ForEachAssociatedGroup.h

Go to the documentation of this file.

#ifndef LARDATA_UTILITIES_FOR_EACH_ASSOCIATED_GROUP_H
#define LARDATA_UTILITIES_FOR_EACH_ASSOCIATED_GROUP_H

// LArSoft libraries
#include "lardata/Utilities/RangeForWrapper.h"

// framework libraries
#include "canvas/Persistency/Common/AssnsAlgorithms.h" // art::for_each_group()

// range library
#include "range/v3/algorithm/for_each.hpp"
#include "range/v3/view/all.hpp"
#include "range/v3/view/group_by.hpp"
#include "range/v3/view/map.hpp" // range::views::values
#include "range/v3/view/transform.hpp"

// C/C++ standard libraries
#include <iterator> // std::next()
#include <utility>  // std::make_pair()

namespace util {
  template <class A, class F>
  [[deprecated("Use art::for_each_group() instead")]] void for_each_associated_group(A const& assns,
                                                                                     F& func)
  {
    art::for_each_group(assns, func);
  }

  template <class A>
  auto associated_groups(A const& assns)
  {
    return assns | ranges::views::all |
           ranges::views::chunk_by([](auto a1, auto a2) { return a1.first == a2.first; }) |
           ranges::views::transform(
             [](auto pairs) { return pairs | ranges::views::values | util::range_for; }) |
           util::range_for;
  } // associated_groups()

  template <class A>
  auto associated_groups_with_left(A const& assns)
  {
    return assns | ranges::views::all |
           ranges::views::chunk_by([](auto a1, auto a2) { return a1.first == a2.first; }) |
           ranges::views::transform([](auto pairs) {
             return std::make_pair(pairs.front().first, // assuming they're all the same, pick first
                                   pairs | ranges::views::values | util::range_for);
           }) |
           util::range_for;
  } // associated_groups_with_left()

  template <typename Groups>
  auto groupByIndex(Groups&& groups, std::size_t index) -> decltype(auto)
  {
    return *(std::next(groups.begin(), index));
  }

} // namespace util

#endif // LARDATA_UTILITIES_FOR_EACH_ASSOCIATED_GROUP_H