ParticleRange.hpp

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/*
 * Copyright (C) 2010-2022 The ESPResSo project
 *
 * This file is part of ESPResSo.
 *
 * ESPResSo is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * ESPResSo is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
#pragma once
 
#include "CellParticleIterator.hpp"
#include "Particle.hpp"
#include "ParticleIterator.hpp"
#include "PropagationPredicate.hpp"
#include "cell_system/Cell.hpp"
 
#include <boost/range/iterator_range.hpp>
 
#include <cassert>
 
/**
 * @brief A range of particles.
 *
 * This is a boost::iterator_range with the addition that the
 * size of the range is cached.
 */
class ParticleRange : public boost::iterator_range<CellParticleIterator> {
  using base_type = boost::iterator_range<CellParticleIterator>;
 
public:
  using base_type::base_type;
 
  base_type::size_type size() const {
    if (m_size < 0) {
      m_size = distance(begin(), end());
    }
 
    return assert(m_size >= 0), static_cast<base_type::size_type>(m_size);
  }
 
  template <typename Predicate>
  ParticleRangeFiltered<Predicate> filter(Predicate pred) const {
    auto const predicate = PropagationPredicate<Predicate>(pred);
    return {boost::make_filter_iterator(predicate, begin(), end()),
            boost::make_filter_iterator(predicate, end(), end())};
  }
 
private:
  base_type::difference_type mutable m_size = -1;
};