projects / ceph.git / blame
| Commit | Line | Data |
|---|---|---|
| 7c673cae FG |
1 | .. Algorithms/Runtime Algorithms//for_each |10 |
| 2 | ||
| 3 | for_each | |
| 4 | ======== | |
| 5 | ||
| 6 | Synopsis | |
| 7 | -------- | |
| 8 | ||
| 9 | .. parsed-literal:: | |
| 10 | ||
| 11 | template< | |
| 12 | typename Sequence | |
| 13 | , typename F | |
| 14 | > | |
| 15 | void for_each( F f ); | |
| 16 | ||
| 17 | template< | |
| 18 | typename Sequence | |
| 19 | , typename TransformOp | |
| 20 | , typename F | |
| 21 | > | |
| 22 | void for_each( F f ); | |
| 23 | ||
| 24 | ||
| 25 | Description | |
| 26 | ----------- | |
| 27 | ||
| 28 | ``for_each`` is a family of overloaded function templates: | |
| 29 | ||
| 30 | * ``for_each<Sequence>( f )`` applies the runtime function object | |
| 31 | ``f`` to every element in the |begin/end<Sequence>| range. | |
| 32 | ||
| 33 | * ``for_each<Sequence,TransformOp>( f )`` applies the runtime function | |
| 34 | object ``f`` to the result of the transformation ``TransformOp`` of | |
| 35 | every element in the |begin/end<Sequence>| range. | |
| 36 | ||
| 37 | ||
| 38 | Header | |
| 39 | ------ | |
| 40 | ||
| 41 | .. parsed-literal:: | |
| 42 | ||
| 43 | #include <boost/mpl/for_each.hpp> | |
| 44 | ||
| 45 | ||
| 46 | Parameters | |
| 47 | ---------- | |
| 48 | ||
| 49 | +-------------------+-----------------------------------+-----------------------------------+ | |
| 50 | | Parameter | Requirement | Description | | |
| 51 | +===================+===================================+===================================+ | |
| 52 | | ``Sequence`` | |Forward Sequence| | A sequence to iterate. | | |
| 53 | +-------------------+-----------------------------------+-----------------------------------+ | |
| 54 | | ``TransformOp`` | |Lambda Expression| | A transformation. | | |
| 55 | +-------------------+-----------------------------------+-----------------------------------+ | |
| 56 | | ``f`` | An |unary function object| | A runtime operation to apply. | | |
| 57 | +-------------------+-----------------------------------+-----------------------------------+ | |
| 58 | ||
| 59 | ||
| 60 | Expression semantics | |
| 61 | -------------------- | |
| 62 | ||
| 63 | For any |Forward Sequence| ``s``, |Lambda Expression| ``op`` , and an | |
| 64 | |unary function object| ``f``: | |
| 65 | ||
| 66 | .. parsed-literal:: | |
| 67 | ||
| 68 | for_each<s>( f ); | |
| 69 | ||
| 70 | :Return type: | |
| 71 | ``void`` | |
| 72 | ||
| 73 | :Postcondition: | |
| 74 | Equivalent to | |
| 75 | ||
| 76 | .. parsed-literal:: | |
| 77 | ||
| 78 | typedef begin<Sequence>::type i\ :sub:`1`; | |
| 79 | |value_initialized|\ < deref<i\ :sub:`1`>::type > x\ :sub:`1`; | |
| 80 | f(boost::get(x\ :sub:`1`)); | |
| 81 | ||
| 82 | typedef next<i\ :sub:`1`>::type i\ :sub:`2`; | |
| 83 | |value_initialized|\ < deref<i\ :sub:`2`>::type > x\ :sub:`2`; | |
| 84 | f(boost::get(x\ :sub:`2`)); | |
| 85 | |...| | |
| 86 | |value_initialized|\ < deref<i\ :sub:`n`>::type > x\ :sub:`n`; | |
| 87 | f(boost::get(x\ :sub:`n`)); | |
| 88 | typedef next<i\ :sub:`n`>::type last; | |
| 89 | ||
| 90 | where ``n == size<s>::value`` and ``last`` is identical to | |
| 91 | ``end<s>::type``; no effect if ``empty<s>::value == true``. | |
| 92 | ||
| 93 | ||
| 94 | .. parsed-literal:: | |
| 95 | ||
| 96 | for_each<s,op>( f ); | |
| 97 | ||
| 98 | :Return type: | |
| 99 | ``void`` | |
| 100 | ||
| 101 | :Postcondition: | |
| 102 | Equivalent to | |
| 103 | ||
| 104 | .. parsed-literal:: | |
| 105 | ||
| 106 | for_each< transform_view<s,op> >( f ); | |
| 107 | ||
| 108 | ||
| 109 | Complexity | |
| 110 | ---------- | |
| 111 | ||
| 112 | Linear. Exactly ``size<s>::value`` applications of ``op`` and ``f``. | |
| 113 | ||
| 114 | ||
| 115 | Example | |
| 116 | ------- | |
| 117 | ||
| 118 | .. parsed-literal:: | |
| 119 | ||
| 120 | struct value_printer | |
| 121 | { | |
| 122 | template< typename U > void operator()(U x) | |
| 123 | { | |
| 124 | std::cout << x << '\\n'; | |
| 125 | } | |
| 126 | }; | |
| 127 | ||
| 128 | int main() | |
| 129 | { | |
| 130 | for_each< range_c<int,0,10> >( value_printer() ); | |
| 131 | } | |
| 132 | ||
| 133 | ||
| 134 | See also | |
| 135 | -------- | |
| 136 | ||
| 137 | |Runtime Algorithms|, |Views|, |transform_view| | |
| 138 | ||
| 139 | .. |unary function object| replace:: `unary function object <http://www.sgi.com/tech/stl/UnaryFunction.html>`__ | |
| 140 | .. |value_initialized| replace:: `value_initialized <http://www.boost.org/libs/utility/value_init.htm>`__ | |
| 141 | ||
| 142 | ||
| 143 |