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slice.hpp
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#ifndef ITER_SLICE_HPP_
#define ITER_SLICE_HPP_
#include "internal/iterbase.hpp"
#include <iterator>
#include <type_traits>
#include <initializer_list>
namespace iter {
namespace impl {
template <typename Container, typename DifferenceType>
class Sliced;
}
template <typename Container, typename DifferenceType>
impl::Sliced<Container, DifferenceType> slice(Container&& container,
DifferenceType start, DifferenceType stop, DifferenceType step = 1);
template <typename Container, typename DifferenceType>
impl::Sliced<Container, DifferenceType> slice(
Container&& container, DifferenceType stop);
template <typename T, typename DifferenceType>
impl::Sliced<std::initializer_list<T>, DifferenceType> slice(
std::initializer_list<T> il, DifferenceType start, DifferenceType stop,
DifferenceType step = 1);
template <typename T, typename DifferenceType>
impl::Sliced<std::initializer_list<T>, DifferenceType> slice(
std::initializer_list<T> il, DifferenceType stop);
}
template <typename Container, typename DifferenceType>
class iter::impl::Sliced {
private:
Container container;
DifferenceType start;
DifferenceType stop;
DifferenceType step;
friend Sliced iter::slice<Container, DifferenceType>(
Container&&, DifferenceType, DifferenceType, DifferenceType);
friend Sliced iter::slice<Container, DifferenceType>(
Container&&, DifferenceType);
Sliced(Container&& in_container, DifferenceType in_start,
DifferenceType in_stop, DifferenceType in_step)
: container(std::forward<Container>(in_container)),
start{in_start < in_stop && in_step > 0 ? in_start : in_stop},
stop{in_stop},
step{in_step} {}
public:
Sliced(Sliced&&) = default;
class Iterator : public std::iterator<std::input_iterator_tag,
iterator_traits_deref<Container>> {
private:
iterator_type<Container> sub_iter;
iterator_type<Container> sub_end;
DifferenceType current;
DifferenceType stop;
DifferenceType step;
public:
Iterator(iterator_type<Container>&& si, iterator_type<Container>&& se,
DifferenceType in_start, DifferenceType in_stop, DifferenceType in_step)
: sub_iter{std::move(si)},
sub_end{std::move(se)},
current{in_start},
stop{in_stop},
step{in_step} {}
iterator_deref<Container> operator*() {
return *this->sub_iter;
}
iterator_arrow<Container> operator->() {
return apply_arrow(this->sub_iter);
}
Iterator& operator++() {
dumb_advance(this->sub_iter, this->sub_end, this->step);
this->current += this->step;
if (this->stop < this->current) {
this->current = this->stop;
}
return *this;
}
Iterator operator++(int) {
auto ret = *this;
++*this;
return ret;
}
bool operator!=(const Iterator& other) const {
return this->sub_iter != other.sub_iter && this->current != other.current;
}
bool operator==(const Iterator& other) const {
return !(*this != other);
}
};
Iterator begin() {
auto it = std::begin(this->container);
dumb_advance(it, std::end(this->container), this->start);
return {std::move(it), std::end(this->container), this->start, this->stop,
this->step};
}
Iterator end() {
return {std::end(this->container), std::end(this->container), this->stop,
this->stop, this->step};
}
};
// Helper function to instantiate a Sliced
template <typename Container, typename DifferenceType>
iter::impl::Sliced<Container, DifferenceType> iter::slice(Container&& container,
DifferenceType start, DifferenceType stop, DifferenceType step) {
return {std::forward<Container>(container), start, stop, step};
}
// only give the end as an arg and assume step is 1 and begin is 0
template <typename Container, typename DifferenceType>
iter::impl::Sliced<Container, DifferenceType> iter::slice(
Container&& container, DifferenceType stop) {
return {std::forward<Container>(container), 0, stop, 1};
}
template <typename T, typename DifferenceType>
iter::impl::Sliced<std::initializer_list<T>, DifferenceType> iter::slice(
std::initializer_list<T> il, DifferenceType start, DifferenceType stop,
DifferenceType step) {
return {std::move(il), start, stop, step};
}
template <typename T, typename DifferenceType>
iter::impl::Sliced<std::initializer_list<T>, DifferenceType> iter::slice(
std::initializer_list<T> il, DifferenceType stop) {
return {std::move(il), 0, stop, 1};
}
#endif