boost/multiprecision/traits/explicit_conversion.hpp

   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/config.hpp>
  11 #include <boost/type_traits/conditional.hpp>
  12 #include <boost/type_traits/integral_constant.hpp>
  13 #include <boost/type_traits/is_convertible.hpp>
  14 #include <boost/type_traits/declval.hpp>
  15 #include <boost/multiprecision/detail/number_base.hpp> // number_category
  16
  17 namespace boost {
  18 namespace multiprecision {
  19 namespace detail {
  20
  21 template <unsigned int N>
  22 struct dummy_size
  23 {};
  24
  25 template <typename S, typename T>
  26 struct has_generic_interconversion
  27 {
  28    typedef typename boost::conditional<
  29        is_number<S>::value && is_number<T>::value,
  30        typename boost::conditional<
  31            number_category<S>::value == number_kind_integer,
  32            typename boost::conditional<
  33                number_category<T>::value == number_kind_integer || number_category<T>::value == number_kind_floating_point || number_category<T>::value == number_kind_rational || number_category<T>::value == number_kind_fixed_point,
  34                boost::true_type,
  35                boost::false_type>::type,
  36            typename boost::conditional<
  37                number_category<S>::value == number_kind_rational,
  38                typename boost::conditional<
  39                    number_category<T>::value == number_kind_rational || number_category<T>::value == number_kind_rational,
  40                    boost::true_type,
  41                    boost::false_type>::type,
  42                typename boost::conditional<
  43                    number_category<T>::value == number_kind_floating_point,
  44                    boost::true_type,
  45                    boost::false_type>::type>::type>::type,
  46        boost::false_type>::type type;
  47 };
  48
  49 template <typename S, typename T>
  50 struct is_explicitly_convertible_imp
  51 {
  52 #ifndef BOOST_NO_SFINAE_EXPR
  53    template <typename S1, typename T1>
  54    static type_traits::yes_type selector(dummy_size<sizeof(new T1(boost::declval<
  55 #if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
  56                                                                   S1
  57 #else
  58                                                                   S1 const&
  59 #endif
  60                                                                   >()))>*);
  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 boost::integral_constant<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 }}} // namespace boost::multiprecision::detail
  88
  89 #endif