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<html>
<head>
<title>BOOST_PP_FOR</title>
<link rel="stylesheet" type="text/css" href="../styles.css">
<script language="javascript" type="text/javascript" src="../scripts.js"></script>
</head>
<body onload="init('sample');">
<div style="margin-left: 0px;">
The <b>BOOST_PP_FOR</b> macro represents a generalized horizontal repetition construct.
</div>
<h4>Usage</h4>
<div class="code">
<b>BOOST_PP_FOR</b>(<i>state</i>, <i>pred</i>, <i>op</i>, <i>macro</i>)
</div>
<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>).&nbsp;
This macro must expand to an integer in the range of <i>0</i> to <b>BOOST_PP_LIMIT_MAG</b>.&nbsp;
<b>BOOST_PP_FOR</b> repeatedly expands <i>macro</i> while this predicate returns non-zero.&nbsp;
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>).&nbsp;
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;
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>).&nbsp;
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;
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>
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;
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;
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>
<div>
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>.&nbsp;
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> &nbsp;<a href="../headers/repetition/for.hpp.html">&lt;boost/preprocessor/repetition/for.hpp&gt;</a>
</div>
<h4><a class="local" onclick="toggle('sample');" onmouseover="change(this);" onmouseout="revert(this);">Sample Code</a></h4>
<div id="sample"><pre>
#include &lt;boost/preprocessor/arithmetic/inc.hpp&gt;
#include &lt;boost/preprocessor/comparison/not_equal.hpp&gt;
#include &lt;boost/preprocessor/repetition/for.hpp&gt;
#include &lt;boost/preprocessor/tuple/elem.hpp&gt;
#define PRED(r, state) /* ....................... */ \
BOOST_PP_NOT_EQUAL( \
BOOST_PP_TUPLE_ELEM(2, 0, state), \
BOOST_PP_INC(BOOST_PP_TUPLE_ELEM(2, 1, state)) \
) \
/**/
#define OP(r, state) /* .......................... */ \
( \
BOOST_PP_INC(BOOST_PP_TUPLE_ELEM(2, 0, state)), \
BOOST_PP_TUPLE_ELEM(2, 1, state) \
) \
/**/
#define MACRO(r, state) BOOST_PP_TUPLE_ELEM(2, 0, state)
BOOST_PP_FOR((5, 10), PRED, OP, MACRO) // expands to 5 6 7 8 9 10
<pre></div>
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