| 1 | // Boost.TypeErasure library |
|---|
| 2 | // |
|---|
| 3 | // Copyright 2011 Steven Watanabe |
|---|
| 4 | // |
|---|
| 5 | // Distributed under the Boost Software License Version 1.0. (See |
|---|
| 6 | // accompanying file LICENSE_1_0.txt or copy at |
|---|
| 7 | // http://www.boost.org/LICENSE_1_0.txt) |
|---|
| 8 | // |
|---|
| 9 | // $Id$ |
|---|
| 10 | |
|---|
| 11 | #ifndef BOOST_TYPE_ERASURE_RELAXED_HPP_INCLUDED |
|---|
| 12 | #define BOOST_TYPE_ERASURE_RELAXED_HPP_INCLUDED |
|---|
| 13 | |
|---|
| 14 | #include <boost/mpl/vector.hpp> |
|---|
| 15 | #include <boost/mpl/bool.hpp> |
|---|
| 16 | #include <boost/mpl/is_sequence.hpp> |
|---|
| 17 | #include <boost/mpl/find_if.hpp> |
|---|
| 18 | #include <boost/mpl/not.hpp> |
|---|
| 19 | #include <boost/mpl/end.hpp> |
|---|
| 20 | #include <boost/type_traits/is_same.hpp> |
|---|
| 21 | |
|---|
| 22 | namespace boost { |
|---|
| 23 | namespace type_erasure { |
|---|
| 24 | |
|---|
| 25 | template<class T> |
|---|
| 26 | struct is_relaxed; |
|---|
| 27 | |
|---|
| 28 | namespace detail { |
|---|
| 29 | |
|---|
| 30 | template<class T> |
|---|
| 31 | struct is_relaxed_impl : |
|---|
| 32 | ::boost::mpl::not_< |
|---|
| 33 | typename ::boost::is_same< |
|---|
| 34 | typename ::boost::mpl::find_if< |
|---|
| 35 | T, |
|---|
| 36 | ::boost::type_erasure::is_relaxed< ::boost::mpl::_1> |
|---|
| 37 | >::type, |
|---|
| 38 | typename ::boost::mpl::end<T>::type |
|---|
| 39 | >::type |
|---|
| 40 | >::type |
|---|
| 41 | {}; |
|---|
| 42 | |
|---|
| 43 | } |
|---|
| 44 | |
|---|
| 45 | /** |
|---|
| 46 | * This special concept enables various useful default behavior that |
|---|
| 47 | * makes @ref any act like an ordinary object. By default @ref any |
|---|
| 48 | * forwards all operations to the underlying type, and provides only |
|---|
| 49 | * the operations that are specified in its @c Concept. |
|---|
| 50 | * |
|---|
| 51 | * In detail, @ref relaxed enables the following: |
|---|
| 52 | * - A raw value can be assigned to an @ref any. This will replace |
|---|
| 53 | * the value stored by the @ref any. (But note that if @ref assignable |
|---|
| 54 | * is present, it takes priority.) |
|---|
| 55 | * - assignment of @ref any uses the constructor if it can't |
|---|
| 56 | * use @ref assignable (either because @ref assignable is missing, |
|---|
| 57 | * or because the stored types do not match). |
|---|
| 58 | * - default construction of @ref any is allowed and creates a null any. |
|---|
| 59 | * - @ref equality_comparable "equality_comparable": If the types do not |
|---|
| 60 | * match, it will return false. |
|---|
| 61 | * - @ref less_than_comparable "less_than_comparable": If the types do not |
|---|
| 62 | * match, the ordering will be according to |
|---|
| 63 | * @c std::type_info::before. |
|---|
| 64 | * - if the arguments to any other function do not match, it will throw |
|---|
| 65 | * a @ref bad_function_call exception instead of having undefined |
|---|
| 66 | * behavior. |
|---|
| 67 | */ |
|---|
| 68 | struct relaxed : ::boost::mpl::vector0<> {}; |
|---|
| 69 | |
|---|
| 70 | /** |
|---|
| 71 | * A metafunction indicating whether @c Concept |
|---|
| 72 | * includes @ref relaxed. |
|---|
| 73 | */ |
|---|
| 74 | template<class Concept> |
|---|
| 75 | struct is_relaxed : |
|---|
| 76 | ::boost::mpl::eval_if< ::boost::mpl::is_sequence<Concept>, |
|---|
| 77 | ::boost::type_erasure::detail::is_relaxed_impl<Concept>, |
|---|
| 78 | ::boost::mpl::false_ |
|---|
| 79 | >::type |
|---|
| 80 | {}; |
|---|
| 81 | |
|---|
| 82 | /** INTERNAL ONLY */ |
|---|
| 83 | template<> |
|---|
| 84 | struct is_relaxed< ::boost::type_erasure::relaxed> : |
|---|
| 85 | ::boost::mpl::true_ |
|---|
| 86 | {}; |
|---|
| 87 | |
|---|
| 88 | } |
|---|
| 89 | } |
|---|
| 90 | |
|---|
| 91 | #endif |
|---|
| 92 | |
|---|
