projects / ceph.git / blame
| Commit | Line | Data |
|---|---|---|
| 7c673cae FG |
1 | .. Iterators/Iterator Metafunctions//distance |20 |
| 2 | ||
| 3 | distance | |
| 4 | ======== | |
| 5 | ||
| 6 | Synopsis | |
| 7 | -------- | |
| 8 | ||
| 9 | .. parsed-literal:: | |
| 10 | ||
| 11 | template< | |
| 12 | typename First | |
| 13 | , typename Last | |
| 14 | > | |
| 15 | struct distance | |
| 16 | { | |
| 17 | typedef |unspecified| type; | |
| 18 | }; | |
| 19 | ||
| 20 | ||
| 21 | ||
| 22 | Description | |
| 23 | ----------- | |
| 24 | ||
| 25 | Returns the distance between ``First`` and ``Last`` iterators, that is, an | |
| 26 | |Integral Constant| ``n`` such that ``advance<First,n>::type`` is | |
| 27 | identical to ``Last``. | |
| 28 | ||
| 29 | ||
| 30 | Header | |
| 31 | ------ | |
| 32 | ||
| 33 | .. parsed-literal:: | |
| 34 | ||
| 35 | #include <boost/mpl/distance.hpp> | |
| 36 | ||
| 37 | ||
| 38 | Parameters | |
| 39 | ---------- | |
| 40 | ||
| 41 | +---------------+---------------------------+-----------------------------------+ | |
| 42 | | Parameter | Requirement | Description | | |
| 43 | +===============+===========================+===================================+ | |
| 44 | | ``First``, | |Forward Iterator| | Iterators to compute a | | |
| 45 | | ``Last`` | | distance between. | | |
| 46 | +---------------+---------------------------+-----------------------------------+ | |
| 47 | ||
| 48 | Model Of | |
| 49 | -------- | |
| 50 | ||
| 51 | |Tag Dispatched Metafunction| | |
| 52 | ||
| 53 | ||
| 54 | Expression semantics | |
| 55 | -------------------- | |
| 56 | ||
| 57 | For any |Forward Iterator|\ s ``first`` and ``last``: | |
| 58 | ||
| 59 | .. parsed-literal:: | |
| 60 | ||
| 61 | typedef distance<first,last>::type n; | |
| 62 | ||
| 63 | :Return type: | |
| 64 | |Integral Constant|. | |
| 65 | ||
| 66 | :Precondition: | |
| 67 | [``first``, ``last``) is a valid range. | |
| 68 | ||
| 69 | :Semantics: | |
| 70 | Equivalent to | |
| 71 | ||
| 72 | .. parsed-literal:: | |
| 73 | ||
| 74 | typedef iter_fold< | |
| 75 | iterator_range<first,last> | |
| 76 | , long_<0> | |
| 77 | , next<_1> | |
| 78 | >::type n; | |
| 79 | ||
| 80 | ||
| 81 | :Postcondition: | |
| 82 | ``is_same< advance<first,n>::type, last >::value == true``. | |
| 83 | ||
| 84 | ||
| 85 | Complexity | |
| 86 | ---------- | |
| 87 | ||
| 88 | Amortized constant time if ``first`` and ``last`` are |Random Access Iterator|\ s, | |
| 89 | otherwise linear time. | |
| 90 | ||
| 91 | ||
| 92 | Example | |
| 93 | ------- | |
| 94 | ||
| 95 | .. parsed-literal:: | |
| 96 | ||
| 97 | typedef range_c<int,0,10>::type range; | |
| 98 | typedef begin<range>::type first; | |
| 99 | typedef end<range>::type last; | |
| 100 | ||
| 101 | BOOST_MPL_ASSERT_RELATION( (distance<first,last>::value), ==, 10); | |
| 102 | ||
| 103 | ||
| 104 | See also | |
| 105 | -------- | |
| 106 | ||
| 107 | |Iterators|, |Tag Dispatched Metafunction|, |advance|, |next|, |prior| | |
| 108 | ||
| 109 | ||
| 110 |