1 /////////////////////////////////////////////////////////////////////////////// 2 // Copyright Vicente J. Botet Escriba 2009-2011 3 // Copyright 2012 John Maddock. Distributed under the Boost 4 // Software License, Version 1.0. (See accompanying file 5 // LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) 6 7 #ifndef BOOST_MP_EXPLICIT_CONVERTIBLE_HPP 8 #define BOOST_MP_EXPLICIT_CONVERTIBLE_HPP 9 10 #include <boost/type_traits/is_convertible.hpp> 11 #include <boost/utility/declval.hpp> 12 13 14 namespace boost { 15 namespace multiprecision { 16 namespace detail { 17 18 template <int N> 19 struct dummy_size {}; 20 21 template<typename S, typename T> 22 struct has_generic_interconversion 23 { 24 typedef typename mpl::if_c < 25 is_number<S>::value && is_number<T>::value, 26 typename mpl::if_c < 27 number_category<S>::value == number_kind_integer, 28 typename mpl::if_c< 29 number_category<T>::value == number_kind_integer 30 || number_category<T>::value == number_kind_floating_point 31 || number_category<T>::value == number_kind_rational 32 || number_category<T>::value == number_kind_fixed_point, 33 mpl::true_, 34 mpl::false_ 35 >::type, 36 typename mpl::if_c< 37 number_category<S>::value == number_kind_rational, 38 typename mpl::if_c< 39 number_category<T>::value == number_kind_rational 40 || number_category<T>::value == number_kind_rational, 41 mpl::true_, 42 mpl::false_ 43 >::type, 44 typename mpl::if_c< 45 number_category<T>::value == number_kind_floating_point, 46 mpl::true_, 47 mpl::false_ 48 >::type 49 >::type 50 > ::type, 51 mpl::false_ 52 > ::type type; 53 }; 54 55 template<typename S, typename T> 56 struct is_explicitly_convertible_imp 57 { 58 #ifndef BOOST_NO_SFINAE_EXPR 59 template<typename S1, typename T1> 60 static type_traits::yes_type selector(dummy_size<sizeof(static_cast<T1>(declval<S1>()))>*); 61 62 template<typename S1, typename T1> 63 static type_traits::no_type selector(...); 64 65 static const bool value = sizeof(selector<S, T>(0)) == sizeof(type_traits::yes_type); 66 67 typedef boost::integral_constant<bool, value> type; 68 #else 69 typedef typename has_generic_interconversion<S, T>::type gen_type; 70 typedef mpl::bool_<boost::is_convertible<S, T>::value || gen_type::value> type; 71 #endif 72 }; 73 74 template<typename From, typename To> 75 struct is_explicitly_convertible : public is_explicitly_convertible_imp<From, To>::type 76 { 77 }; 78 79 #ifdef BOOST_NO_SFINAE_EXPR 80 template<class Backend1, expression_template_option ExpressionTemplates1, class Backend2, expression_template_option ExpressionTemplates2> 81 struct is_explicitly_convertible<number<Backend1, ExpressionTemplates1>, number<Backend2, ExpressionTemplates2> > 82 : public is_explicitly_convertible<Backend1, Backend2> 83 { 84 }; 85 #endif 86 87 }}} // namespaces 88 89 #endif 90 91