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| <title>BOOST_PP_FOR</title> |
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| The <b>BOOST_PP_FOR</b> macro represents a generalized horizontal repetition construct. |
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| <h4>Usage</h4> |
| <div class="code"> |
| <b>BOOST_PP_FOR</b>(<i>state</i>, <i>pred</i>, <i>op</i>, <i>macro</i>) |
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| <h4>Arguments</h4> |
| <dl> |
| <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: |
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| <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> |
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| 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. |
| 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>. |
| 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. |
| </div> |
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| 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>. |
| </div> |
| <div> |
| Previously, this macro could not be used recursively inside <b>BOOST_PP_FOR</b>. |
| This limitation no longer exists, as the library can automatically detect the next available <b>BOOST_PP_FOR</b> repetition. |
| </div> |
| <h4>See Also</h4> |
| <ul> |
| <li><a href="for_r.html">BOOST_PP_FOR_<i>r</i></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/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/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>(2, 0, state), \ |
| <a href="inc.html">BOOST_PP_INC</a>(<a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(2, 1, state)) \ |
| ) \ |
| /**/ |
| |
| #define OP(r, state) \ |
| ( \ |
| <a href="inc.html">BOOST_PP_INC</a>(<a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(2, 0, state)), \ |
| <a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(2, 1, state) \ |
| ) \ |
| /**/ |
| |
| #define MACRO(r, state) <a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(2, 0, state) |
| |
| <a href="for.html">BOOST_PP_FOR</a>((5, 10), PRED, OP, MACRO) // expands to 5 6 7 8 9 10 |
| </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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