forked from boostorg/preprocessor
72 lines
2.8 KiB
HTML
72 lines
2.8 KiB
HTML
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<html>
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<head>
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<title>BOOST_PP_DEDUCE_D</title>
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<link rel="stylesheet" type="text/css" href="../styles.css">
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</head>
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<body>
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<div style="margin-left: 0px;">
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The <b>BOOST_PP_DEDUCE_D</b> macro manually deduces the state of the <b>BOOST_PP_WHILE</b> construct.
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</div>
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<h4>Usage</h4>
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<div class="code">
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<b>BOOST_PP_DEDUCE_D</b>()
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</div>
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<h4>Remarks</h4>
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<div>
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This macro is intended to avoid the use of <i>automatic-recursion</i> at deep expansion depths.
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<i>Automatic-recursion</i> at such depths can be inefficient on some preprocessors.
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It is not intended to be used directly with the invocation of macros with a <b>_D</b> suffix such as:
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<div>
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<b>BOOST_PP_ADD_D</b>(<b>BOOST_PP_DEDUCE_D</b>(), <i>x</i>, <i>y</i>)
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</div>
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If it is used in this context, the <b>_D</b> macro will fail.
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The <b>_D</b> macros directly concatenate to the <i>d</i> parameter that is passed to them,
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which would prevent <b>BOOST_PP_DEDUCE_D</b>() from expanding.
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Furthermore, it is pointless to use this macro in a situation such as this
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because it would already be too late to gain any efficiency.
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</div>
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<h4>See Also</h4>
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<ul>
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<li><a href="while.html">BOOST_PP_WHILE</a></li>
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</ul>
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<h4>Requirements</h4>
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<div>
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<b>Header:</b> <a href="../headers/control/deduce_d.hpp.html"><boost/preprocessor/control/deduce_d.hpp></a>
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</div>
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<h4>Sample Code</h4>
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<div><pre>
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#include <<a href="../headers/arithmetic/add.hpp.html">boost/preprocessor/arithmetic/add.hpp</a>>
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#include <<a href="../headers/arithmetic/inc.hpp.html">boost/preprocessor/arithmetic/inc.hpp</a>>
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#include <<a href="../headers/arithmetic/sub.hpp.html">boost/preprocessor/arithmetic/sub.hpp</a>>
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#include <<a href="../headers/control/deduce_d.hpp.html">boost/preprocessor/control/deduce_d.hpp</a>>
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#include <<a href="../headers/punctuation/comma_if.hpp.html">boost/preprocessor/punctuation/comma_if.hpp</a>>
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#include <<a href="../headers/repetition/repeat.hpp.html">boost/preprocessor/repetition/repeat.hpp</a>>
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#include <<a href="../headers/tuple/elem.hpp.html">boost/preprocessor/tuple/elem.hpp</a>>
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#define RANGE(first, last) \
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<a href="repeat.html">BOOST_PP_REPEAT</a>( \
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<a href="inc.html">BOOST_PP_INC</a>( \
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<a href="sub.html">BOOST_PP_SUB</a>(last, first) \
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, \
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RANGE_M, \
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(first, <a href="deduce_d.html">BOOST_PP_DEDUCE_D</a>()) \
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) \
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/**/
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#define RANGE_M(z, n, data) \
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RANGE_M_2( \
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n, \
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<a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(2, 0, data), \
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<a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(2, 1, data) \
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) \
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/**/
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#define RANGE_M_2(n, first, d) \
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<a href="comma_if.html">BOOST_PP_COMMA_IF</a>(n) <a href="add_d.html">BOOST_PP_ADD_D</a>(d, n, first) \
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/**/
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RANGE(5, 10) // expands to 5, 6, 7, 8, 9, 10
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</pre></div>
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</body>
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</html>
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