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C++ zip
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#include <cstdio> | |
#include <list> | |
#include <vector> | |
#include "zip.h" | |
int main() { | |
std::vector<int> one{{1, 11}}; | |
auto two = [] { return std::vector<short>{{2, 22}}; }; | |
const std::list<float> three{{3, 33}}; | |
std::vector<int> four{{4, 44}}; | |
for (auto a : zip(one, two(), three, four)) { | |
std::printf("%d %d %f %d\n", std::get<0>(a), std::get<short&>(a), | |
std::get<const float&>(a), std::get<3>(a)); | |
} | |
} |
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#include <iterator> | |
#include <tuple> | |
#include <utility> | |
template <typename... T> | |
class zip_helper { | |
public: | |
class iterator | |
: std::iterator<std::forward_iterator_tag, | |
std::tuple<decltype(*std::declval<T>().begin())...>> { | |
private: | |
std::tuple<decltype(std::declval<T>().begin())...> iters_; | |
template <std::size_t... I> | |
auto deref(std::index_sequence<I...>) const { | |
return typename iterator::value_type{*std::get<I>(iters_)...}; | |
} | |
template <std::size_t... I> | |
void increment(std::index_sequence<I...>) { | |
auto l = {(++std::get<I>(iters_), 0)...}; | |
} | |
public: | |
explicit iterator(decltype(iters_) iters) : iters_{std::move(iters)} {} | |
iterator& operator++() { | |
increment(std::index_sequence_for<T...>{}); | |
return *this; | |
} | |
iterator operator++(int) { | |
auto saved{*this}; | |
increment(std::index_sequence_for<T...>{}); | |
return saved; | |
} | |
bool operator!=(const iterator& other) const { | |
return iters_ != other.iters_; | |
} | |
auto operator*() const { return deref(std::index_sequence_for<T...>{}); } | |
}; | |
zip_helper(T&... seqs) | |
: begin_{std::make_tuple(seqs.begin()...)}, | |
end_{std::make_tuple(seqs.end()...)} {} | |
iterator begin() const { return begin_; } | |
iterator end() const { return end_; } | |
private: | |
iterator begin_; | |
iterator end_; | |
}; | |
// Sequences must be the same length. | |
template <typename... T> | |
auto zip(T&&... seqs) { | |
return zip_helper<T...>{seqs...}; | |
} |
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