dynamic_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) 2023-2024 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_DYNAMIC_INDEX_COUNT_HPP
#define OPENKALMAN_DYNAMIC_INDEX_COUNT_HPP

#include "linear-algebra/traits/index_count.hpp"
#include "linear-algebra/traits/index_dimension_of.hpp"

namespace OpenKalman
{
  namespace detail
  {
    template<typename T, std::size_t...I>
    constexpr std::size_t dynamic_index_count_impl(std::index_sequence<I...>)
    {
      return ((index_dimension_of_v<T, I> == stdex::dynamic_extent ? 1 : 0) + ... + 0);
    }
  }


#ifdef __cpp_concepts
  template<typename T>
#else
  template<typename T, typename = void>
#endif
  struct dynamic_index_count  {};


#ifdef __cpp_concepts
  template<indexible T>
  struct dynamic_index_count<T>
#else
  template<typename T>
  struct dynamic_index_count<T, std::enable_if_t<indexible<T>>>
#endif
    : std::integral_constant<std::size_t, detail::dynamic_index_count_impl<T>(std::make_index_sequence<index_count_v<T>> {})> {};


#ifdef __cpp_concepts
  template<indexible T>
#else
  template<typename T>
#endif
  static constexpr std::size_t dynamic_index_count_v = dynamic_index_count<T>::value;


}

#endif