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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 <tuple>
#include <utility>
/* -------------------------------------------------------------------------- */
#ifndef __AKANTU_AKA_ITERATORS_HH__
#define __AKANTU_AKA_ITERATORS_HH__
namespace akantu {
namespace tuple {
/* ------------------------------------------------------------------------ */
namespace details {
template <size_t N> struct Foreach {
template <class Tuple>
static inline bool not_equal(Tuple && a, Tuple && b) {
if (std::get<N - 1>(std::forward<Tuple>(a)) ==
std::get<N - 1>(std::forward<Tuple>(b)))
return false;
return Foreach<N - 1>::not_equal(std::forward<Tuple>(a),
std::forward<Tuple>(b));
}
};
/* ---------------------------------------------------------------------- */
template <> struct Foreach<0> {
template <class Tuple>
static inline bool not_equal(Tuple && a, Tuple && b) {
return std::get<0>(std::forward<Tuple>(a)) !=
std::get<0>(std::forward<Tuple>(b));
}
};
template <typename... Ts>
decltype(auto) make_tuple_no_decay(Ts &&... args) {
return std::tuple<Ts...>(std::forward<Ts>(args)...);
}
template <class F, class Tuple, size_t... Is>
void foreach_impl(F && func, Tuple && tuple,
std::index_sequence<Is...> &&) {
(void)std::initializer_list<int>{
(std::forward<F>(func)(std::get<Is>(std::forward<Tuple>(tuple))),
0)...};
}
template <class F, class Tuple, size_t... Is>
decltype(auto) transform_impl(F && func, Tuple && tuple,
std::index_sequence<Is...> &&) {
return make_tuple_no_decay(
std::forward<F>(func)(std::get<Is>(std::forward<Tuple>(tuple)))...);
}
} // namespace details
/* ------------------------------------------------------------------------ */
template <class Tuple> bool are_not_equal(Tuple && a, Tuple && b) {
return details::Foreach<std::tuple_size<std::decay_t<Tuple>>::value>::
not_equal(std::forward<Tuple>(a), std::forward<Tuple>(b));
}
template <class F, class Tuple> void foreach (F && func, Tuple && tuple) {
return details::foreach_impl(
std::forward<F>(func), std::forward<Tuple>(tuple),
std::make_index_sequence<
std::tuple_size<std::decay_t<Tuple>>::value>{});
}
template <class F, class Tuple>
decltype(auto) transform(F && func, Tuple && tuple) {
return details::transform_impl(
std::forward<F>(func), std::forward<Tuple>(tuple),
std::make_index_sequence<
std::tuple_size<std::decay_t<Tuple>>::value>{});
}
} // namespace tuple
/* -------------------------------------------------------------------------- */
namespace iterators {
namespace {
template <typename It, typename category>
struct is_at_least_category
: std::is_same<std::common_type_t<
typename std::iterator_traits<It>::iterator_category,
category>,
category> {};
}
template <class... Iterators> class ZipIterator {
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...>;
private:
using tuple_t = std::tuple<Iterators...>;
public:
explicit ZipIterator(tuple_t iterators) : iterators(std::move(iterators)) {}
// input iterator ++it
ZipIterator & operator++() {
tuple::foreach ([](auto && it) { ++it; }, iterators);
return *this;
}
// input iterator it++
ZipIterator operator++(int) {
auto cpy = *this;
tuple::foreach ([](auto && it) { ++it; }, iterators);
return cpy;
}
// input iterator it != other_it
bool operator!=(const ZipIterator & other) const {
return tuple::are_not_equal(iterators, other.iterators);
}
// input iterator dereference *it
decltype(auto) operator*() {
return tuple::transform([](auto && it) -> decltype(auto) { return *it; },
iterators);
}
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)));
}
private:
containers_t containers;
};
template <class Iterator> class Range {
public:
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::input_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>;
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);
}
/* -------------------------------------------------------------------------- */
template <class Container>
inline constexpr decltype(auto) enumerate(Container && container,
size_t start_ = 0) {
auto stop = std::forward<Container>(container).size();
decltype(stop) start = start_;
return zip(arange(start, stop), std::forward<Container>(container));
}
} // namespace akantu
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;
};
}
#endif /* __AKANTU_AKA_ITERATORS_HH__ */
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