aka_iterators.hh
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aka_iterators.hh
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	/**
	* @file aka_iterators.hh
	*
	* @author Nicolas Richart <nicolas.richart@epfl.ch>
	*
	* @date creation: Fri Aug 11 2017
	* @date last modification: Mon Jan 29 2018
	*
	* @brief iterator interfaces
	*
	* @section LICENSE
	*
	* Copyright (©) 2016-2018 EPFL (Ecole Polytechnique Fédérale de Lausanne)
	* Laboratory (LSMS - Laboratoire de Simulation en Mécanique des Solides)
	*
	* Akantu is free software: you can redistribute it and/or modify it under the
	* terms of the GNU Lesser General Public License as published by the Free
	* Software Foundation, either version 3 of the License, or (at your option) any
	* later version.
	*
	* Akantu 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 Lesser General Public License for more
	* details.
	*
	* You should have received a copy of the GNU Lesser General Public License
	* along with Akantu. If not, see <http://www.gnu.org/licenses/>.
	*
	*/

	/* -------------------------------------------------------------------------- */
	#include "aka_compatibilty_with_cpp_standard.hh"
	#include "aka_tuple_tools.hh"
	/* -------------------------------------------------------------------------- */
	#include <iterator>
	#include <tuple>
	#include <utility>

	/* -------------------------------------------------------------------------- */
	#ifndef AKANTU_AKA_ITERATORS_HH
	#define AKANTU_AKA_ITERATORS_HH

	#ifndef AKANTU_ITERATOR_NAMESPACE
	#define AKANTU_ITERATOR_NAMESPACE akantu
	#endif

	namespace AKANTU_ITERATOR_NAMESPACE {

	/* -------------------------------------------------------------------------- */
	namespace iterators {
	namespace details {
	template <typename cat1, typename cat2>
	using is_iterator_category_at_least =
	std::is_same<std::common_type_t<cat1, cat2>, cat2>;
	}

	template <class... Iterators> class ZipIterator {
	private:
	using tuple_t = std::tuple<Iterators...>;

	public:
	using value_type =
	std::tuple<typename std::iterator_traits<Iterators>::value_type...>;
	using difference_type = std::common_type_t<
	typename std::iterator_traits<Iterators>::difference_type...>;
	using pointer =
	std::tuple<typename std::iterator_traits<Iterators>::pointer...>;
	using reference =
	std::tuple<typename std::iterator_traits<Iterators>::reference...>;
	using iterator_category = // std::input_iterator_tag;
	std::common_type_t<
	typename std::iterator_traits<Iterators>::iterator_category...>;

	using nb_iterators = std::tuple_size<tuple_t>;

	public:
	explicit ZipIterator(tuple_t iterators) : iterators(std::move(iterators)) {}

	ZipIterator(const ZipIterator & other) = default;
	ZipIterator(ZipIterator && other) noexcept = default;

	ZipIterator & operator=(const ZipIterator & other) = default;
	ZipIterator & operator=(ZipIterator && other) noexcept = default;

	/* ---------------------------------------------------------------------- */
	template <class iterator_category_ = iterator_category,
	std::enable_if_t<details::is_iterator_category_at_least<
	iterator_category_,
	std::bidirectional_iterator_tag>::value> * = nullptr>
	ZipIterator & operator--() {
	tuple::foreach ([](auto && it) { --it; }, iterators);
	return *this;
	}

	template <class iterator_category_ = iterator_category,
	std::enable_if_t<details::is_iterator_category_at_least<
	iterator_category_,
	std::bidirectional_iterator_tag>::value> * = nullptr>
	ZipIterator operator--(int a) {
	auto cpy = *this;
	this->operator--();
	return cpy;
	}

	// input iterator ++it
	ZipIterator & operator++() {
	tuple::foreach ([](auto && it) { ++it; }, iterators);
	return *this;
	}

	// input iterator it++
	ZipIterator operator++(int) {
	auto cpy = *this;
	this->operator++();
	return cpy;
	}

	// input iterator it != other_it
	bool operator!=(const ZipIterator & other) const {
	// return tuple::are_not_equal(iterators, other.iterators);
	return std::get<0>(iterators) !=
	std::get<0>(other.iterators); // helps the compiler to optimize
	}

	// input iterator dereference *it
	decltype(auto) operator*() {
	return tuple::transform([](auto && it) -> decltype(auto) { return *it; },
	iterators);
	}

	template <class iterator_category_ = iterator_category,
	std::enable_if_t<details::is_iterator_category_at_least<
	iterator_category_,
	std::random_access_iterator_tag>::value> * = nullptr>
	difference_type operator-(const ZipIterator & other) {
	return std::get<0>(this->iterators) - std::get<0>(other.iterators);
	}

	// random iterator it[idx]
	template <class iterator_category_ = iterator_category,
	std::enable_if_t<details::is_iterator_category_at_least<
	iterator_category_,
	std::random_access_iterator_tag>::value> * = nullptr>
	decltype(auto) operator[](std::size_t idx) {
	return tuple::transform(
	[idx](auto && it) -> decltype(auto) { return it[idx]; }, iterators);
	}

	// random iterator it + n
	template <class iterator_category_ = iterator_category,
	std::enable_if_t<details::is_iterator_category_at_least<
	iterator_category_,
	std::random_access_iterator_tag>::value> * = nullptr>
	decltype(auto) operator+(std::size_t n) {
	return ZipIterator(std::forward<tuple_t>(tuple::transform(
	[n](auto && it) -> decltype(auto) { return it + n; }, iterators)));
	}

	// random iterator it - n
	template <class iterator_category_ = iterator_category,
	std::enable_if_t<details::is_iterator_category_at_least<
	iterator_category_,
	std::random_access_iterator_tag>::value> * = nullptr>
	decltype(auto) operator-(std::size_t n) {
	return ZipIterator(std::forward<tuple_t>(tuple::transform(
	[n](auto && it) -> decltype(auto) { return it - n; }, iterators)));
	}

	template <
	class iterator_category_ = iterator_category,
	std::enable_if_t<details::is_iterator_category_at_least<
	iterator_category_, std::forward_iterator_tag>::value> * = nullptr>
	bool operator==(const ZipIterator & other) const {
	return not tuple::are_not_equal(iterators, other.iterators);
	}

	private:
	tuple_t iterators;
	};
	} // namespace iterators

	/* -------------------------------------------------------------------------- */
	template <class... Iterators>
	decltype(auto) zip_iterator(std::tuple<Iterators...> && iterators_tuple) {
	auto zip = iterators::ZipIterator<Iterators...>(
	std::forward<decltype(iterators_tuple)>(iterators_tuple));
	return zip;
	}

	/* -------------------------------------------------------------------------- */
	namespace containers {
	template <class... Containers> class ZipContainer {
	using containers_t = std::tuple<Containers...>;

	public:
	explicit ZipContainer(Containers &&... containers)
	: containers(std::forward<Containers>(containers)...) {}

	decltype(auto) begin() const {
	return zip_iterator(
	tuple::transform([](auto && c) { return c.begin(); },
	std::forward<containers_t>(containers)));
	}

	decltype(auto) end() const {
	return zip_iterator(
	tuple::transform([](auto && c) { return c.end(); },
	std::forward<containers_t>(containers)));
	}

	decltype(auto) begin() {
	return zip_iterator(
	tuple::transform([](auto && c) { return c.begin(); },
	std::forward<containers_t>(containers)));
	}

	decltype(auto) end() {
	return zip_iterator(
	tuple::transform([](auto && c) { return c.end(); },
	std::forward<containers_t>(containers)));
	}

	// template <class Container = std::tuple_element<0, containers_t>,
	// std::enable_if_t<std::is_integral<decltype(
	// std::declval<Container>().size())>::value> * = nullptr>
	// decltype(auto) size() {
	// return std::forward<Container>(std::get<0>(containers)).size();
	// }

	private:
	containers_t containers;
	};

	template <class Iterator> class Range {
	public:
	using iterator = Iterator;
	// ugly trick
	using const_iterator = Iterator;

	explicit Range(Iterator && it1, Iterator && it2)
	: iterators(std::forward<Iterator>(it1), std::forward<Iterator>(it2)) {}

	decltype(auto) begin() const { return std::get<0>(iterators); }
	decltype(auto) begin() { return std::get<0>(iterators); }

	decltype(auto) end() const { return std::get<1>(iterators); }
	decltype(auto) end() { return std::get<1>(iterators); }

	private:
	std::tuple<Iterator, Iterator> iterators;
	};
	} // namespace containers

	/* -------------------------------------------------------------------------- */
	template <class... Containers> decltype(auto) zip(Containers &&... conts) {
	return containers::ZipContainer<Containers...>(
	std::forward<Containers>(conts)...);
	}

	template <class Iterator>
	decltype(auto) range(Iterator && it1, Iterator && it2) {
	return containers::Range<Iterator>(std::forward<Iterator>(it1),
	std::forward<Iterator>(it2));
	}
	/* -------------------------------------------------------------------------- */
	/* Arange */
	/* -------------------------------------------------------------------------- */
	namespace iterators {
	template <class T> class ArangeIterator {
	public:
	using value_type = T;
	using pointer = T *;
	using reference = T &;
	using difference_type = size_t;
	using iterator_category = std::forward_iterator_tag;

	constexpr ArangeIterator(T value, T step) : value(value), step(step) {}
	constexpr ArangeIterator(const ArangeIterator &) = default;

	constexpr ArangeIterator & operator++() {
	value += step;
	return *this;
	}

	constexpr T operator*() const { return value; }

	constexpr bool operator==(const ArangeIterator & other) const {
	return (value == other.value) and (step == other.step);
	}

	constexpr bool operator!=(const ArangeIterator & other) const {
	return not operator==(other);
	}

	private:
	T value{0};
	const T step{1};
	};
	} // namespace iterators

	namespace containers {
	template <class T> class ArangeContainer {
	public:
	using iterator = iterators::ArangeIterator<T>;
	using const_iterator = iterators::ArangeIterator<T>;

	constexpr ArangeContainer(T start, T stop, T step = 1)
	: start(start), stop((stop - start) % step == 0
	? stop
	: start + (1 + (stop - start) / step) * step),
	step(step) {}
	explicit constexpr ArangeContainer(T stop) : ArangeContainer(0, stop, 1) {}

	constexpr T operator[](size_t i) {
	T val = start + i * step;
	assert(val < stop && "i is out of range");
	return val;
	}

	constexpr T size() { return (stop - start) / step; }

	constexpr iterator begin() { return iterator(start, step); }
	constexpr iterator end() { return iterator(stop, step); }

	private:
	const T start{0}, stop{0}, step{1};
	};
	} // namespace containers

	template <class T,
	typename = std::enable_if_t<std::is_integral<std::decay_t<T>>::value>>
	inline decltype(auto) arange(const T & stop) {
	return containers::ArangeContainer<T>(stop);
	}

	template <class T1, class T2,
	typename = std::enable_if_t<
	std::is_integral<std::common_type_t<T1, T2>>::value>>
	inline constexpr decltype(auto) arange(const T1 & start, const T2 & stop) {
	return containers::ArangeContainer<std::common_type_t<T1, T2>>(start, stop);
	}

	template <class T1, class T2, class T3,
	typename = std::enable_if_t<
	std::is_integral<std::common_type_t<T1, T2, T3>>::value>>
	inline constexpr decltype(auto) arange(const T1 & start, const T2 & stop,
	const T3 & step) {
	return containers::ArangeContainer<std::common_type_t<T1, T2, T3>>(
	start, stop, step);
	}

	/* -------------------------------------------------------------------------- */
	namespace iterators {
	template <class Iterator> class EnumerateIterator {
	public:
	using value_type =
	std::tuple<size_t, typename std::iterator_traits<Iterator>::value_type>;
	using difference_type = size_t;
	using pointer =
	std::tuple<size_t, typename std::iterator_traits<Iterator>::pointer>;
	using reference =
	std::tuple<size_t, typename std::iterator_traits<Iterator>::reference>;
	using iterator_category = std::input_iterator_tag;

	public:
	explicit EnumerateIterator(Iterator && iterator) : iterator(iterator) {}

	// input iterator ++it
	EnumerateIterator & operator++() {
	++iterator;
	++index;
	return *this;
	}

	// input iterator it++
	EnumerateIterator operator++(int) {
	auto cpy = *this;
	this->operator++();
	return cpy;
	}

	// input iterator it != other_it
	bool operator!=(const EnumerateIterator & other) const {
	return iterator != other.iterator;
	}

	// input iterator dereference *it
	decltype(auto) operator*() {
	return std::tuple_cat(std::make_tuple(index), *iterator);
	}

	bool operator==(const EnumerateIterator & other) const {
	return not this->operator!=(other);
	}

	private:
	Iterator iterator;
	size_t index{0};
	};

	template <class Iterator>
	inline constexpr decltype(auto) enumerate(Iterator && iterator) {
	return EnumerateIterator<Iterator>(std::forward<Iterator>(iterator));
	}

	} // namespace iterators

	namespace containers {
	template <class... Containers> class EnumerateContainer {
	public:
	explicit EnumerateContainer(Containers &&... containers)
	: zip_container(std::forward<Containers>(containers)...) {}

	decltype(auto) begin() {
	return iterators::enumerate(zip_container.begin());
	}

	decltype(auto) begin() const {
	return iterators::enumerate(zip_container.begin());
	}

	decltype(auto) end() { return iterators::enumerate(zip_container.end()); }

	decltype(auto) end() const {
	return iterators::enumerate(zip_container.end());
	}

	private:
	ZipContainer<Containers...> zip_container;
	};
	} // namespace containers

	template <class... Container>
	inline constexpr decltype(auto) enumerate(Container &&... container) {
	return containers::EnumerateContainer<Container...>(
	std::forward<Container>(container)...);
	}

	/* -------------------------------------------------------------------------- */
	/* -------------------------------------------------------------------------- */
	namespace iterators {
	template <class iterator_t, class operator_t>
	class transform_adaptor_iterator {
	public:
	using value_type = decltype(std::declval<operator_t>()(
	std::declval<typename iterator_t::value_type>()));
	using difference_type = typename iterator_t::difference_type;
	using pointer = std::decay_t<value_type> *;
	using reference = value_type &;
	using iterator_category = typename iterator_t::iterator_category;

	transform_adaptor_iterator(iterator_t it, operator_t op)
	: it(std::move(it)), op(op) {}
	transform_adaptor_iterator(const transform_adaptor_iterator &) = default;

	transform_adaptor_iterator & operator++() {
	++it;
	return *this;
	}

	decltype(auto) operator() { return op(std::forward<decltype(it)>(*it)); }

	bool operator==(const transform_adaptor_iterator & other) const {
	return (it == other.it);
	}

	bool operator!=(const transform_adaptor_iterator & other) const {
	return not operator==(other);
	}

	template <class iterator_category_ = iterator_category,
	std::enable_if_t<details::is_iterator_category_at_least<
	iterator_category_,
	std::random_access_iterator_tag>::value> * = nullptr>
	difference_type operator-(const transform_adaptor_iterator & other) {
	return other - *this;
	}

	private:
	iterator_t it;
	operator_t op;
	};

	template <class iterator_t, class operator_t>
	decltype(auto) make_transform_adaptor_iterator(iterator_t it, operator_t op) {
	return transform_adaptor_iterator<iterator_t, operator_t>(
	it, std::forward<operator_t>(op));
	}

	} // namespace iterators

	namespace containers {
	template <class container_t, class operator_t>
	class TransformIteratorAdaptor {
	public:
	// using const_iterator = typename
	// std::decay_t<container_t>::const_iterator; using iterator = typename
	// std::decay_t<container_t>::iterator;

	TransformIteratorAdaptor(container_t && cont, operator_t op)
	: cont(std::forward<container_t>(cont)),
	op(std::forward<operator_t>(op)) {}

	decltype(auto) begin() const {
	return iterators::make_transform_adaptor_iterator(cont.begin(), op);
	}
	decltype(auto) begin() {
	return iterators::make_transform_adaptor_iterator(cont.begin(), op);
	}

	decltype(auto) end() const {
	return iterators::make_transform_adaptor_iterator(cont.end(), op);
	}
	decltype(auto) end() {
	return iterators::make_transform_adaptor_iterator(cont.end(), op);
	}

	private:
	container_t cont;
	operator_t op;
	};
	} // namespace containers

	template <class container_t, class operator_t>
	decltype(auto) make_transform_adaptor(container_t && cont, operator_t && op) {
	return containers::TransformIteratorAdaptor<container_t, operator_t>(
	std::forward<container_t>(cont), std::forward<operator_t>(op));
	}

	template <class container_t>
	decltype(auto) make_keys_adaptor(container_t && cont) {
	return make_transform_adaptor(
	std::forward<container_t>(cont),
	[](auto && pair) -> const auto & { return pair.first; });
	}

	template <class container_t>
	decltype(auto) make_values_adaptor(container_t && cont) {
	return make_transform_adaptor(
	std::forward<container_t>(cont),
	[](auto && pair) -> auto & { return pair.second; });
	}

	template <class container_t>
	decltype(auto) make_dereference_adaptor(container_t && cont) {
	return make_transform_adaptor(
	std::forward<container_t>(cont),
	[](auto && value) -> decltype(value) { return value; });
	}

	template <class... zip_container_t>
	decltype(auto) make_zip_cat(zip_container_t &&... cont) {
	return make_transform_adaptor(
	zip(std::forward<zip_container_t>(cont)...),
	[](auto && value) { return tuple::flatten(value); });
	}

	/* -------------------------------------------------------------------------- */
	namespace iterators {
	template <class filter_iterator_t, class container_iterator_t>
	class FilterIterator {
	public:
	using value_type =
	decltype(std::declval<container_iterator_t>().operator[](0));
	using difference_type = typename filter_iterator_t::difference_type;
	using pointer = std::decay_t<value_type> *;
	using reference = value_type &;
	using iterator_category = typename filter_iterator_t::iterator_category;

	FilterIterator(filter_iterator_t filter_it,
	container_iterator_t container_begin)
	: filter_it(std::move(filter_it)), container_begin(container_begin),
	container_it(container_begin) {}

	FilterIterator(const FilterIterator &) = default;

	FilterIterator & operator++() {
	++filter_it;
	container_it =
	container_begin + *filter_it; // this might return invalid iterators
	return *this;
	}

	decltype(auto) operator() { return container_it; }

	decltype(auto) operator() const { return container_it; }

	bool operator==(const FilterIterator & other) const {
	return (filter_it == other.filter_it) and
	(container_begin == other.container_begin);
	}

	bool operator!=(const FilterIterator & other) const {
	return filter_it != other.filter_it;
	}

	private:
	filter_iterator_t filter_it;
	container_iterator_t container_begin;
	container_iterator_t container_it;
	};

	template <class filter_iterator_t, class container_iterator_t>
	decltype(auto) make_filter_iterator(filter_iterator_t && filter_it,
	container_iterator_t && container_begin) {
	return FilterIterator<filter_iterator_t, container_iterator_t>(
	std::forward<filter_iterator_t>(filter_it),
	std::forward<container_iterator_t>(container_begin));
	}
	} // namespace iterators

	namespace containers {
	template <class filter_t, class Container> class FilterAdaptor {
	public:
	FilterAdaptor(filter_t && filter, Container && container)
	: filter(std::forward<filter_t>(filter)),
	container(std::forward<Container>(container)) {
	static_assert(
	std::is_same<typename decltype(container.begin())::iterator_category,
	std::random_access_iterator_tag>::value,
	"Containers must all have random iterators");
	}

	decltype(auto) begin() const {
	return iterators::make_filter_iterator(filter.begin(), container.begin());
	}
	decltype(auto) begin() {
	return iterators::make_filter_iterator(filter.begin(), container.begin());
	}

	decltype(auto) end() const {
	return iterators::make_filter_iterator(filter.end(), container.begin());
	}
	decltype(auto) end() {
	return iterators::make_filter_iterator(filter.end(), container.begin());
	}

	private:
	filter_t filter;
	Container container;
	};
	} // namespace containers

	template <class filter_t, class Container>
	decltype(auto) filter(filter_t && filter, Container && container) {
	return containers::FilterAdaptor<filter_t, Container>(
	std::forward<filter_t>(filter), std::forward<Container>(container));
	}

	} // namespace AKANTU_ITERATOR_NAMESPACE

	namespace std {
	template <typename... Its>
	struct iterator_traits<::akantu::iterators::ZipIterator<Its...>> {
	using iterator_category = forward_iterator_tag;
	using value_type =
	typename ::akantu::iterators::ZipIterator<Its...>::value_type;
	using difference_type =
	typename ::akantu::iterators::ZipIterator<Its...>::difference_type;
	using pointer = typename ::akantu::iterators::ZipIterator<Its...>::pointer;
	using reference =
	typename ::akantu::iterators::ZipIterator<Its...>::reference;
	};

	} // namespace std

	#endif /* AKANTU_AKA_ITERATORS_HH */

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