layout_of.hpp

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/* This file is part of OpenKalman, a header-only C++ library for
 * Kalman filters and other recursive filters.
 *
 * Copyright (c) 2019-2023 Christopher Lee Ogden <ogden@gatech.edu>
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at https://mozilla.org/MPL/2.0/.
 */

#ifndef OPENKALMAN_LAYOUT_OF_HPP
#define OPENKALMAN_LAYOUT_OF_HPP


namespace OpenKalman
{
#ifndef __cpp_lib_concepts
  namespace detail
  {
    template<typename T, typename = void>
    struct has_layout : std::false_type {};

    template<typename T>
      struct has_layout<T, std::void_t<decltype(interface::indexible_object_traits<T>::layout)>> : std::true_type {};
  } // namespace detail
#endif


#ifdef __cpp_concepts
  template<typename T>
#else
  template<typename T, typename = void>
#endif
  struct layout_of : std::integral_constant<Layout, Layout::none> {};


#ifdef __cpp_concepts
  template<typename T> requires requires { interface::indexible_object_traits<std::decay_t<T>>::layout; }
  struct layout_of<T>
#else
  template<typename T>
  struct layout_of<T, std::enable_if_t<detail::has_layout<std::decay_t<T>>::value>>
#endif
    : std::integral_constant<Layout, interface::indexible_object_traits<std::decay_t<T>>::layout> {};


  template<typename T>
  static constexpr auto layout_of_v = layout_of<T>::value;


} // namespace OpenKalman

#endif //OPENKALMAN_LAYOUT_OF_HPP