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/group_by.hpp"
#include "range/v3/view/transform.hpp"
#include "range/v3/view/map.hpp" // range::view::values
#include "range/v3/view/all.hpp"

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


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::view::all |
            ranges::view::group_by([](auto a1, auto a2) { return a1.first == a2.first;}) |
            ranges::view::transform([] (auto pairs) {return pairs | ranges::view::values | util::range_for;}) |
            util::range_for
            ;
  } // associated_groups()


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