Boost C++ Libraries

boost/multiprecision/traits/explicit_conversion.hpp

///////////////////////////////////////////////////////////////////////////////
//  Copyright Vicente J. Botet Escriba 2009-2011
//  Copyright 2012 John Maddock. Distributed under the Boost
//  Software License, Version 1.0. (See accompanying file
//  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

#ifndef BOOST_MP_EXPLICIT_CONVERTIBLE_HPP
#define BOOST_MP_EXPLICIT_CONVERTIBLE_HPP

#include <boost/config.hpp>
#include <boost/type_traits/conditional.hpp>
#include <boost/type_traits/integral_constant.hpp>
#include <boost/type_traits/is_convertible.hpp>
#include <boost/type_traits/declval.hpp>
#include <boost/multiprecision/detail/number_base.hpp> // number_category

namespace boost {
namespace multiprecision {
namespace detail {

template <unsigned int N>
struct dummy_size
{};

template <typename S, typename T>
struct has_generic_interconversion
{
   typedef typename boost::conditional<
       is_number<S>::value && is_number<T>::value,
       typename boost::conditional<
           number_category<S>::value == number_kind_integer,
           typename boost::conditional<
               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,
               boost::true_type,
               boost::false_type>::type,
           typename boost::conditional<
               number_category<S>::value == number_kind_rational,
               typename boost::conditional<
                   number_category<T>::value == number_kind_rational || number_category<T>::value == number_kind_rational,
                   boost::true_type,
                   boost::false_type>::type,
               typename boost::conditional<
                   number_category<T>::value == number_kind_floating_point,
                   boost::true_type,
                   boost::false_type>::type>::type>::type,
       boost::false_type>::type type;
};

template <typename S, typename T>
struct is_explicitly_convertible_imp
{
#ifndef BOOST_NO_SFINAE_EXPR
   template <typename S1, typename T1>
   static type_traits::yes_type selector(dummy_size<sizeof(new T1(boost::declval<
#if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
                                                                  S1
#else
                                                                  S1 const&
#endif
                                                                  >()))>*);

   template <typename S1, typename T1>
   static type_traits::no_type selector(...);

   static const bool value = sizeof(selector<S, T>(0)) == sizeof(type_traits::yes_type);

   typedef boost::integral_constant<bool, value> type;
#else
   typedef typename has_generic_interconversion<S, T>::type                                      gen_type;
   typedef boost::integral_constant<bool, boost::is_convertible<S, T>::value || gen_type::value> type;
#endif
};

template <typename From, typename To>
struct is_explicitly_convertible : public is_explicitly_convertible_imp<From, To>::type
{
};

#ifdef BOOST_NO_SFINAE_EXPR
template <class Backend1, expression_template_option ExpressionTemplates1, class Backend2, expression_template_option ExpressionTemplates2>
struct is_explicitly_convertible<number<Backend1, ExpressionTemplates1>, number<Backend2, ExpressionTemplates2> >
    : public is_explicitly_convertible<Backend1, Backend2>
{
};
#endif

}}} // namespace boost::multiprecision::detail

#endif