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libmultiscale/include/iterators/aka_transform_iterator.hh
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aka_transform_iterator.hh
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/**
* @file aka_transform_iterator.hh
*
* @author Nicolas Richart
*
* @date creation jeu déc 12 2019
*
* @brief transform adaptors
*
* @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 <utility>
/* -------------------------------------------------------------------------- */
#ifndef AKA_TRANSFORM_ITERATOR_H
#define AKA_TRANSFORM_ITERATOR_H
#ifndef AKANTU_ITERATORS_NAMESPACE
#define AKANTU_ITERATORS_NAMESPACE akantu
#endif
namespace AKANTU_ITERATORS_NAMESPACE {
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<aka::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; });
}
} // namespace AKANTU_ITERATORS_NAMESPACE
#endif // AKA_TRANSFORM_ITERATOR_H
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