projects / ceph.git / blame
| Commit | Line | Data |
|---|---|---|
| 7c673cae FG |
1 | .. Macros/Introspection//BOOST_MPL_HAS_XXX_TRAIT_DEF |
| 2 | ||
| 3 | BOOST_MPL_HAS_XXX_TRAIT_DEF | |
| 4 | =========================== | |
| 5 | ||
| 6 | Synopsis | |
| 7 | -------- | |
| 8 | ||
| 9 | .. parsed-literal:: | |
| 10 | ||
| 11 | #define BOOST_MPL_HAS_XXX_TRAIT_DEF(name) \\ | |
| 12 | |unspecified-token-seq| \\ | |
| 13 | /\*\*/ | |
| 14 | ||
| 15 | ||
| 16 | Description | |
| 17 | ----------- | |
| 18 | ||
| 19 | Expands into a definition of a boolean unary |Metafunction| ``has_name`` | |
| 20 | such that for any type ``x`` ``has_name<x>::value == true`` if and only | |
| 21 | if ``x`` is a class type and has a nested type memeber ``x::name``. | |
| 22 | ||
| 23 | On the deficient compilers not capabale of performing the detection, | |
| 24 | ``has_name<x>::value`` always returns ``false``. A boolean configuraion | |
| 25 | macro, |BOOST_MPL_CFG_NO_HAS_XXX|, is provided to signal or override | |
| 26 | the "deficient" status of a particular compiler. | |
| 27 | ||
| 28 | |Note:| |BOOST_MPL_HAS_XXX_TRAIT_DEF| is a simplified front end to | |
| 29 | the |BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF| introspection macro |-- end note| | |
| 30 | ||
| 31 | ||
| 32 | Header | |
| 33 | ------ | |
| 34 | ||
| 35 | .. parsed-literal:: | |
| 36 | ||
| 37 | #include <boost/mpl/has_xxx.hpp> | |
| 38 | ||
| 39 | ||
| 40 | Parameters | |
| 41 | ---------- | |
| 42 | ||
| 43 | ||
| 44 | +---------------+-------------------------------+---------------------------------------------------+ | |
| 45 | | Parameter | Requirement | Description | | |
| 46 | +===============+===============================+===================================================+ | |
| 47 | | ``name`` | A legal identifier token | A name of the member being detected. | | |
| 48 | +---------------+-------------------------------+---------------------------------------------------+ | |
| 49 | ||
| 50 | ||
| 51 | Expression semantics | |
| 52 | -------------------- | |
| 53 | ||
| 54 | For any legal C++ identifier ``name``: | |
| 55 | ||
| 56 | .. parsed-literal:: | |
| 57 | ||
| 58 | BOOST_MPL_HAS_XXX_TRAIT_DEF(name) | |
| 59 | ||
| 60 | :Precondition: | |
| 61 | Appears at namespace scope. | |
| 62 | ||
| 63 | :Return type: | |
| 64 | None. | |
| 65 | ||
| 66 | :Semantics: | |
| 67 | Equivalent to | |
| 68 | ||
| 69 | .. parsed-literal:: | |
| 70 | ||
| 71 | BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF( | |
| 72 | BOOST_PP_CAT(has\_,name), name, false | |
| 73 | ) | |
| 74 | ||
| 75 | ||
| 76 | Example | |
| 77 | ------- | |
| 78 | ||
| 79 | .. parsed-literal:: | |
| 80 | ||
| 81 | BOOST_MPL_HAS_XXX_TRAIT_DEF(xxx) | |
| 82 | ||
| 83 | struct test1 {}; | |
| 84 | struct test2 { void xxx(); }; | |
| 85 | struct test3 { int xxx; }; | |
| 86 | struct test4 { static int xxx(); }; | |
| 87 | struct test5 { template< typename T > struct xxx {}; }; | |
| 88 | struct test6 { typedef int xxx; }; | |
| 89 | struct test7 { struct xxx; }; | |
| 90 | struct test8 { typedef void (\*xxx)(); }; | |
| 91 | struct test9 { typedef void (xxx)(); }; | |
| 92 | ||
| 93 | BOOST_MPL_ASSERT_NOT(( has_xxx<test1> )); | |
| 94 | BOOST_MPL_ASSERT_NOT(( has_xxx<test2> )); | |
| 95 | BOOST_MPL_ASSERT_NOT(( has_xxx<test3> )); | |
| 96 | BOOST_MPL_ASSERT_NOT(( has_xxx<test4> )); | |
| 97 | BOOST_MPL_ASSERT_NOT(( has_xxx<test5> )); | |
| 98 | ||
| 99 | #if !defined(BOOST_MPL_CFG_NO_HAS_XXX) | |
| 100 | BOOST_MPL_ASSERT(( has_xxx<test6> )); | |
| 101 | BOOST_MPL_ASSERT(( has_xxx<test7> )); | |
| 102 | BOOST_MPL_ASSERT(( has_xxx<test8> )); | |
| 103 | BOOST_MPL_ASSERT(( has_xxx<test9> )); | |
| 104 | #endif | |
| 105 | ||
| 106 | BOOST_MPL_ASSERT(( has_xxx<test6,true\_> )); | |
| 107 | BOOST_MPL_ASSERT(( has_xxx<test7,true\_> )); | |
| 108 | BOOST_MPL_ASSERT(( has_xxx<test8,true\_> )); | |
| 109 | BOOST_MPL_ASSERT(( has_xxx<test9,true\_> )); | |
| 110 | ||
| 111 | ||
| 112 | See also | |
| 113 | -------- | |
| 114 | ||
| 115 | |Macros|, |BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF|, |BOOST_MPL_CFG_NO_HAS_XXX| | |
| 116 | ||
| 117 | ||
| 118 |