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