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