projects / ceph.git / blame
| Commit | Line | Data |
|---|---|---|
| 7c673cae FG |
1 | .. Metafunctions/Logical Operations//and_ |10 |
| 2 | ||
| 3 | and\_ | |
| 4 | ===== | |
| 5 | ||
| 6 | Synopsis | |
| 7 | -------- | |
| 8 | ||
| 9 | .. parsed-literal:: | |
| 10 | ||
| 11 | template< | |
| 12 | typename F1 | |
| 13 | , typename F2 | |
| 14 | |...| | |
| 15 | , typename F\ *n* = |unspecified| | |
| 16 | > | |
| 17 | struct and\_ | |
| 18 | { | |
| 19 | typedef |unspecified| type; | |
| 20 | }; | |
| 21 | ||
| 22 | ||
| 23 | ||
| 24 | Description | |
| 25 | ----------- | |
| 26 | ||
| 27 | Returns the result of short-circuit *logical and* (``&&``) operation on its arguments. | |
| 28 | ||
| 29 | ||
| 30 | Header | |
| 31 | ------ | |
| 32 | ||
| 33 | .. parsed-literal:: | |
| 34 | ||
| 35 | #include <boost/mpl/and.hpp> | |
| 36 | #include <boost/mpl/logical.hpp> | |
| 37 | ||
| 38 | ||
| 39 | Parameters | |
| 40 | ---------- | |
| 41 | ||
| 42 | +---------------+---------------------------+-----------------------------------------------+ | |
| 43 | | Parameter | Requirement | Description | | |
| 44 | +===============+===========================+===============================================+ | |
| 45 | | |F1...Fn| | Nullary |Metafunction| | Operation's arguments. | | |
| 46 | +---------------+---------------------------+-----------------------------------------------+ | |
| 47 | ||
| 48 | ||
| 49 | Expression semantics | |
| 50 | -------------------- | |
| 51 | ||
| 52 | For arbitrary nullary |Metafunction|\ s |f1...fn|: | |
| 53 | ||
| 54 | .. parsed-literal:: | |
| 55 | ||
| 56 | typedef and_<f1,f2,\ |...|\ ,f\ *n*\>::type r; | |
| 57 | ||
| 58 | :Return type: | |
| 59 | |Integral Constant|. | |
| 60 | ||
| 61 | :Semantics: | |
| 62 | ``r`` is ``false_`` if either of ``f1::type::value``, ``f2::type::value``,... | |
| 63 | ``fn::type::value`` expressions evaluates to ``false``, and ``true_`` otherwise; | |
| 64 | guarantees left-to-right evaluation; the operands subsequent to the first | |
| 65 | ``f``\ *i* metafunction that evaluates to ``false`` are not evaluated. | |
| 66 | ||
| 67 | ||
| 68 | .. .......................................................................... | |
| 69 | ||
| 70 | .. parsed-literal:: | |
| 71 | ||
| 72 | typedef and_<f1,f2,\ |...|\ ,f\ *n*\> r; | |
| 73 | ||
| 74 | :Return type: | |
| 75 | |Integral Constant|. | |
| 76 | ||
| 77 | :Semantics: | |
| 78 | Equivalent to | |
| 79 | ||
| 80 | .. parsed-literal:: | |
| 81 | ||
| 82 | struct r : and_<f1,f2,\ |...|\ ,f\ *n*\>::type {}; | |
| 83 | ||
| 84 | ||
| 85 | Example | |
| 86 | ------- | |
| 87 | ||
| 88 | .. parsed-literal:: | |
| 89 | ||
| 90 | struct unknown; | |
| 91 | ||
| 92 | BOOST_MPL_ASSERT(( and_< true\_,true\_ > )); | |
| 93 | BOOST_MPL_ASSERT_NOT(( and_< false\_,true\_ > )); | |
| 94 | BOOST_MPL_ASSERT_NOT(( and_< true\_,false\_ > )); | |
| 95 | BOOST_MPL_ASSERT_NOT(( and_< false\_,false\_ > )); | |
| 96 | BOOST_MPL_ASSERT_NOT(( and_< false\_,unknown > )); // OK | |
| 97 | BOOST_MPL_ASSERT_NOT(( and_< false\_,unknown,unknown > )); // OK too | |
| 98 | ||
| 99 | ||
| 100 | See also | |
| 101 | -------- | |
| 102 | ||
| 103 | |Metafunctions|, |Logical Operations|, |or_|, |not_| | |
| 104 | ||
| 105 | ||
| 106 |