mesh_iterator.hpp

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// Copyright (c) 2016-2018 Commissariat à l'énergie atomique et aux énergies alternatives (CEA)
// Copyright (c) 2016-2018 Centre national de la recherche scientifique (CNRS)
// Copyright (c) 2018-2023 Simons Foundation
//
// This program 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.
//
// This program 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 may obtain a copy of the License at
//     https://www.gnu.org/licenses/gpl-3.0.txt
//
// Authors: Thomas Ayral, Philipp Dumitrescu, Michel Ferrero, Olivier Parcollet, Nils Wentzell

 
#pragma once
 
#include "../utility/macros.hpp"
 
#include <compare>
#include <cstddef>
#include <iterator>
 
namespace triqs::mesh {

  template <typename M> struct C2PY_IGNORE mesh_iterator {
    using value_type = typename M::mesh_point_t;

    using iterator_category = std::random_access_iterator_tag;

    using pointer = value_type *;

    using difference_type = std::ptrdiff_t;

    using reference = value_type const &;

    M const *mesh_ptr{nullptr};

    long data_index{-1};

    mesh_iterator &operator++() noexcept {
      ++data_index;
      return *this;
    }

    mesh_iterator operator++(int) noexcept {
      mesh_iterator tmp = *this;
      ++data_index;
      return tmp;
    }

    mesh_iterator &operator--() noexcept {
      --data_index;
      return *this;
    }

    mesh_iterator operator--(int) noexcept {
      mesh_iterator tmp = *this;
      --data_index;
      return tmp;
    }

    [[nodiscard]] std::strong_ordering operator<=>(mesh_iterator const &rhs) const noexcept { return data_index <=> rhs.data_index; }

    [[nodiscard]] bool operator==(mesh_iterator const &other) const noexcept { return mesh_ptr == other.mesh_ptr and data_index == other.data_index; }

    [[nodiscard]] value_type operator*() const noexcept { return mesh_ptr->operator[](data_index); }

    [[nodiscard]] value_type operator->() const noexcept { return operator*(); }

    mesh_iterator &operator+=(difference_type n) noexcept {
      data_index += n;
      return *this;
    }

    [[nodiscard]] mesh_iterator operator+(difference_type n) const noexcept { return {.mesh_ptr = mesh_ptr, .data_index = data_index + n}; }

    [[nodiscard]] C2PY_IGNORE friend mesh_iterator operator+(difference_type n, mesh_iterator it) noexcept { return it + n; }

    mesh_iterator &operator-=(difference_type n) noexcept {
      data_index -= n;
      return *this;
    }

    [[nodiscard]] mesh_iterator operator-(difference_type n) const noexcept { return {.mesh_ptr = mesh_ptr, .data_index = data_index - n}; }

    [[nodiscard]] difference_type operator-(mesh_iterator const &rhs) const noexcept { return data_index - rhs.data_index; }

    [[nodiscard]] value_type operator[](difference_type n) const noexcept { return mesh_ptr->operator[](data_index + n); }
  };
 
} // namespace triqs::mesh