uniformly_gettable.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) 2025 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_COLLECTIONS_UNIFORMLY_GETTABLE_HPP
#define OPENKALMAN_COLLECTIONS_UNIFORMLY_GETTABLE_HPP

#include "gettable.hpp"
#include "collections/traits/size_of.hpp"
#include "collections/concepts/sized.hpp"

namespace OpenKalman::collections
{
#if not defined(__cpp_concepts) or __cpp_generic_lambdas < 201707L
  namespace detail
  {
    template<typename T, typename = std::make_index_sequence<size_of<T>::value>>
    struct uniformly_gettable_sized_impl : std::false_type {};

    template<typename T, std::size_t...i>
    struct uniformly_gettable_sized_impl<T, std::index_sequence<i...>> : std::bool_constant<(... and gettable<i, T>)> {};


    template<typename T, typename = void>
    struct uniformly_gettable_sized : std::false_type {};

    template<typename T>
    struct uniformly_gettable_sized<T, std::enable_if_t<size_of<T>::value != stdex::dynamic_extent>>
      : uniformly_gettable_sized_impl<T> {};

  }
#endif


  template<typename T>
#if defined(__cpp_concepts) and __cpp_generic_lambdas >= 201707L
  concept uniformly_gettable =
    sized<T> and
    (size_of_v<T> != stdex::dynamic_extent) and
    []<std::size_t...i>(std::index_sequence<i...>) { return (... and gettable<i, T>); } (std::make_index_sequence<size_of_v<T>>{});
#else
  inline constexpr bool uniformly_gettable =
    sized<T> and
    detail::uniformly_gettable_sized<T>::value;
#endif


}

#endif