projects / ceph.git / blame
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| 7c673cae FG |
1 | .. Macros/Introspection//BOOST_MPL_HAS_XXX_TEMPLATE_DEF |
| 2 | ||
| 3 | .. Copyright Daniel Walker 2007. | |
| 4 | .. Distributed under the Boost | |
| 5 | .. Software License, Version 1.0. (See accompanying | |
| 6 | .. file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) | |
| 7 | ||
| 8 | BOOST_MPL_HAS_XXX_TEMPLATE_DEF | |
| 9 | ============================== | |
| 10 | ||
| 11 | Synopsis | |
| 12 | -------- | |
| 13 | ||
| 14 | .. parsed-literal:: | |
| 15 | ||
| 16 | #define BOOST_MPL_HAS_XXX_TEMPLATE_DEF(name) \\ | |
| 17 | |unspecified-token-seq| \\ | |
| 18 | /\*\*/ | |
| 19 | ||
| 20 | ||
| 21 | Description | |
| 22 | ----------- | |
| 23 | ||
| 24 | Expands into the definition of a boolean |Metafunction| ``has_name`` | |
| 25 | such that for any type ``x`` ``has_name<x>::value == true`` if and | |
| 26 | only if ``x`` is a class type and has a nested template member | |
| 27 | ``x::template name`` with no more than | |
| 28 | |BOOST_MPL_LIMIT_METAFUNCTION_ARITY| parameters. | |
| 29 | ||
| 30 | On deficient compilers not capable of performing the detection, | |
| 31 | ``has_name<x>::value`` is always ``false``. A boolean configuration | |
| 32 | macro, |BOOST_MPL_CFG_NO_HAS_XXX_TEMPLATE|, is provided to signal or | |
| 33 | override the "deficient" status of a particular compiler. | |
| 34 | ||
| 35 | |Note:| |BOOST_MPL_HAS_XXX_TEMPLATE_DEF| is a simplified front end to | |
| 36 | the |BOOST_MPL_HAS_XXX_TEMPLATE_NAMED_DEF| introspection macro |-- end | |
| 37 | note| | |
| 38 | ||
| 39 | ||
| 40 | Header | |
| 41 | ------ | |
| 42 | ||
| 43 | .. parsed-literal:: | |
| 44 | ||
| 45 | #include <boost/mpl/has_xxx.hpp> | |
| 46 | ||
| 47 | ||
| 48 | Parameters | |
| 49 | ---------- | |
| 50 | ||
| 51 | ||
| 52 | +---------------+-------------------------------+---------------------------------------------------+ | |
| 53 | | Parameter | Requirement | Description | | |
| 54 | +===============+===============================+===================================================+ | |
| 55 | | ``name`` | A legal identifier token | A name of the template member being detected. | | |
| 56 | +---------------+-------------------------------+---------------------------------------------------+ | |
| 57 | ||
| 58 | ||
| 59 | Expression semantics | |
| 60 | -------------------- | |
| 61 | ||
| 62 | For any legal C++ identifier ``name``: | |
| 63 | ||
| 64 | .. parsed-literal:: | |
| 65 | ||
| 66 | BOOST_MPL_HAS_XXX_TEMPLATE_DEF(name) | |
| 67 | ||
| 68 | :Precondition: | |
| 69 | Appears at namespace scope. | |
| 70 | ||
| 71 | :Return type: | |
| 72 | None. | |
| 73 | ||
| 74 | :Semantics: | |
| 75 | Equivalent to | |
| 76 | ||
| 77 | .. parsed-literal:: | |
| 78 | ||
| 79 | BOOST_MPL_HAS_XXX_TEMPLATE_NAMED_DEF( | |
| 80 | BOOST_PP_CAT(has\_,name), name, false | |
| 81 | ) | |
| 82 | ||
| 83 | ||
| 84 | Example | |
| 85 | ------- | |
| 86 | ||
| 87 | .. parsed-literal:: | |
| 88 | ||
| 89 | BOOST_MPL_HAS_XXX_TEMPLATE_DEF(xxx) | |
| 90 | ||
| 91 | struct test1 {}; | |
| 92 | struct test2 { void xxx(); }; | |
| 93 | struct test3 { int xxx; }; | |
| 94 | struct test4 { static int xxx(); }; | |
| 95 | struct test5 { typedef int xxx; }; | |
| 96 | struct test6 { struct xxx; }; | |
| 97 | struct test7 { typedef void (\*xxx)(); }; | |
| 98 | struct test8 { typedef void (xxx)(); }; | |
| 99 | struct test9 { template< class T > struct xxx {}; }; | |
| 100 | ||
| 101 | BOOST_MPL_ASSERT_NOT(( has_xxx<test1> )); | |
| 102 | BOOST_MPL_ASSERT_NOT(( has_xxx<test2> )); | |
| 103 | BOOST_MPL_ASSERT_NOT(( has_xxx<test3> )); | |
| 104 | BOOST_MPL_ASSERT_NOT(( has_xxx<test4> )); | |
| 105 | BOOST_MPL_ASSERT_NOT(( has_xxx<test5> )); | |
| 106 | BOOST_MPL_ASSERT_NOT(( has_xxx<test6> )); | |
| 107 | BOOST_MPL_ASSERT_NOT(( has_xxx<test7> )); | |
| 108 | BOOST_MPL_ASSERT_NOT(( has_xxx<test8> )); | |
| 109 | ||
| 110 | #if !defined(BOOST_MPL_CFG_NO_HAS_XXX_TEMPLATE) | |
| 111 | BOOST_MPL_ASSERT(( has_xxx<test9> )); | |
| 112 | #endif | |
| 113 | ||
| 114 | BOOST_MPL_ASSERT(( has_xxx<test9, true\_> )); | |
| 115 | ||
| 116 | ||
| 117 | See also | |
| 118 | -------- | |
| 119 | ||
| 120 | |Macros|, |BOOST_MPL_HAS_XXX_TEMPLATE_NAMED_DEF|, | |
| 121 | |BOOST_MPL_CFG_NO_HAS_XXX_TEMPLATE|, |BOOST_MPL_LIMIT_METAFUNCTION_ARITY| | |
| 122 |