EvalVariadic.h

/**************************************************************************
 * basf2 (Belle II Analysis Software Framework)                           *
 * Author: The Belle II Collaboration                                     *
 *                                                                        *
 * See git log for contributors and copyright holders.                    *
 * This file is licensed under LGPL-3.0, see LICENSE.md.                  *
 **************************************************************************/
#pragma once
 
#include <tuple>
#include <type_traits>
 
namespace Belle2 {
  namespace TrackFindingCDC {

    template <class... Ts>
    static inline void evalVariadic(Ts&& ... expressions __attribute__((unused)))
    {
    }

    struct EvalVariadic {
      template <class... Ts>
      explicit EvalVariadic(Ts&& ... expressions __attribute__((unused)))
      {
      }
    };
 

    template<class... ATypes>
    struct FirstTypeImpl {
    };

    template<>
    struct FirstTypeImpl<> {
    };

    template<class AType>
    struct FirstTypeImpl<AType> {
      using Type = AType;
    };

    template<class AType, class... ATypes>
    struct FirstTypeImpl<AType, ATypes...> {
      using Type = AType;
    };

    template<class... ATypes>
    using FirstType = typename FirstTypeImpl<ATypes...>::Type;

    template<class AType, class ATuple>
    struct GetIndexInTuple {};

    template<class AType>
    struct GetIndexInTuple<AType, std::tuple<> > :
      std::integral_constant<std::size_t, 0> {};

    template<class AType, class AHeadType, class... ATailTypes>
    struct GetIndexInTuple<AType, std::tuple<AHeadType, ATailTypes...> > :
      std::integral_constant < std::size_t, GetIndexInTuple<AType, std::tuple<ATailTypes...> >::value + 1 > {};

    template<class AType, class... ATailTypes>
    struct GetIndexInTuple <AType, std::tuple<AType, ATailTypes...> > :
      std::integral_constant< std::size_t, 0> {};

    template<class T, class ATuple>
    using TypeInTuple =
      std::integral_constant < bool, (GetIndexInTuple<T, ATuple>::value < std::tuple_size<ATuple>::value) >;
 
  }
}