projects / ceph.git / blame
| Commit | Line | Data |
|---|---|---|
| 7c673cae FG |
1 | <html> |
| 2 | <head> | |
| 3 | <title>BOOST_PP_LIST_AT</title> | |
| 4 | <link rel="stylesheet" type="text/css" href="../styles.css"> | |
| 5 | </head> | |
| 6 | <body> | |
| 7 | <div style="margin-left: 0px;"> | |
| 8 | The <b>BOOST_PP_LIST_AT</b> macro extracts an element in a <i>list</i>. | |
| 9 | </div> | |
| 10 | <h4>Usage</h4> | |
| 11 | <div class="code"> | |
| 12 | <b>BOOST_PP_LIST_AT</b>(<i>list</i>, <i>index</i>) | |
| 13 | </div> | |
| 14 | <h4>Arguments</h4> | |
| 15 | <dl> | |
| 16 | <dt>list</dt> | |
| 17 | <dd> | |
| 18 | The <i>list</i> from which a element is to be extracted. | |
| 19 | This <i>list</i> must have at least <i>index</i> + <i>1</i> elements. | |
| 20 | </dd> | |
| 21 | <dt>index</dt> | |
| 22 | <dd> | |
| 23 | The zero-based position in the <i>list</i> of the element to be extracted. | |
| 24 | </dd> | |
| 25 | </dl> | |
| 26 | <h4>Remarks</h4> | |
| 27 | <div> | |
| 28 | Previously, this macro could not be used inside <b>BOOST_PP_WHILE</b>. | |
| 29 | There is no longer any such restriction. | |
| 30 | It is more efficient, however, to use <b>BOOST_PP_LIST_AT_D</b> in such a situation. | |
| 31 | </div> | |
| 32 | <h4>See Also</h4> | |
| 33 | <ul> | |
| 34 | <li><a href="list_at_d.html">BOOST_PP_LIST_AT_D</a></li> | |
| 35 | </ul> | |
| 36 | <h4>Requirements</h4> | |
| 37 | <div> | |
| 38 | <b>Header:</b> <a href="../headers/list/at.html"><boost/preprocessor/list/at.hpp></a> | |
| 39 | </div> | |
| 40 | <h4>Sample Code</h4> | |
| 41 | <div><pre> | |
| 42 | #include <<a href="../headers/list/at.html">boost/preprocessor/list/at.hpp</a>> | |
| 43 | ||
| 44 | #define LIST (a, (b, (c, <a href="nil.html">BOOST_PP_NIL</a>))) | |
| 45 | ||
| 46 | <a href="list_at.html">BOOST_PP_LIST_AT</a>(LIST, 0) // expands to a | |
| 47 | <a href="list_at.html">BOOST_PP_LIST_AT</a>(LIST, 2) // expands to c | |
| 48 | </pre></div> | |
| 49 | <hr size="1"> | |
| 50 | <div style="margin-left: 0px;"> | |
| 51 |