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aka_iterators.hh
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/**
* @file aka_iterators.hh
*
* @author Nicolas Richart
*
* @date creation Wed Jul 19 2017
*
* @brief iterator interfaces
*
* @section LICENSE
*
* Copyright (©) 2010-2011 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_error.hh"
/* -------------------------------------------------------------------------- */
#include <cassert>
#include <iostream>
#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 F, class Tuple>
static inline decltype(auto) transform_forward(F && func,
Tuple && tuple) {
return std::tuple_cat(
Foreach<N - 1>::transform_forward(std::forward<F>(func),
std::forward<Tuple>(tuple)),
std::forward_as_tuple(std::forward<F>(func)(
std::get<N - 1>(std::forward<Tuple>(tuple)))));
}
template <class F, class Tuple>
static inline decltype(auto) transform(F && func, Tuple && tuple) {
return std::tuple_cat(
Foreach<N - 1>::transform(std::forward<F>(func),
std::forward<Tuple>(tuple)),
std::make_tuple(std::forward<F>(func)(
std::get<N - 1>(std::forward<Tuple>(tuple)))));
}
template <class F, class Tuple>
static inline void foreach (F && func, Tuple && tuple) {
Foreach<N - 1>::foreach (std::forward<F>(func),
std::forward<Tuple>(tuple));
std::forward<F>(func)(std::get<N - 1>(std::forward<Tuple>(tuple)));
}
template <class Tuple> static inline bool equal(Tuple && a, Tuple && b) {
if (not(std::get<N - 1>(std::forward<Tuple>(a)) ==
std::get<N - 1>(std::forward<Tuple>(b))))
return false;
return Foreach<N - 1>::equal(std::forward<Tuple>(a),
std::forward<Tuple>(b));
}
};
/* ------------------------------------------------------------------------
*/
template <> struct Foreach<1> {
template <class F, class Tuple>
static inline decltype(auto) transform_forward(F && func,
Tuple && tuple) {
return std::forward_as_tuple(
std::forward<F>(func)(std::get<0>(std::forward<Tuple>(tuple))));
}
template <class F, class Tuple>
static inline decltype(auto) transform(F && func, Tuple && tuple) {
return std::make_tuple(
std::forward<F>(func)(std::get<0>(std::forward<Tuple>(tuple))));
}
template <class F, class Tuple>
static inline void foreach (F && func, Tuple && tuple) {
std::forward<F>(func)(std::get<0>(std::forward<Tuple>(tuple)));
}
template <class Tuple> static inline bool equal(Tuple && a, Tuple && b) {
return std::get<0>(std::forward<Tuple>(a)) ==
std::get<0>(std::forward<Tuple>(b));
}
};
} // namespace details
/* ------------------------------------------------------------------------ */
template <class Tuple> bool are_equal(Tuple && a, Tuple && b) {
return details::Foreach<std::tuple_size<std::decay_t<Tuple>>::value>::equal(
std::forward<Tuple>(a), std::forward<Tuple>(b));
}
template <class F, class Tuple> void foreach (F && func, Tuple && tuple) {
details::Foreach<std::tuple_size<std::decay_t<Tuple>>::value>::foreach (
std::forward<F>(func), std::forward<Tuple>(tuple));
}
template <class F, class Tuple>
decltype(auto) transform_forward(F && func, Tuple && tuple) {
return details::Foreach<std::tuple_size<std::decay_t<Tuple>>::value>::
transform_forward(std::forward<F>(func), std::forward<Tuple>(tuple));
}
template <class F, class Tuple>
decltype(auto) transform(F && func, Tuple && tuple) {
return details::Foreach<std::tuple_size<std::decay_t<Tuple>>::value>::
transform(std::forward<F>(func), std::forward<Tuple>(tuple));
}
} // namespace tuple
namespace iterators {
namespace details {
struct dereference_iterator {
template <class Iter> decltype(auto) operator()(Iter & it) const {
return std::forward<decltype(*it)>(*it);
}
};
struct increment_iterator {
template <class Iter> void operator()(Iter & it) const { ++it; }
};
struct begin_container {
template <class Container>
decltype(auto) operator()(Container && cont) const {
return std::forward<Container>(cont).begin();
}
};
struct end_container {
template <class Container>
decltype(auto) operator()(Container && cont) const {
return std::forward<Container>(cont).end();
}
};
} // namespace details
/* ------------------------------------------------------------------------ */
template <class... Iterators> class ZipIterator {
private:
using tuple_t = std::tuple<Iterators...>;
public:
explicit ZipIterator(tuple_t iterators) : iterators(std::move(iterators)) {}
decltype(auto) operator*() {
return tuple::transform_forward(details::dereference_iterator(),
iterators);
}
ZipIterator & operator++() {
tuple::foreach (details::increment_iterator(), iterators);
return *this;
}
bool operator==(const ZipIterator & other) const {
return tuple::are_equal(iterators, other.iterators);
}
bool operator!=(const ZipIterator & other) const {
return not operator==(other);
}
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(iterators::details::begin_container(),
std::forward<containers_t>(containers)));
}
decltype(auto) end() const {
return zip_iterator(
tuple::transform(iterators::details::end_container(),
std::forward<containers_t>(containers)));
}
decltype(auto) begin() {
return zip_iterator(
tuple::transform(iterators::details::begin_container(),
std::forward<containers_t>(containers)));
}
decltype(auto) end() {
return zip_iterator(
tuple::transform(iterators::details::end_container(),
std::forward<containers_t>(containers)));
}
private:
containers_t containers;
};
} // namespace containers
/* -------------------------------------------------------------------------- */
template <class... Containers> decltype(auto) zip(Containers &&... conts) {
return containers::ZipContainer<Containers...>(
std::forward<Containers>(conts)...);
}
/* -------------------------------------------------------------------------- */
/* Arange */
/* -------------------------------------------------------------------------- */
namespace iterators {
template <class T> class ArangeIterator {
public:
using value_type = T;
using pointer = T *;
using reference = 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 const 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 size_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> inline decltype(auto) arange(T stop) {
return containers::ArangeContainer<T>(stop);
}
template <class T>
inline constexpr decltype(auto) arange(T start, T stop, T step = 1) {
return containers::ArangeContainer<T>(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
#endif /* __AKANTU_AKA_ITERATORS_HH__ */

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