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libmultiscale/include/iterators/aka_arange_iterator.hh
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aka_arange_iterator.hh
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/**
* @file aka_arange_iterator.hh
*
* @author Nicolas Richart
*
* @date creation jeu déc 12 2019
*
* @brief implementation of arange
*
* @section LICENSE
*
* Copyright (©) 2010-2011 EPFL (Ecole Polytechnique Fédérale de Lausanne)
* Laboratory (LSMS - Laboratoire de Simulation en Mécanique des Solides)
*
* akantu-iterators 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-iterators 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-iterators. If not, see <http://www.gnu.org/licenses/>.
*
*/
/* -------------------------------------------------------------------------- */
#include <cstddef>
#include <iterator>
#include <utility>
/* -------------------------------------------------------------------------- */
#ifndef AKA_ARANGE_ITERATOR_HH
#define AKA_ARANGE_ITERATOR_HH
#ifndef AKANTU_ITERATORS_NAMESPACE
#define AKANTU_ITERATORS_NAMESPACE akantu
#endif
namespace AKANTU_ITERATORS_NAMESPACE {
namespace 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 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[](std::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 AKANTU_ITERATORS_NAMESPACE
namespace std {
template <class T>
struct iterator_traits<
::AKANTU_ITERATORS_NAMESPACE::iterators::ArangeIterator<T>> {
private:
using iterator_type =
typename ::AKANTU_ITERATORS_NAMESPACE::iterators::ArangeIterator<T>;
public:
using iterator_category = typename iterator_type::iterator_category;
using value_type = typename iterator_type::value_type;
using difference_type = typename iterator_type::difference_type;
using pointer = typename iterator_type::pointer;
using reference = typename iterator_type::reference;
};
} // namespace std
#endif /* AKA_ARANGE_ITERATOR_HH */
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