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<html>
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<head>
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<title>BOOST_PP_SEQ_FOLD_LEFT</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_SEQ_FOLD_LEFT</b> macro folds (or accumulates) the elements of
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a <i>seq</i> left-to-right.
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</div>
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<h4>
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Usage
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</h4>
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<div class="code">
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<b>BOOST_PP_SEQ_FOLD_LEFT</b>(<i>op</i>, <i>state</i>, <i>seq</i>)
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</div>
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<h4>
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Arguments
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</h4>
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<dl>
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<dt>op</dt>
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<dd>
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A ternary operation of the form <i>op</i>(<i>s</i>, <i>state</i>, <i>elem</i>).
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This macro is called for each element in <i>seq</i>--each time returning a new <i>state</i>.
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This operation is expanded by <b>BOOST_PP_SEQ_FOLD_LEFT</b> with the next
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available fold step, the current <i>state</i>, and the current element.
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</dd>
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<dt>state</dt>
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<dd>
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The initial state of the fold.
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</dd>
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<dt>seq</dt>
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<dd>
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The <i>seq</i> to be folded.
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</dd>
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</dl>
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<h4>
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Remarks
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</h4>
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<div>
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For the <i>seq</i>, (<i>0</i>)(<i>1</i>)(<i>2</i>), this macro expands to:
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<div>
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<i>op</i>(<i>s</i>, <i>op</i>(<i>s</i>, <i>op</i>(<i>s</i>, <i>state</i>, <i>0</i>),
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<i>1</i>), <i>2</i>)
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</div>
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</div>
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<div>
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For maximum efficiency, <b>BOOST_PP_SEQ_FOLD_LEFT</b> can be reentered with <b>BOOST_PP_SEQ_FOLD_LEFT_<i>s</i></b>.
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</div>
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<h4>
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See Also
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</h4>
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<ul>
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<li>
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<a href="seq_fold_left_s.html">BOOST_PP_SEQ_FOLD_LEFT_<i>s</i></a></li>
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</ul>
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<h4>
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Requirements
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</h4>
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<div>
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<b>Header:</b> <a href="../headers/seq/fold_left.hpp.html"><boost/preprocessor/seq/fold_left.hpp></a>
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</div>
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<h4>
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Sample Code
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</h4>
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<div>
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<pre>
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#include <<a href="../headers/cat.hpp.html">boost/preprocessor/cat.hpp</a>>
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#include <<a href="../headers/seq/fold_left.hpp.html">boost/preprocessor/seq/fold_left.hpp</a>>
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#define SEQ (b)(o)(o)(s)(t)
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#define OP(s, state, x) <a href="cat.html">BOOST_PP_CAT</a>(state, x)
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<a href="seq_fold_left.html">BOOST_PP_SEQ_FOLD_LEFT</a>(OP, <a href="seq_head.html">BOOST_PP_SEQ_HEAD</a>(SEQ), <a href="seq_tail.html">BOOST_PP_SEQ_TAIL</a>(SEQ)) // expands to boost
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</pre>
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</div>
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</body>
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2002-10-13 05:47:23 +00:00
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</html>
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