projects / ceph.git / blame
| Commit | Line | Data |
|---|---|---|
| 7c673cae FG |
1 | .. .. Algorithms/Iteration Algorithms |
| 2 | ||
| 3 | .. UNFINISHED: Expression semantics and everything that follows | |
| 4 | ||
| 5 | ||
| 6 | iter_fold_if | |
| 7 | ============ | |
| 8 | ||
| 9 | Synopsis | |
| 10 | -------- | |
| 11 | ||
| 12 | .. parsed-literal:: | |
| 13 | ||
| 14 | template< | |
| 15 | typename Sequence | |
| 16 | , typename State | |
| 17 | , typename ForwardOp | |
| 18 | , typename ForwardPred | |
| 19 | , typename BackwardOp = |unspecified| | |
| 20 | , typename BackwardPred = |unspecified| | |
| 21 | > | |
| 22 | struct iter_fold_if | |
| 23 | { | |
| 24 | typedef |unspecified| type; | |
| 25 | }; | |
| 26 | ||
| 27 | ||
| 28 | Description | |
| 29 | ----------- | |
| 30 | ||
| 31 | Returns the result of the successive application of binary ``ForwardOp`` to the result | |
| 32 | of the previous ``ForwardOp`` invocation (``State`` if it's the first call) and each | |
| 33 | iterator in the sequence range determined by ``ForwardPred`` predicate. If ``BackwardOp`` | |
| 34 | is provided, it's similarly applied on backward traversal to the result of the | |
| 35 | previous ``BackwardOp`` invocation (the last result returned by ``ForwardOp` if it's | |
| 36 | the first call) and each iterator in the sequence range determined by | |
| 37 | ``BackwardPred`` predicate. | |
| 38 | ||
| 39 | ||
| 40 | Header | |
| 41 | ------ | |
| 42 | ||
| 43 | .. parsed-literal:: | |
| 44 | ||
| 45 | #include <boost/mpl/iter_fold_if.hpp> | |
| 46 | ||
| 47 | ||
| 48 | Parameters | |
| 49 | ---------- | |
| 50 | ||
| 51 | +-------------------+-------------------------------+-----------------------------------------------+ | |
| 52 | | Parameter | Requirement | Description | | |
| 53 | +===============+===================================+===============================================+ | |
| 54 | | ``Sequence`` | |Forward Sequence| | A sequence to iterate. | | |
| 55 | +-------------------+-------------------------------+-----------------------------------------------+ | |
| 56 | | ``State`` | Any type | The initial state for the first ``BackwardOp``| | |
| 57 | | | | / ``ForwardOp`` application. | | |
| 58 | +-------------------+-------------------------------+-----------------------------------------------+ | |
| 59 | | ``ForwardOp`` | Binary |Lambda Expression| | The operation to be executed on forward | | |
| 60 | | | | traversal. | | |
| 61 | +-------------------+-------------------------------+-----------------------------------------------+ | |
| 62 | | ``ForwardPred`` | Binary |Lambda Expression| | The forward traversal predicate. | | |
| 63 | +-------------------+-------------------------------+-----------------------------------------------+ | |
| 64 | | ``BackwardOp`` | Binary |Lambda Expression| | The operation to be executed on backward | | |
| 65 | | | | traversal. | | |
| 66 | +-------------------+-------------------------------+-----------------------------------------------+ | |
| 67 | | ``BackwardPred`` | Binary |Lambda Expression| | The backward traversal predicate. | | |
| 68 | +-------------------+-------------------------------+-----------------------------------------------+ | |
| 69 | ||
| 70 | ||
| 71 | Expression semantics | |
| 72 | -------------------- | |
| 73 | ||
| 74 | For any |Forward Sequence| ``s``, binary |Lambda Expression| ``op``, and an | |
| 75 | arbitrary type ``state``: | |
| 76 | ||
| 77 | ||
| 78 | .. parsed-literal:: | |
| 79 | ||
| 80 | typedef iter_fold<Sequence,T,Op>::type t; | |
| 81 | ||
| 82 | :Return type: | |
| 83 | A type | |
| 84 | ||
| 85 | :Semantics: | |
| 86 | Equivalent to | |
| 87 | ||
| 88 | .. parsed-literal:: | |
| 89 | ||
| 90 | typedef lambda<Op>::type op; | |
| 91 | typedef begin<Sequence>::type i1; | |
| 92 | typedef apply<op,T,i1>::type t1; | |
| 93 | typedef i1::next i2; | |
| 94 | typedef apply<op,t1,i2>::type t2; | |
| 95 | ... | |
| 96 | typedef apply<op,T,in>::type tn; | |
| 97 | typedef in::next last; | |
| 98 | typedef tn t | |
| 99 | ||
| 100 | where ``n == size<Sequence>::value`` and ``last`` is identical to ``end<Sequence>::type``; | |
| 101 | ||
| 102 | Equivalent to ``typedef T t;`` if the sequence is empty. | |
| 103 | ||
| 104 | ||
| 105 | ||
| 106 | Complexity | |
| 107 | ---------- | |
| 108 | ||
| 109 | Linear. Exactly ``size<Sequence>::value`` applications of ``ForwardOp``. | |
| 110 | ||
| 111 | ||
| 112 | Example | |
| 113 | ------- | |
| 114 | ||
| 115 | .. parsed-literal:: | |
| 116 | ||
| 117 | typedef list_c<int,5,-1,0,7,2,0,-5,4> numbers; | |
| 118 | typedef iter_fold< | |
| 119 | numbers | |
| 120 | , begin<numbers>::type | |
| 121 | , if_< less< deref<_1>, deref<_2> >,_2,_1 > | |
| 122 | >::type max_element_iter; | |
| 123 | ||
| 124 | BOOST_STATIC_ASSERT(max_element_iter::type::value == 7); | |
| 125 | ||
| 126 | ||
| 127 | ||
| 128 | See also | |
| 129 | -------- | |
| 130 | ||
| 131 | Algorithms, ``iter_fold_backward``, ``fold``, ``fold_backward``, ``copy``, ``copy_backward`` | |
| 132 | ||
| 133 | ||
| 134 |