projects / ceph.git / blame
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|---|---|---|
| 7c673cae FG |
1 | <html> |
| 2 | <head> | |
| 3 | <title>BOOST_PP_DEDUCE_D</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_DEDUCE_D</b> macro manually deduces the state of the <b>BOOST_PP_WHILE</b> construct. | |
| 9 | </div> | |
| 10 | <h4>Usage</h4> | |
| 11 | <div class="code"> | |
| 12 | <b>BOOST_PP_DEDUCE_D</b>() | |
| 13 | </div> | |
| 14 | <h4>Remarks</h4> | |
| 15 | <div> | |
| 16 | This macro is intended to avoid the use of <i>automatic-recursion</i> at deep expansion depths. | |
| 17 | <i>Automatic-recursion</i> at such depths can be inefficient on some preprocessors. | |
| 18 | It is not intended to be used directly with the invocation of macros with a <b>_D</b> suffix such as: | |
| 19 | <div> | |
| 20 | <b>BOOST_PP_ADD_D</b>(<b>BOOST_PP_DEDUCE_D</b>(), <i>x</i>, <i>y</i>) | |
| 21 | </div> | |
| 22 | If it is used in this context, the <b>_D</b> macro will fail. | |
| 23 | The <b>_D</b> macros directly concatenate to the <i>d</i> parameter that is passed to them, | |
| 24 | which would prevent <b>BOOST_PP_DEDUCE_D</b>() from expanding. | |
| 25 | Furthermore, it is pointless to use this macro in a situation such as this | |
| 26 | because it would already be too late to gain any efficiency. | |
| 27 | </div> | |
| 28 | <h4>See Also</h4> | |
| 29 | <ul> | |
| 30 | <li><a href="while.html">BOOST_PP_WHILE</a></li> | |
| 31 | </ul> | |
| 32 | <h4>Requirements</h4> | |
| 33 | <div> | |
| 34 | <b>Header:</b> <a href="../headers/control/deduce_d.html"><boost/preprocessor/control/deduce_d.hpp></a> | |
| 35 | </div> | |
| 36 | <h4>Sample Code</h4> | |
| 37 | <div><pre> | |
| 38 | #include <<a href="../headers/arithmetic/add.html">boost/preprocessor/arithmetic/add.hpp</a>> | |
| 39 | #include <<a href="../headers/arithmetic/inc.html">boost/preprocessor/arithmetic/inc.hpp</a>> | |
| 40 | #include <<a href="../headers/arithmetic/sub.html">boost/preprocessor/arithmetic/sub.hpp</a>> | |
| 41 | #include <<a href="../headers/control/deduce_d.html">boost/preprocessor/control/deduce_d.hpp</a>> | |
| 42 | #include <<a href="../headers/punctuation/comma_if.html">boost/preprocessor/punctuation/comma_if.hpp</a>> | |
| 43 | #include <<a href="../headers/repetition/repeat.html">boost/preprocessor/repetition/repeat.hpp</a>> | |
| 44 | #include <<a href="../headers/tuple/elem.html">boost/preprocessor/tuple/elem.hpp</a>> | |
| 45 | ||
| 46 | #define RANGE(first, last) \ | |
| 47 | <a href="repeat.html">BOOST_PP_REPEAT</a>( \ | |
| 48 | <a href="inc.html">BOOST_PP_INC</a>( \ | |
| 49 | <a href="sub.html">BOOST_PP_SUB</a>(last, first) \ | |
| 50 | ), \ | |
| 51 | RANGE_M, \ | |
| 52 | (first, <a href="deduce_d.html">BOOST_PP_DEDUCE_D</a>()) \ | |
| 53 | ) \ | |
| 54 | /**/ | |
| 55 | ||
| 56 | #define RANGE_M(z, n, data) \ | |
| 57 | RANGE_M_2( \ | |
| 58 | n, \ | |
| 59 | <a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(2, 0, data), \ | |
| 60 | <a href="tuple_elem.html">BOOST_PP_TUPLE_ELEM</a>(2, 1, data) \ | |
| 61 | ) \ | |
| 62 | /**/ | |
| 63 | ||
| 64 | #define RANGE_M_2(n, first, d) \ | |
| 65 | <a href="comma_if.html">BOOST_PP_COMMA_IF</a>(n) <a href="add_d.html">BOOST_PP_ADD_D</a>(d, n, first) \ | |
| 66 | /**/ | |
| 67 | ||
| 68 | RANGE(5, 10) // expands to 5, 6, 7, 8, 9, 10 | |
| 69 | </pre></div> | |
| 70 | <hr size="1"> | |
| 71 | <div style="margin-left: 0px;"> | |
| 72 |