boost/boost/core/underlying_type.hpp

//  underlying_type.hpp  ---------------------------------------------------------//

//  Copyright Beman Dawes, 2009
//  Copyright (C) 2011-2012 Vicente J. Botet Escriba
//  Copyright (C) 2012 Anthony Williams
//  Copyright (C) 2014 Andrey Semashev

//  Distributed under the Boost Software License, Version 1.0.
//  See http://www.boost.org/LICENSE_1_0.txt

#ifndef BOOST_CORE_UNDERLYING_TYPE_HPP
#define BOOST_CORE_UNDERLYING_TYPE_HPP

#include <boost/config.hpp>

// GCC 4.7 and later seem to provide std::underlying_type
#if !defined(BOOST_NO_CXX11_HDR_TYPE_TRAITS) || (defined(BOOST_GCC) && BOOST_GCC >= 40700 && defined(__GXX_EXPERIMENTAL_CXX0X__))
#include <type_traits>
#define BOOST_DETAIL_HAS_STD_UNDERLYING_TYPE
#endif

#ifdef BOOST_HAS_PRAGMA_ONCE
#pragma once
#endif

namespace boost {

namespace detail {

template< typename EnumType, typename Void = void >
struct underlying_type_impl;

#if defined(BOOST_NO_CXX11_SCOPED_ENUMS)

// Support for boost/core/scoped_enum.hpp
template< typename EnumType >
struct underlying_type_impl< EnumType, typename EnumType::is_boost_scoped_enum_tag >
{
    /**
     * The member typedef type names the underlying type of EnumType. It is EnumType::underlying_type when the EnumType is an emulated scoped enum,
     */
    typedef typename EnumType::underlying_type type;
};

#endif

#if defined(BOOST_DETAIL_HAS_STD_UNDERLYING_TYPE)

template< typename EnumType, typename Void >
struct underlying_type_impl
{
    typedef typename std::underlying_type< EnumType >::type type;
};

#endif

} // namespace detail

#if !defined(BOOST_NO_CXX11_SCOPED_ENUMS) && !defined(BOOST_DETAIL_HAS_STD_UNDERLYING_TYPE)
#define BOOST_NO_UNDERLYING_TYPE
#endif

/**
 * Meta-function to get the underlying type of a scoped enum.
 *
 * Requires EnumType must be an enum type or the emulation of a scoped enum.
 * If BOOST_NO_UNDERLYING_TYPE is defined, the implementation will not be able
 * to deduce the underlying type of enums. The user is expected to specialize
 * this trait in this case.
 */
template< typename EnumType >
struct underlying_type :
    public detail::underlying_type_impl< EnumType >
{
};

} // namespace boost

#endif  // BOOST_CORE_UNDERLYING_TYPE_HPP