index_count.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_INDEX_COUNT_HPP
#define OPENKALMAN_INDEX_COUNT_HPP


namespace OpenKalman
{
#ifdef __cpp_concepts
  template<typename T>
#else
  template<typename T, typename = void>
#endif
  struct index_count;


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

    template<typename T>
    struct static_count_indices_defined<T, std::enable_if_t<interface::count_indices_defined_for<T>>>
    : std::bool_constant<values::fixed<decltype(count_indices(std::declval<T>()))>> {};
  }
#endif


#ifdef __cpp_concepts
  template<typename T> requires requires(T t) { {count_indices(t)} -> values::fixed; }
  struct index_count<T>
#else
  template<typename T>
  struct index_count<T, std::enable_if_t<detail::static_count_indices_defined<T>::value>>
#endif
    : std::integral_constant<std::size_t, std::decay_t<decltype(count_indices(std::declval<T>()))>::value> {};


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

    template<typename T>
    struct dynamic_count_indices_defined<T, std::enable_if_t<interface::count_indices_defined_for<T>>>
    : std::bool_constant<values::index<decltype(count_indices(std::declval<T>()))> and
        values::dynamic<decltype(count_indices(std::declval<T>()))>> {};
  }
#endif


#ifdef __cpp_concepts
  template<typename T> requires requires(T t) { {count_indices(t)} -> values::dynamic; }
  struct index_count<T>
#else
  template<typename T>
  struct index_count<T, std::enable_if_t<detail::dynamic_count_indices_defined<T>::value>>
#endif
    : std::integral_constant<std::size_t, dynamic_size> {};


  template<typename T>
  static constexpr std::size_t index_count_v = index_count<T>::value;


} // namespace OpenKalman

#endif //OPENKALMAN_INDEX_COUNT_HPP