get_chip.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) 2022-2023 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_GET_CHIP_HPP
#define OPENKALMAN_GET_CHIP_HPP

namespace OpenKalman
{
#ifdef __cpp_concepts
  template<std::size_t...indices, indexible Arg, values::index...Ixs> requires (sizeof...(indices) == sizeof...(Ixs))
#else
  template<std::size_t...indices, typename Arg, typename...Ixs, std::enable_if_t<
    indexible<Arg> and (values::index<Ixs> and ...) and (sizeof...(indices) == sizeof...(Ixs)), int> = 0>
#endif
  constexpr decltype(auto)
  get_chip(Arg&& arg, Ixs...ixs)
  {
    (... , []{
      if constexpr (values::fixed<Ixs> and not dynamic_dimension<Arg, indices>)
        static_assert(std::decay_t<Ixs>::value < index_dimension_of_v<Arg, indices>, "get_chip: indices must be in range");
    }());

    if constexpr (sizeof...(indices) == 0) return std::forward<Arg>(arg);
    else return get_slice<indices...>(
      std::forward<Arg>(arg),
      std::tuple{ixs...}, // begin points
      std::tuple{(std::integral_constant<decltype(indices), 1> {})...}); // block sizes (always 1 in each collapsed dimension)
  }


} // namespace OpenKalman

#endif //OPENKALMAN_GET_CHIP_HPP