Ref.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_EIGEN_TRAITS_REF_HPP
#define OPENKALMAN_EIGEN_TRAITS_REF_HPP

#include <type_traits>


namespace OpenKalman::interface
{
  template<typename PlainObjectType, int Options, typename StrideType>
  struct object_traits<Eigen::Ref<PlainObjectType, Options, StrideType>>
    : Eigen3::object_traits_base<Eigen::Ref<PlainObjectType, Options, StrideType>>
  {
    template<typename Arg>
    static constexpr auto get_constant(const Arg& arg)
    {
      if constexpr (values::fixed<constant_value<PlainObjectType>>)
        return constant_value<PlainObjectType> {};
      else
        return std::monostate {};
    }

    template<typename Arg>
    static constexpr auto get_constant_diagonal(const Arg& arg)
    {
      if constexpr (values::fixed<constant_diagonal_value<PlainObjectType>>)
        return constant_diagonal_value<PlainObjectType> {};
      else
        return std::monostate {};
    }


    static constexpr data_layout layout = std::is_same_v<StrideType, Eigen::Stride<0, 0>> ? layout_of_v<PlainObjectType> : data_layout::stride;

  };


}

#endif