projects / ceph.git / blame
| Commit | Line | Data |
|---|---|---|
| 7c673cae FG |
1 | .. Metafunctions/Composition and Argument Binding//quote |40 |
| 2 | ||
| 3 | quote | |
| 4 | ===== | |
| 5 | ||
| 6 | Synopsis | |
| 7 | -------- | |
| 8 | ||
| 9 | .. parsed-literal:: | |
| 10 | ||
| 11 | template< | |
| 12 | template< typename P1 > class F | |
| 13 | , typename Tag = |unspecified| | |
| 14 | > | |
| 15 | struct quote1 | |
| 16 | { | |
| 17 | // |unspecified| | |
| 18 | // |...| | |
| 19 | }; | |
| 20 | ||
| 21 | |...| | |
| 22 | ||
| 23 | template< | |
| 24 | template< typename P1,\ |...| typename P\ *n* > class F | |
| 25 | , typename Tag = |unspecified| | |
| 26 | > | |
| 27 | struct quote\ *n* | |
| 28 | { | |
| 29 | // |unspecified| | |
| 30 | // |...| | |
| 31 | }; | |
| 32 | ||
| 33 | ||
| 34 | Description | |
| 35 | ----------- | |
| 36 | ||
| 37 | ``quote``\ *n* is a higher-order primitive that wraps an *n*-ary |Metafunction| to create | |
| 38 | a corresponding |Metafunction Class|. | |
| 39 | ||
| 40 | ||
| 41 | Header | |
| 42 | ------ | |
| 43 | ||
| 44 | .. parsed-literal:: | |
| 45 | ||
| 46 | #include <boost/mpl/quote.hpp> | |
| 47 | ||
| 48 | ||
| 49 | Model of | |
| 50 | -------- | |
| 51 | ||
| 52 | |Metafunction Class| | |
| 53 | ||
| 54 | ||
| 55 | Parameters | |
| 56 | ---------- | |
| 57 | ||
| 58 | +---------------+-----------------------+-----------------------------------------------+ | |
| 59 | | Parameter | Requirement | Description | | |
| 60 | +===============+=======================+===============================================+ | |
| 61 | | ``F`` | |Metafunction| | A metafunction to wrap. | | |
| 62 | +---------------+-----------------------+-----------------------------------------------+ | |
| 63 | | ``Tag`` | Any type | A tag determining wrap semantics. | | |
| 64 | +---------------+-----------------------+-----------------------------------------------+ | |
| 65 | ||
| 66 | ||
| 67 | Expression semantics | |
| 68 | -------------------- | |
| 69 | ||
| 70 | For any *n*-ary |Metafunction| ``f`` and arbitrary type ``tag``: | |
| 71 | ||
| 72 | ||
| 73 | .. parsed-literal:: | |
| 74 | ||
| 75 | typedef quote\ *n*\ <f> g; | |
| 76 | typedef quote\ *n*\ <f,tag> g; | |
| 77 | ||
| 78 | :Return type: | |
| 79 | |Metafunction Class| | |
| 80 | ||
| 81 | :Semantics: | |
| 82 | Equivalent to | |
| 83 | ||
| 84 | .. parsed-literal:: | |
| 85 | ||
| 86 | struct g | |
| 87 | { | |
| 88 | template< typename A1,\ |...| typename A\ *n* > struct apply | |
| 89 | : f<A1,\ |...|\ A\ *n*\ > | |
| 90 | { | |
| 91 | }; | |
| 92 | }; | |
| 93 | ||
| 94 | if ``f<A1,...An>`` has a nested type member ``::type``, and to | |
| 95 | ||
| 96 | .. parsed-literal:: | |
| 97 | ||
| 98 | struct g | |
| 99 | { | |
| 100 | template< typename A1,\ |...| typename A\ *n* > struct apply | |
| 101 | { | |
| 102 | typedef f<A1,\ |...|\ A\ *n*\ > type; | |
| 103 | }; | |
| 104 | }; | |
| 105 | ||
| 106 | otherwise. | |
| 107 | ||
| 108 | ||
| 109 | Example | |
| 110 | ------- | |
| 111 | ||
| 112 | .. parsed-literal:: | |
| 113 | ||
| 114 | template< typename T > struct f1 | |
| 115 | { | |
| 116 | typedef T type; | |
| 117 | }; | |
| 118 | ||
| 119 | template< | |
| 120 | typename T1, typename T2, typename T3, typename T4, typename T5 | |
| 121 | > | |
| 122 | struct f5 | |
| 123 | { | |
| 124 | // no 'type' member! | |
| 125 | }; | |
| 126 | ||
| 127 | typedef quote\ ``1``\<f1>::apply<int>::type t1; | |
| 128 | typedef quote\ ``5``\<f5>::apply<char,short,int,long,float>::type t5; | |
| 129 | ||
| 130 | BOOST_MPL_ASSERT(( is_same< t1, int > )); | |
| 131 | BOOST_MPL_ASSERT(( is_same< t5, f5<char,short,int,long,float> > )); | |
| 132 | ||
| 133 | ||
| 134 | See also | |
| 135 | -------- | |
| 136 | ||
| 137 | |Composition and Argument Binding|, |Invocation|, |bind|, |lambda|, |protect|, |apply| | |
| 138 | ||
| 139 | ||
| 140 |