variant_types.hpp

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//
// Copyright (C) 2014, 2015 Ableton AG, Berlin. All rights reserved.
//
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// copy of this software and associated documentation files (the "Software"),
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// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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#pragma once

#include <atria/estd/type_traits.hpp>
#include <atria/meta/copy_traits.hpp>
#include <atria/meta/pack.hpp>

#include <ableton/build_system/Warnings.hpp>
ABL_DISABLE_WARNINGS
#include <boost/mpl/transform.hpp>
ABL_RESTORE_WARNINGS

namespace atria {
namespace variant {

namespace detail {

template <typename T, typename Enable=void>
struct variant_types_aux {};

template <typename T>
struct variant_types_aux<T, estd::void_t<typename T::variant_types> >
{
  using type = typename T::variant_types;
};

} // namespace detail

template <typename T>
struct variant_types_impl
  : detail::variant_types_aux<T>
{};

template <typename... Ts>
struct variant_types_impl<meta::pack<Ts...> >
{
  using type = meta::pack<Ts...>;
};

template <typename T>
struct variant_types
  : boost::mpl::transform<
     typename variant_types_impl<estd::decay_t<T> >::type,
     meta::copy_decay<T, boost::mpl::_1 > >
{};
ABL_METAFUNCTION_T(variant_types);

} // namespace variant
} // namespace atria