hermitian_matrix.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_HERMITIAN_MATRIX_HPP
#define OPENKALMAN_HERMITIAN_MATRIX_HPP


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

    template<typename T>
    struct is_inferred_hermitian_matrix<T, std::enable_if_t<not values::complex<typename scalar_type_of<T>::type> or
      values::not_complex<constant_coefficient<T>> or values::not_complex<constant_diagonal_coefficient<T>>>>
      : std::true_type {};
  };
#endif


  template<typename T, Applicability b = Applicability::guaranteed>
#ifdef __cpp_concepts
  concept hermitian_matrix = indexible<T> and square_shaped<T, b> and
    (interface::indexible_object_traits<std::decay_t<T>>::is_hermitian or
      ((constant_matrix<T> or diagonal_matrix<T>) and
      (not values::complex<scalar_type_of_t<T>> or
        values::not_complex<constant_coefficient<T>> or values::not_complex<constant_diagonal_coefficient<T>>)));
#else
  constexpr bool hermitian_matrix = square_shaped<T, b> and
    (interface::is_explicitly_hermitian<T>::value or
      ((constant_matrix<T> or diagonal_matrix<T>) and detail::is_inferred_hermitian_matrix<T>::value));
#endif


} // namespace OpenKalman

#endif //OPENKALMAN_HERMITIAN_MATRIX_HPP