| The <b>BOOST_PP_FOR_<i>r</i></b> macro represents a reentry into the <b>BOOST_PP_FOR</b> repetition construct. |
| </div> |
| <h4>Usage</h4> |
| <div class="code"> |
| <b>BOOST_PP_FOR_</b> ## <i>r</i>(<i>state</i>, <i>pred</i>, <i>op</i>, <i>macro</i>) |
| </div> |
| <h4>Arguments</h4> |
| <dl> |
| <dt>r</dt> |
| <dd> |
| The next available <b>BOOST_PP_FOR</b> repetition. |
| </dd> |
| <dt>state</dt> |
| <dd> |
| The initial state. |
| </dd> |
| <dt>pred</dt> |
| <dd> |
| A binary predicate of the form <i>pred</i>(<i>r</i>, <i>state</i>). |
| This macro must expand to an integer in the range of <i>0</i> to <b>BOOST_PP_LIMIT_MAG</b>. |
| <b>BOOST_PP_FOR</b> repeatedly expands <i>macro</i> while this predicate returns non-zero. |
| This macro is called with the next available <b>BOOST_PP_FOR</b> repetition and the current <i>state</i>. |
| </dd> |
| <dt>op</dt> |
| <dd> |
| A binary operation of the form <i>op</i>(<i>r</i>, <i>state</i>). |
| 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>. |
| 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>. |
| </dd> |
| <dt>macro</dt> |
| <dd> |
| A binary macro of the form <i>macro</i>(<i>r</i>, <i>state</i>). |
| 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>. |
| This macro is is repeated by <b>BOOST_PP_FOR</b> until <i>pred</i> returns <i>0</i>. |
| </dd> |
| </dl> |
| <h4>Remarks</h4> |
| <div> |
| This macro expands to the sequence: |
| <div> |
| <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>) ... )) |
| </div> |
| </div> |
| <div> |
| At certain times, it may be necessary to perform the concatenation with <b>BOOST_PP_CAT</b> rather than the preprocessor token-pasting operator. |
| This happens when the <i>r</i> value is a macro invocation itself. |
| It needs a delay to allow it to expand. |
| The syntax in such a scenario becomes: |
| <div> |
| <b>BOOST_PP_CAT</b>(<b>BOOST_PP_FOR_</b>, <i>r</i>)(<i>state</i>, <i>pred</i>, <i>op</i>, <i>macro</i>) |
| </div> |
| </div> |
| <h4>See Also</h4> |
| <ul> |
| <li><a href="cat.html">BOOST_PP_CAT</a></li> |
| <li><a href="for.html">BOOST_PP_FOR</a></li> |
| <li><a href="limit_mag.html">BOOST_PP_LIMIT_MAG</a></li> |
| </ul> |
| <h4>Requirements</h4> |
| <div> |
| <b>Header:</b> <a href="../headers/repetition/for.html"><boost/preprocessor/repetition/for.hpp></a> |
| </div> |
| <h4>Sample Code</h4> |
| <div><pre> |
| #include <<a href="../headers/arithmetic/dec.html">boost/preprocessor/arithmetic/dec.hpp</a>> |
| #include <<a href="../headers/arithmetic/inc.html">boost/preprocessor/arithmetic/inc.hpp</a>> |
| #include <<a href="../headers/comparison/not_equal.html">boost/preprocessor/comparison/not_equal.hpp</a>> |
| #include <<a href="../headers/punctuation/comma_if.html">boost/preprocessor/punctuation/comma_if.hpp</a>> |
| #include <<a href="../headers/repetition/for.html">boost/preprocessor/repetition/for.hpp</a>> |
| #include <<a href="../headers/tuple/elem.html">boost/preprocessor/tuple/elem.hpp</a>> |
| |
| #define PRED(r, state) \ |
| <a href="not_equal.html">BOOST_PP_NOT_EQUAL</a>( \ |
| <a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(4, 0, state), \ |
| <a href="inc.html">BOOST_PP_INC</a>( \ |
| <a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(4, 1, state) \ |
| ) \ |
| ) \ |
| /**/ |
| |
| #define OP(r, state) \ |
| ( \ |
| <a href="inc.html">BOOST_PP_INC</a>( \ |
| <a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(4, 0, state) \ |
| ), \ |
| <a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(4, 1, state), \ |
| <a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(4, 2, state), \ |
| <a href="inc.html">BOOST_PP_INC</a>( \ |
| <a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(4, 3, state) \ |
| ) \ |
| ) \ |
| /**/ |
| |
| #define MACRO(r, state) \ |
| <a href="comma_if.html">BOOST_PP_COMMA_IF</a>( \ |
| <a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(4, 3, state) \ |
| ) template< \ |
| <a href="for_r.html">BOOST_PP_FOR_</a> ## r( \ |
| (0, <a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(4, 0, state), _, 0), \ |
| PRED_2, OP, MACRO_2 \ |
| ) \ |
| > class <a href="cat.html">BOOST_PP_CAT</a>( \ |
| <a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(4, 2, state), \ |
| <a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(4, 0, state) \ |
| ) \ |
| /**/ |
| |
| #define PRED_2(r, state) \ |
| <a href="not_equal.html">BOOST_PP_NOT_EQUAL</a>( \ |
| <a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(4, 0, state), \ |
| <a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(4, 1, state) \ |
| ) \ |
| /**/ |
| |
| #define MACRO_2(r, state) \ |
| <a href="comma_if.html">BOOST_PP_COMMA_IF</a>( \ |
| <a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(4, 0, state) \ |
| ) class \ |
| /**/ |
| |
| #define TEMPLATE_TEMPLATE(low, high, name) \ |
| <a href="for.html">BOOST_PP_FOR</a>( \ |
| (low, high, name, 0), \ |
| PRED, OP, MACRO \ |
| ) \ |
| /**/ |
| |
| TEMPLATE_TEMPLATE(2, 4, T) |
| /* |
| expands to... |
| template<class, class> class T2, |
| template<class, class, class> class T3, |
| template<class, class, class, class> class T4 |
| */ |
| </pre></div> |
| <hr size="1"> |
| <div style="margin-left: 0px;"> |
| <i>© Copyright <a href="http://www.housemarque.com" target="_top">Housemarque Oy</a> 2002</i> |
| </br><i>© Copyright Paul Mensonides 2002</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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