projects / ceph.git / blame
| Commit | Line | Data |
|---|---|---|
| 7c673cae FG |
1 | .. Metafunctions/Miscellaneous//inherit_linearly |40 |
| 2 | ||
| 3 | inherit_linearly | |
| 4 | ================ | |
| 5 | ||
| 6 | Synopsis | |
| 7 | -------- | |
| 8 | ||
| 9 | .. parsed-literal:: | |
| 10 | ||
| 11 | template< | |
| 12 | typename Types | |
| 13 | , typename Node | |
| 14 | , typename Root = empty_base | |
| 15 | > | |
| 16 | struct inherit_linearly | |
| 17 | : fold<Types,Root,Node> | |
| 18 | { | |
| 19 | }; | |
| 20 | ||
| 21 | ||
| 22 | Description | |
| 23 | ----------- | |
| 24 | ||
| 25 | A convenience wrapper for ``fold`` to use in the context of sequence-driven | |
| 26 | class composition. Returns the result the successive application of binary | |
| 27 | ``Node`` to the result of the previous ``Node`` invocation (``Root`` if it's | |
| 28 | the first call) and every type in the |Forward Sequence| ``Types`` in order. | |
| 29 | ||
| 30 | ||
| 31 | Header | |
| 32 | ------ | |
| 33 | ||
| 34 | .. parsed-literal:: | |
| 35 | ||
| 36 | #include <boost/mpl/inherit_linearly.hpp> | |
| 37 | ||
| 38 | ||
| 39 | Model of | |
| 40 | -------- | |
| 41 | ||
| 42 | |Metafunction| | |
| 43 | ||
| 44 | ||
| 45 | Parameters | |
| 46 | ---------- | |
| 47 | ||
| 48 | +---------------+-------------------------------+---------------------------------------------------+ | |
| 49 | | Parameter | Requirement | Description | | |
| 50 | +===============+===============================+===================================================+ | |
| 51 | | ``Types`` | |Forward Sequence| | Types to inherit from. | | |
| 52 | +---------------+-------------------------------+---------------------------------------------------+ | |
| 53 | | ``Node`` | Binary |Lambda Expression| | A derivation metafunction. | | |
| 54 | +---------------+-------------------------------+---------------------------------------------------+ | |
| 55 | | ``Root`` | A class type | A type to be placed at the root of the class | | |
| 56 | | | | hierarchy. | | |
| 57 | +---------------+-------------------------------+---------------------------------------------------+ | |
| 58 | ||
| 59 | ||
| 60 | Expression semantics | |
| 61 | -------------------- | |
| 62 | ||
| 63 | For any |Forward Sequence| ``types``, binary |Lambda Expression| ``node``, and arbitrary | |
| 64 | class type ``root``: | |
| 65 | ||
| 66 | ||
| 67 | .. parsed-literal:: | |
| 68 | ||
| 69 | typedef inherit_linearly<types,node,root>::type r; | |
| 70 | ||
| 71 | :Return type: | |
| 72 | A class type. | |
| 73 | ||
| 74 | :Semantics: | |
| 75 | Equivalent to | |
| 76 | ||
| 77 | .. parsed-literal:: | |
| 78 | ||
| 79 | typedef fold<types,root,node>::type r; | |
| 80 | ||
| 81 | ||
| 82 | ||
| 83 | Complexity | |
| 84 | ---------- | |
| 85 | ||
| 86 | Linear. Exactly ``size<types>::value`` applications of ``node``. | |
| 87 | ||
| 88 | ||
| 89 | Example | |
| 90 | ------- | |
| 91 | ||
| 92 | .. parsed-literal:: | |
| 93 | ||
| 94 | template< typename T > struct tuple_field | |
| 95 | { | |
| 96 | T field; | |
| 97 | }; | |
| 98 | ||
| 99 | template< typename T > | |
| 100 | inline | |
| 101 | T& field(tuple_field<T>& t) | |
| 102 | { | |
| 103 | return t.field; | |
| 104 | } | |
| 105 | ||
| 106 | typedef inherit_linearly< | |
| 107 | vector<int,char const*,bool> | |
| 108 | , inherit< _1, tuple_field<_2> > | |
| 109 | >::type tuple; | |
| 110 | ||
| 111 | ||
| 112 | int main() | |
| 113 | { | |
| 114 | tuple t; | |
| 115 | ||
| 116 | field<int>(t) = -1; | |
| 117 | field<char const*>(t) = "text"; | |
| 118 | field<bool>(t) = false; | |
| 119 | ||
| 120 | std::cout | |
| 121 | << field<int>(t) << '\n' | |
| 122 | << field<char const*>(t) << '\n' | |
| 123 | << field<bool>(t) << '\n' | |
| 124 | ; | |
| 125 | } | |
| 126 | ||
| 127 | ||
| 128 | See also | |
| 129 | -------- | |
| 130 | ||
| 131 | |Metafunctions|, |Algorithms|, |inherit|, |empty_base|, |fold|, |reverse_fold| | |
| 132 | ||
| 133 | ||
| 134 |