boost/variant/detail/make_variant_list.hpp
//-----------------------------------------------------------------------------
// boost variant/detail/make_variant_list.hpp header file
// See http://www.boost.org for updates, documentation, and revision history.
//-----------------------------------------------------------------------------
//
// Copyright (c) 2002-2003 Eric Friedman, Itay Maman
// Copyright (c) 2013-2021 Antony Polukhin
//
// 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_VARIANT_DETAIL_MAKE_VARIANT_LIST_HPP
#define BOOST_VARIANT_DETAIL_MAKE_VARIANT_LIST_HPP
#include <boost/variant/variant_fwd.hpp>
#include <boost/mpl/list.hpp>
#include <boost/preprocessor/cat.hpp>
#include <boost/preprocessor/enum.hpp>
namespace boost {
namespace detail { namespace variant {
///////////////////////////////////////////////////////////////////////////////
// (detail) metafunction make_variant_list
//
// Provides a MPL-compatible sequence with the specified non-void types
// as arguments.
//
// Rationale: see class template convert_void (variant_fwd.hpp) and using-
// declaration workaround (below).
//
#if !defined(BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES)
template < typename... T >
struct make_variant_list
{
typedef typename mpl::list< T... >::type type;
};
#else // defined(BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES)
template < BOOST_VARIANT_ENUM_PARAMS(typename T) >
struct make_variant_list
{
public: // metafunction result
// [Define a macro to convert any void(NN) tags to mpl::void...]
# define BOOST_VARIANT_AUX_CONVERT_VOID(z, N,_) \
typename convert_void< BOOST_PP_CAT(T,N) >::type
// [...so that the specified types can be passed to mpl::list...]
typedef typename mpl::list<
BOOST_PP_ENUM(
BOOST_VARIANT_LIMIT_TYPES
, BOOST_VARIANT_AUX_CONVERT_VOID
, _
)
>::type type;
// [...and, finally, the conversion macro can be undefined:]
# undef BOOST_VARIANT_AUX_CONVERT_VOID
};
#endif // BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES workaround
}} // namespace detail::variant
} // namespace boost
#endif // BOOST_VARIANT_DETAIL_MAKE_VARIANT_LIST_HPP