action_list_implementation.hpp

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// This file is part of the Acts project.
//
// Copyright (C) 2018 CERN for the benefit of the Acts project
//
// 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 http://mozilla.org/MPL/2.0/.

#pragma once
#include "Acts/Utilities/detail/MPL/type_collector.hpp"

namespace Acts {

namespace detail {

namespace {

template <bool has_result = true>
struct action_caller {
  template <typename actor, typename result_t, typename propagator_state_t,
            typename stepper_t>
  static void action(const actor& act, propagator_state_t& state,
                     const stepper_t& stepper, result_t& result) {
    act(state, stepper, result.template get<detail::result_type_t<actor>>());
  }
};

template <>
struct action_caller<false> {
  template <typename actor, typename result_t, typename propagator_state_t,
            typename stepper_t>
  static void action(const actor& act, propagator_state_t& state,
                     const stepper_t& stepper, result_t& /*unused*/) {
    act(state, stepper);
  }
};
}  // end of anonymous namespace

template <typename... actors>
struct action_list_impl;

template <typename first, typename... others>
struct action_list_impl<first, others...> {
  template <typename T, typename result_t, typename propagator_state_t,
            typename stepper_t>
  static void action(const T& obs_tuple, propagator_state_t& state,
                     const stepper_t& stepper, result_t& result) {
    constexpr bool has_result = has_result_type_v<first>;
    const auto& this_action = std::get<first>(obs_tuple);
    action_caller<has_result>::action(this_action, state, stepper, result);
    action_list_impl<others...>::action(obs_tuple, state, stepper, result);
  }
};

template <typename last>
struct action_list_impl<last> {
  template <typename T, typename result_t, typename propagator_state_t,
            typename stepper_t>
  static void action(const T& obs_tuple, propagator_state_t& state,
                     const stepper_t& stepper, result_t& result) {
    constexpr bool has_result = has_result_type_v<last>;
    const auto& this_action = std::get<last>(obs_tuple);
    action_caller<has_result>::action(this_action, state, stepper, result);
  }
};

template <>
struct action_list_impl<> {
  template <typename T, typename result_t, typename propagator_state_t,
            typename stepper_t>
  static void action(const T& /*unused*/, propagator_state_t& /*unused*/,
                     const stepper_t& /*unused*/, result_t& /*unused*/) {}
};

}  // namespace detail
}  // namespace Acts