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{ namespace multiprecision{ namespace detail{
15 
16 template <int N>
17 struct dummy_size{};
18 
19 template<typename S, typename T>
20 struct has_generic_interconversion
21 {
22    typedef typename mpl::if_c<
23       is_number<S>::value && is_number<T>::value,
24       typename mpl::if_c<
25          number_category<S>::value == number_kind_integer,
26          typename mpl::if_c<
27             number_category<T>::value == number_kind_integer
28             || number_category<T>::value == number_kind_floating_point
29             || number_category<T>::value == number_kind_rational
30             || number_category<T>::value == number_kind_fixed_point,
31             mpl::true_,
32             mpl::false_
33          >::type,
34          typename mpl::if_c<
35             number_category<S>::value == number_kind_rational,
36             typename mpl::if_c<
37                number_category<T>::value == number_kind_rational
38                || number_category<T>::value == number_kind_rational,
39                mpl::true_,
40                mpl::false_
41             >::type,
42             typename mpl::if_c<
43                number_category<T>::value == number_kind_floating_point,
44                mpl::true_,
45                mpl::false_
46             >::type
47          >::type
48       >::type,
49       mpl::false_
50    >::type type;
51 };
52 
53 template<typename S, typename T>
54 struct is_explicitly_convertible_imp
55 {
56 #ifndef BOOST_NO_SFINAE_EXPR
57    template<typename S1, typename T1>
58    static type_traits::yes_type selector(dummy_size<sizeof(static_cast<T1>(declval<S1>()))>*);
59 
60    template<typename S1, typename T1>
61    static type_traits::no_type selector(...);
62 
63    static const bool value = sizeof(selector<S,T>(0)) == sizeof(type_traits::yes_type);
64 
65    typedef boost::integral_constant<bool,value> type;
66 #else
67    typedef typename has_generic_interconversion<S, T>::type gen_type;
68    typedef mpl::bool_<boost::is_convertible<S, T>::value || gen_type::value> type;
69 #endif
70 };
71 
72 template<typename From, typename To>
73 struct is_explicitly_convertible : public is_explicitly_convertible_imp<From, To>::type
74 {
75 };
76 
77 }}} // namespaces
78 
79 #endif
80 
81