projects / ceph.git / blame
| Commit | Line | Data |
|---|---|---|
| 7c673cae FG |
1 | .. Iterators/Iterator Metafunctions//advance |10 |
| 2 | ||
| 3 | advance | |
| 4 | ======= | |
| 5 | ||
| 6 | Synopsis | |
| 7 | -------- | |
| 8 | ||
| 9 | .. parsed-literal:: | |
| 10 | ||
| 11 | template< | |
| 12 | typename Iterator | |
| 13 | , typename N | |
| 14 | > | |
| 15 | struct advance | |
| 16 | { | |
| 17 | typedef |unspecified| type; | |
| 18 | }; | |
| 19 | ||
| 20 | ||
| 21 | ||
| 22 | Description | |
| 23 | ----------- | |
| 24 | ||
| 25 | Moves ``Iterator`` by the distance ``N``. For |bidirectional| and | |
| 26 | |random access| iterators, the distance may be negative. | |
| 27 | ||
| 28 | ||
| 29 | Header | |
| 30 | ------ | |
| 31 | ||
| 32 | .. parsed-literal:: | |
| 33 | ||
| 34 | #include <boost/mpl/advance.hpp> | |
| 35 | ||
| 36 | ||
| 37 | Parameters | |
| 38 | ---------- | |
| 39 | ||
| 40 | +---------------+---------------------------+-----------------------------------+ | |
| 41 | | Parameter | Requirement | Description | | |
| 42 | +===============+===========================+===================================+ | |
| 43 | | ``Iterator`` | |Forward Iterator| | An iterator to advance. | | |
| 44 | +---------------+---------------------------+-----------------------------------+ | |
| 45 | | ``N`` | |Integral Constant| | A distance. | | |
| 46 | +---------------+---------------------------+-----------------------------------+ | |
| 47 | ||
| 48 | ||
| 49 | Model Of | |
| 50 | -------- | |
| 51 | ||
| 52 | |Tag Dispatched Metafunction| | |
| 53 | ||
| 54 | ||
| 55 | Expression semantics | |
| 56 | -------------------- | |
| 57 | ||
| 58 | For a |Forward Iterator| ``iter`` and arbitrary |Integral Constant| ``n``: | |
| 59 | ||
| 60 | .. parsed-literal:: | |
| 61 | ||
| 62 | typedef advance<iter,n>::type j; | |
| 63 | ||
| 64 | :Return type: | |
| 65 | |Forward Iterator|. | |
| 66 | ||
| 67 | :Precondition: | |
| 68 | If ``Iterator`` is a |Forward Iterator|, ``n::value`` must be nonnegative. | |
| 69 | ||
| 70 | :Semantics: | |
| 71 | Equivalent to: | |
| 72 | ||
| 73 | .. parsed-literal:: | |
| 74 | ||
| 75 | typedef iter i0; | |
| 76 | typedef next<i0>::type i1; | |
| 77 | |...| | |
| 78 | typedef next<i\ *n-1*\ >::type j; | |
| 79 | ||
| 80 | if ``n::value > 0``, and | |
| 81 | ||
| 82 | .. parsed-literal:: | |
| 83 | ||
| 84 | typedef iter i0; | |
| 85 | typedef prior<i0>::type i1; | |
| 86 | |...| | |
| 87 | typedef prior<i\ *n-1*\ >::type j; | |
| 88 | ||
| 89 | otherwise. | |
| 90 | ||
| 91 | ||
| 92 | :Postcondition: | |
| 93 | ``j`` is dereferenceable or past-the-end; | |
| 94 | ``distance<iter,j>::value == n::value`` if ``n::value > 0``, and | |
| 95 | ``distance<j,iter>::value == n::value`` otherwise. | |
| 96 | ||
| 97 | ||
| 98 | Complexity | |
| 99 | ---------- | |
| 100 | ||
| 101 | Amortized constant time if ``iter`` is a model of | |
| 102 | |Random Access Iterator|, otherwise linear time. | |
| 103 | ||
| 104 | ||
| 105 | Example | |
| 106 | ------- | |
| 107 | ||
| 108 | .. parsed-literal:: | |
| 109 | ||
| 110 | typedef range_c<int,0,10> numbers; | |
| 111 | typedef begin<numbers>::type first; | |
| 112 | typedef end<numbers>::type last; | |
| 113 | ||
| 114 | typedef advance<first,int_<10> >::type i1; | |
| 115 | typedef advance<last,int_<-10> >::type i2; | |
| 116 | ||
| 117 | BOOST_MPL_ASSERT(( boost::is_same<i1,last> )); | |
| 118 | BOOST_MPL_ASSERT(( boost::is_same<i2,first> )); | |
| 119 | ||
| 120 | ||
| 121 | See also | |
| 122 | -------- | |
| 123 | ||
| 124 | |Iterators|, |Tag Dispatched Metafunction|, |distance|, |next| | |
| 125 | ||
| 126 | .. |bidirectional| replace:: `bidirectional`_ | |
| 127 | .. _bidirectional: `Bidirectional Iterator`_ | |
| 128 | .. |random access| replace:: `random access`_ | |
| 129 | .. _random access: `Random Access Iterator`_ | |
| 130 | ||
| 131 | ||
| 132 |