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130 lines (106 loc) · 4.43 KB
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#ifndef ITER_ZIP_LONGEST_HPP_
#define ITER_ZIP_LONGEST_HPP_
#include "iterbase.hpp"
#include <boost/optional.hpp>
#include <iterator>
#include <tuple>
#include <utility>
namespace iter {
template <typename TupleType, std::size_t... Is>
class ZippedLongest;
template <typename TupleType, std::size_t... Is>
ZippedLongest<TupleType, Is...>
zip_longest_impl(TupleType&&, std::index_sequence<Is...>);
template <typename TupleType, std::size_t... Is>
class ZippedLongest {
private:
TupleType containers;
friend ZippedLongest zip_longest_impl<TupleType, Is...>(
TupleType&&, std::index_sequence<Is...>);
template <std::size_t I>
using OptType = boost::optional<iterator_deref<
std::tuple_element_t<I, TupleType>>>;
using ZipIterDeref = std::tuple<OptType<Is>...>;
ZippedLongest(TupleType&& in_containers)
: containers(std::move(in_containers))
{ }
public:
class Iterator
: public std::iterator<std::input_iterator_tag, ZipIterDeref>
{
private:
iterator_tuple_type<TupleType> iters;
iterator_tuple_type<TupleType> ends;
public:
Iterator(iterator_tuple_type<TupleType>&& in_iters,
iterator_tuple_type<TupleType>&& in_ends)
: iters(std::move(in_iters)),
ends(std::move(in_ends))
{ }
Iterator& operator++() {
// increment every iterator that's not already at
// the end
absorb(
((std::get<Is>(this->iters) !=
std::get<Is>(this->ends)) ?
(++std::get<Is>(this->iters), 0) : 0)...);
return *this;
}
Iterator operator++(int) {
auto ret = *this;
++*this;
return ret;
}
bool operator!=(const Iterator& other) const {
if (sizeof...(Is) == 0) return false;
bool results[] = { false,
(std::get<Is>(this->iters) !=
std::get<Is>(other.iters))...
};
return std::any_of(
std::begin(results), std::end(results),
[](bool b){ return b; } );
}
bool operator==(const Iterator& other) const {
return !(*this != other);
}
ZipIterDeref operator*() {
return ZipIterDeref{
((std::get<Is>(this->iters) !=
std::get<Is>(this->ends))
? OptType<Is>{*std::get<Is>(this->iters)}
: OptType<Is>{})...};
}
ArrowProxy<ZipIterDeref> operator->() {
return {**this};
}
};
Iterator begin() {
return {
iterator_tuple_type<TupleType>{
std::begin(std::get<Is>(this->containers))...},
iterator_tuple_type<TupleType>{
std::end(std::get<Is>(this->containers))...}};
}
Iterator end() {
return {
iterator_tuple_type<TupleType>{
std::end(std::get<Is>(this->containers))...},
iterator_tuple_type<TupleType>{
std::end(std::get<Is>(this->containers))...}};
}
};
template <typename TupleType, std::size_t... Is>
ZippedLongest<TupleType, Is...> zip_longest_impl(
TupleType&& in_containers, std::index_sequence<Is...>) {
return {std::move(in_containers)};
}
template <typename... Containers>
auto zip_longest(Containers&&... containers) {
return zip_longest_impl(
std::tuple<Containers...>{
std::forward<Containers>(containers)...},
std::index_sequence_for<Containers...>{});
}
}
#endif