callable_traits/detail/forward_declarations.hpp

0001 #ifndef BOOST_CLBL_TRTS_DETAIL_FORWARD_DECLARATIONS
0002 #define BOOST_CLBL_TRTS_DETAIL_FORWARD_DECLARATIONS
0003 #include <boost/callable_traits/detail/config.hpp>
0004 #include <boost/callable_traits/detail/default_callable_traits.hpp>
0005
0006 namespace boost { namespace callable_traits { namespace detail {
0007
0008 template<typename T>
0009 struct function;
0010
0011 template<typename T>
0012 struct has_normal_call_operator
0013 {
0014     template<typename N, N Value>
0015     struct check { check(std::nullptr_t) {} };
0016
0017     template<typename U>
0018     static std::int8_t test(
0019         check<decltype(&U::operator()), &U::operator()>);
0020
0021     template<typename>
0022     static std::int16_t test(...);
0023
0024     static constexpr bool value =
0025         sizeof(test<T>(nullptr)) == sizeof(std::int8_t);
0026 };
0027
0028 struct callable_dummy {
0029     void operator()() {}
0030 };
0031
0032 template<typename T>
0033 using default_to_function_object = typename std::conditional<
0034     has_normal_call_operator<T>::value,
0035     T, callable_dummy>::type;
0036
0037 template<typename T>
0038 struct pmf;
0039
0040 template<typename T>
0041 struct pmd;
0042
0043 template<typename F, typename T = typename std::remove_reference<F>::type>
0044 using function_object_base = typename std::conditional<
0045     has_normal_call_operator<T>::value,
0046     pmf<decltype(&default_to_function_object<T>::operator())>,
0047     default_callable_traits<T>>::type;
0048
0049 template<typename T, typename Base = function_object_base<T>>
0050 struct function_object;
0051
0052 }}} // namespace boost::callable_traits::detail
0053
0054 #endif // #ifndef BOOST_CLBL_TRTS_DETAIL_FORWARD_DECLARATIONS