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- <title>BOOST_PP_FOR_r</title>
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- <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>
- <li><a href="for_r_macros.html"><span style="color: gray;">Macros with R
- re-entrancy forms</span></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<br>
- </i><i>© Copyright Edward Diener 2014</i><br>
- </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>
- </div>
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- </html>
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