projects / ceph.git / blame
| Commit | Line | Data |
|---|---|---|
| 7c673cae FG |
1 | .. Metafunctions/Bitwise Operations//shift_left |
| 2 | ||
| 3 | shift_left | |
| 4 | ========== | |
| 5 | ||
| 6 | Synopsis | |
| 7 | -------- | |
| 8 | ||
| 9 | .. parsed-literal:: | |
| 10 | ||
| 11 | template< | |
| 12 | typename T | |
| 13 | , typename Shift | |
| 14 | > | |
| 15 | struct shift_left | |
| 16 | { | |
| 17 | typedef |unspecified| type; | |
| 18 | }; | |
| 19 | ||
| 20 | ||
| 21 | ||
| 22 | Description | |
| 23 | ----------- | |
| 24 | ||
| 25 | Returns the result of bitwise *shift left* (``<<``) operation on ``T``. | |
| 26 | ||
| 27 | ||
| 28 | Header | |
| 29 | ------ | |
| 30 | ||
| 31 | .. parsed-literal:: | |
| 32 | ||
| 33 | #include <boost/mpl/shift_left.hpp> | |
| 34 | #include <boost/mpl/bitwise.hpp> | |
| 35 | ||
| 36 | ||
| 37 | Model of | |
| 38 | -------- | |
| 39 | ||
| 40 | |Numeric Metafunction| | |
| 41 | ||
| 42 | ||
| 43 | Parameters | |
| 44 | ---------- | |
| 45 | ||
| 46 | +---------------+-------------------------------+---------------------------+ | |
| 47 | | Parameter | Requirement | Description | | |
| 48 | +===============+===============================+===========================+ | |
| 49 | | ``T`` | |Integral Constant| | A value to shift. | | |
| 50 | +---------------+-------------------------------+---------------------------+ | |
| 51 | | ``Shift`` | Unsigned |Integral Constant| | A shift distance. | | |
| 52 | +---------------+-------------------------------+---------------------------+ | |
| 53 | ||
| 54 | |Note:| |numeric metafunction note| |-- end note| | |
| 55 | ||
| 56 | ||
| 57 | Expression semantics | |
| 58 | -------------------- | |
| 59 | ||
| 60 | For arbitrary |Integral Constant| ``c`` and unsigned |Integral Constant| ``shift``: | |
| 61 | ||
| 62 | ||
| 63 | .. parsed-literal:: | |
| 64 | ||
| 65 | typedef shift_left<c,shift>::type r; | |
| 66 | ||
| 67 | :Return type: | |
| 68 | |Integral Constant|. | |
| 69 | ||
| 70 | :Semantics: | |
| 71 | Equivalent to | |
| 72 | ||
| 73 | .. parsed-literal:: | |
| 74 | ||
| 75 | typedef integral_c< | |
| 76 | c::value_type | |
| 77 | , ( c::value << shift::value ) | |
| 78 | > r; | |
| 79 | ||
| 80 | .. .......................................................................... | |
| 81 | ||
| 82 | .. parsed-literal:: | |
| 83 | ||
| 84 | typedef shift_left<c,shift> r; | |
| 85 | ||
| 86 | :Return type: | |
| 87 | |Integral Constant|. | |
| 88 | ||
| 89 | :Semantics: | |
| 90 | Equivalent to | |
| 91 | ||
| 92 | .. parsed-literal:: | |
| 93 | ||
| 94 | struct r : shift_left<c,shift>::type {}; | |
| 95 | ||
| 96 | ||
| 97 | Complexity | |
| 98 | ---------- | |
| 99 | ||
| 100 | Amortized constant time. | |
| 101 | ||
| 102 | ||
| 103 | Example | |
| 104 | ------- | |
| 105 | ||
| 106 | .. parsed-literal:: | |
| 107 | ||
| 108 | typedef integral_c<unsigned,0> u0; | |
| 109 | typedef integral_c<unsigned,1> u1; | |
| 110 | typedef integral_c<unsigned,2> u2; | |
| 111 | typedef integral_c<unsigned,8> u8; | |
| 112 | ||
| 113 | BOOST_MPL_ASSERT_RELATION( (shift_left<u0,u0>::value), ==, 0 ); | |
| 114 | BOOST_MPL_ASSERT_RELATION( (shift_left<u1,u0>::value), ==, 1 ); | |
| 115 | BOOST_MPL_ASSERT_RELATION( (shift_left<u1,u1>::value), ==, 2 ); | |
| 116 | BOOST_MPL_ASSERT_RELATION( (shift_left<u2,u1>::value), ==, 4 ); | |
| 117 | BOOST_MPL_ASSERT_RELATION( (shift_left<u8,u1>::value), ==, 16 ); | |
| 118 | ||
| 119 | ||
| 120 | See also | |
| 121 | -------- | |
| 122 | ||
| 123 | |Bitwise Operations|, |Numeric Metafunction|, |numeric_cast|, |shift_right|, |bitand_| | |
| 124 | ||
| 125 | ||
| 126 |