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2002-09-08 09:40:56 +00:00
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<title>BOOST_PP_ADD_D</title>
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The <b>BOOST_PP_ADD_D</b> macro expands to the sum of its second and third arguments.&nbsp;
It reenters <b>BOOST_PP_WHILE</b> with maximum efficiency.
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<h4>Usage</h4>
<div class="code">
<b>BOOST_PP_ADD_D</b>(<i>d</i>, <i>x</i>, <i>y</i>)
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<h4>Arguments</h4>
<dl>
<dt>d</dt>
<dd>
The next available <b>BOOST_PP_WHILE</b> iteration.&nbsp;
</dd>
<dt>x</dt>
<dd>
The first addend of the operation.&nbsp;
Valid values range from <i>0</i> to <b>BOOST_PP_LIMIT_MAG</b>.
</dd>
<dt>y</dt>
<dd>
The second addend of the operation.&nbsp;
Valid values range from <i>0</i> to <b>BOOST_PP_LIMIT_MAG</b>.
</dd>
</dl>
<h4>Remarks</h4>
<div>
If the sum of <i>x</i> and <i>y</i> is greater than <b>BOOST_PP_LIMIT_MAG</b>, the result is saturated to <b>BOOST_PP_LIMIT_MAG</b>.
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<div>
This macro is the most efficient when <i>x</i> is less than or equal to <i>y</i>.&nbsp;
However, the efficiency gain is not worth actually comparing the two arguments prior to invocation.&nbsp;
In other words, <i>x</i> should be the addend that is <i>most likely</i> to be the largest of the two operands.
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<h4>See Also</h4>
<ul>
<li><a href="add.html">BOOST_PP_ADD</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/arithmetic/add.hpp.html">&lt;boost/preprocessor/arithmetic/add.hpp&gt;</a>
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<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/add.hpp&gt;
#include &lt;boost/preprocessor/arithmetic/dec.hpp&gt;
#include &lt;boost/preprocessor/control/while.hpp&gt;
#include &lt;boost/preprocessor/tuple/elem.hpp&gt;
#define PRED(d, data) BOOST_PP_TUPLE_ELEM(2, 0, data)
#define OP(d, data) /* ............... */ \
( \
BOOST_PP_DEC( \
BOOST_PP_TUPLE_ELEM(2, 0, data) \
), \
BOOST_PP_ADD_D( \
d, \
BOOST_PP_TUPLE_ELEM(2, 1, data), \
2 \
) \
) \
/**/
// increment 'x' by 2 'n' times
#define STRIDE(x, n) BOOST_PP_TUPLE_ELEM(2, 1, BOOST_PP_WHILE(PRED, OP, (n, x)))
STRIDE(10, 2) // expands to 14
STRIDE(51, 6) // expands to 63
<pre></div>
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