scalar_type_of_deprecated.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_DESCRIPTORS_SCALAR_TYPE_OF_HPP
#define OPENKALMAN_DESCRIPTORS_SCALAR_TYPE_OF_HPP

#include <type_traits>
#include "linear-algebra/coordinates/interfaces/coordinate_descriptor_traits.hpp"
#include "linear-algebra/coordinates/concepts/descriptor.hpp"
#include "linear-algebra/coordinates/concepts/descriptor_range.hpp"
#include "linear-algebra/coordinates/concepts/pattern.hpp"

namespace OpenKalman::coordinates
{
#ifdef __cpp_concepts
  template<pattern T>
#else
  template<typename T, typename = void, typename = void>
#endif
  struct scalar_type_of { using type = double; };


  template<typename T>
  using scalar_type_of_t = typename scalar_type_of<T>::type;


#ifdef __cpp_concepts
  template<descriptor T> requires
    requires { typename interface::coordinate_descriptor_traits<std::decay_t<T>>::scalar_type; }
  struct scalar_type_of<T>
#else
  template<typename T>
  struct scalar_type_of<T, std::enable_if_t<descriptor<T>>,
    std::void_t<typename interface::coordinate_descriptor_traits<std::decay_t<T>>::scalar_type>>
#endif
  {
    using type = typename interface::coordinate_descriptor_traits<std::decay_t<T>>::scalar_type;
  };


#ifdef __cpp_concepts
  template<descriptor_range T> requires
    requires { typename interface::coordinate_set_traits<std::decay_t<T>>::scalar_type; }
  struct scalar_type_of<T>
#else
  template<typename T>
  struct scalar_type_of<T, std::enable_if_t<descriptor_range<T>>,
    std::void_t<typename interface::coordinate_set_traits<std::decay_t<T>>::scalar_type>>
#endif
  {
    using type = typename interface::coordinate_set_traits<std::decay_t<T>>::scalar_type;
  };


#ifdef __cpp_concepts
  template<descriptor_tuple T> requires (not descriptor_range<T>) and
    requires { typename interface::coordinate_set_traits<std::decay_t<T>>::scalar_type; }
  struct scalar_type_of<T>
#else
  template<typename T>
  struct scalar_type_of<T, std::enable_if_t<descriptor_tuple<T>>,
    std::void_t<typename interface::coordinate_set_traits<std::decay_t<T>>::scalar_type>>
#endif
  {
    using type = typename interface::coordinate_set_traits<std::decay_t<T>>::scalar_type;
  };


} // namespace OpenKalman::coordinates

#endif //OPENKALMAN_DESCRIPTORS_SCALAR_TYPE_OF_HPP