ProcessSequence.h

/*
 * (c) Copyright 2018 CORSIKA Project, corsika-project@lists.kit.edu
 *
 * See file AUTHORS for a list of contributors.
 *
 * This software is distributed under the terms of the GNU General Public
 * Licence version 3 (GPL Version 3). See file LICENSE for a full version of
 * the license.
 */

#ifndef _include_ProcessSequence_h_
#define _include_ProcessSequence_h_

#include <corsika/process/BaseProcess.h>
#include <corsika/process/BoundaryCrossingProcess.h>
#include <corsika/process/ContinuousProcess.h>
#include <corsika/process/DecayProcess.h>
#include <corsika/process/InteractionProcess.h>
#include <corsika/process/ProcessReturn.h>
#include <corsika/process/SecondariesProcess.h>
#include <corsika/process/StackProcess.h>
#include <corsika/units/PhysicalUnits.h>

#include <cmath>
#include <limits>
#include <type_traits>

namespace corsika::process {

  /**
     \class ProcessSequence

     A compile time static list of processes. The compiler will
     generate a new type based on template logic containing all the
     elements.

     \comment Using CRTP pattern,
     https://en.wikipedia.org/wiki/Curiously_recurring_template_pattern
   */

  // define a marker (trait class) to tag any class that qualifies as "Process" for the
  // "ProcessSequence"
  std::false_type is_process_impl(...);
  template <class T>
  using is_process = decltype(is_process_impl(std::declval<T*>()));

  // this is a marker to track which BaseProcess is also a ProcessSequence
  template <typename T>
  struct is_process_sequence : std::false_type {};

  template <typename T>
  bool constexpr is_process_sequence_v = is_process_sequence<T>::value;

  namespace switch_process {
    template <typename A, typename B>
    class SwitchProcess; // fwd-decl.
  }

  // to detect SwitchProcesses inside the ProcessSequence
  template <typename T>
  struct is_switch_process : std::false_type {};

  template <typename T>
  bool constexpr is_switch_process_v = is_switch_process<T>::value;

  template <typename A, typename B>
  struct is_process_sequence<switch_process::SwitchProcess<A, B>> : std::true_type {};

  /**
     T1 and T2 are both references if possible (lvalue), otherwise