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