projects / ceph.git / blame
| Commit | Line | Data |
|---|---|---|
| 7c673cae FG |
1 | .. Iterators/Iterator Metafunctions//iterator_category |60 |
| 2 | ||
| 3 | iterator_category | |
| 4 | ================= | |
| 5 | ||
| 6 | Synopsis | |
| 7 | -------- | |
| 8 | ||
| 9 | .. parsed-literal:: | |
| 10 | ||
| 11 | template< | |
| 12 | typename Iterator | |
| 13 | > | |
| 14 | struct iterator_category | |
| 15 | { | |
| 16 | typedef typename Iterator::category type; | |
| 17 | }; | |
| 18 | ||
| 19 | ||
| 20 | ||
| 21 | Description | |
| 22 | ----------- | |
| 23 | ||
| 24 | Returns one of the following iterator category tags: | |
| 25 | ||
| 26 | * ``forward_iterator_tag`` | |
| 27 | * ``bidirectional_iterator_tag`` | |
| 28 | * ``random_access_iterator_tag`` | |
| 29 | ||
| 30 | ||
| 31 | Header | |
| 32 | ------ | |
| 33 | ||
| 34 | .. parsed-literal:: | |
| 35 | ||
| 36 | #include <boost/mpl/iterator_category.hpp> | |
| 37 | #include <boost/mpl/iterator_tags.hpp> | |
| 38 | ||
| 39 | ||
| 40 | Parameters | |
| 41 | ---------- | |
| 42 | ||
| 43 | +---------------+-----------------------+-------------------------------------------+ | |
| 44 | | Parameter | Requirement | Description | | |
| 45 | +===============+=======================+===========================================+ | |
| 46 | | ``Iterator`` | |Forward Iterator| | The iterator to obtain a category for. | | |
| 47 | +---------------+-----------------------+-------------------------------------------+ | |
| 48 | ||
| 49 | ||
| 50 | Expression semantics | |
| 51 | -------------------- | |
| 52 | ||
| 53 | For any |Forward Iterator|\ s ``iter``: | |
| 54 | ||
| 55 | ||
| 56 | .. parsed-literal:: | |
| 57 | ||
| 58 | typedef iterator_category<iter>::type tag; | |
| 59 | ||
| 60 | :Return type: | |
| 61 | |Integral Constant|. | |
| 62 | ||
| 63 | :Semantics: | |
| 64 | ``tag`` is ``forward_iterator_tag`` if ``iter`` is a model of |Forward Iterator|, | |
| 65 | ``bidirectional_iterator_tag`` if ``iter`` is a model of |Bidirectional Iterator|, | |
| 66 | or ``random_access_iterator_tag`` if ``iter`` is a model of |Random Access Iterator|; | |
| 67 | ||
| 68 | :Postcondition: | |
| 69 | ``forward_iterator_tag::value < bidirectional_iterator_tag::value``, | |
| 70 | ``bidirectional_iterator_tag::value < random_access_iterator_tag::value``. | |
| 71 | ||
| 72 | ||
| 73 | Complexity | |
| 74 | ---------- | |
| 75 | ||
| 76 | Amortized constant time. | |
| 77 | ||
| 78 | ||
| 79 | Example | |
| 80 | ------- | |
| 81 | ||
| 82 | .. parsed-literal:: | |
| 83 | ||
| 84 | template< typename Tag, typename Iterator > | |
| 85 | struct algorithm_impl | |
| 86 | { | |
| 87 | // *O(n)* implementation | |
| 88 | }; | |
| 89 | ||
| 90 | template< typename Iterator > | |
| 91 | struct algorithm_impl<random_access_iterator_tag,Iterator> | |
| 92 | { | |
| 93 | // *O(1)* implementation | |
| 94 | }; | |
| 95 | ||
| 96 | template< typename Iterator > | |
| 97 | struct algorithm | |
| 98 | : algorithm_impl< | |
| 99 | iterator_category<Iterator>::type | |
| 100 | , Iterator | |
| 101 | > | |
| 102 | { | |
| 103 | }; | |
| 104 | ||
| 105 | ||
| 106 | ||
| 107 | See also | |
| 108 | -------- | |
| 109 | ||
| 110 | |Iterators|, |begin| / |end|, |advance|, |distance|, |next| | |
| 111 | ||
| 112 | ||
| 113 |