IntListOperations.hpp

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#ifndef _INT_LIST_OPERATIONS_HPP
#define _INT_LIST_OPERATIONS_HPP

/// \file IntListOperations.hpp
///
/// \brief Implements operations over list of integers

namespace SUNphi
{
  /// Sum of all integers
  ///
  /// Internal implementation
  template <int...Ints>
  constexpr int _hSum()
  {
    if constexpr(sizeof...(Ints)==0)
      return 0;
    else
      return (Ints + ...);
  }

  /// Sum of all integers
  template <int...Ints>
  [[ maybe_unused ]]
  constexpr int hSum=
    _hSum<Ints...>();

  /////////////////////////////////////////////////////////////////

  /// Sum of all integers up to I (excluded)
  template <int I,
        int Head=0,
        int...Tail>
  [[ maybe_unused ]]
  constexpr int hSumFirst=
    (I>0)*Head+hSumFirst<I-1,Tail...>;

  /// Sum of all integers up to I (excluded),unary case
  template <int I,
        int Head>
  constexpr int hSumFirst<I,Head> =
    (I>0)*Head;

  /////////////////////////////////////////////////////////////////

  /// Product of all integers
  ///
  /// Internal implementation
  template <int...Ints>
  [[ maybe_unused ]]
  constexpr int _hMul()
  {
    if constexpr(sizeof...(Ints)==0)
      return 1;
    else
      return (Ints * ...);
  }

  /// Product of all integers
  template <int...Ints>
  [[ maybe_unused ]]
  constexpr int hMul=
    _hMul<Ints...>();

  /////////////////////////////////////////////////////////////////

  /// Provide a routine to search the minimal or maximal
#define DEFINE_SEARCH_MIN_OR_MAX(NAME,
                 DESCR,
                 OPER)
  /*! DESCR of all integers   */
  /*!                         */
  /*! Internal implementation */
  template <int In,
        int Head,
        int...Tail>
  int _ ## NAME ## OfList()
  {
    /* Binary comparison */
    constexpr int Tmp=(In OPER Head)?In:Head;

    /* Decide to return or nest */
    if constexpr(sizeof...(Tail)==0)
      return Tmp;
    else
      return _ ## NAME ## OfList<Tmp,Tail...>;
  }

  /*! DESCR of all integers */
  template <int Head,
        int...Tail>
  [[ maybe_unused ]]
  constexpr int NAME ## OfList=
    _ ## NAME ## OfList<Head,Head,Tail...>()

  DEFINE_SEARCH_MIN_OR_MAX(max,Maximal,>);
  DEFINE_SEARCH_MIN_OR_MAX(min,Minimal,<);

#undef DEFINE_SEARCH_MIN_OR_MAX
}

#endif