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#pragma once
#include <util/generic/store_policy.h>
#include <algorithm>
#include <tuple>
namespace NPrivate {
template <typename TContainer, typename TIteratorCategory = typename std::iterator_traits<decltype(std::begin(std::declval<TContainer>()))>::iterator_category>
static constexpr bool HasRandomAccessIterator(int32_t) {
return std::is_same_v<TIteratorCategory, std::random_access_iterator_tag>;
}
template <typename TContainer>
static constexpr bool HasRandomAccessIterator(uint32_t) {
return false;
}
template <typename... TContainers>
struct TZipper {
template <std::size_t... I>
struct TZipperWithIndex {
private:
using THolders = std::tuple<TAutoEmbedOrPtrPolicy<TContainers>...>;
using TValue = std::tuple<decltype(*std::begin(std::declval<TContainers&>()))...>;
using TIteratorState = std::tuple<decltype(std::begin(std::declval<TContainers&>()))...>;
using TSentinelState = std::tuple<decltype(std::end(std::declval<TContainers&>()))...>;
static constexpr bool TrivialSentinel = std::is_same_v<TIteratorState, TSentinelState>;
struct TIterator;
struct TSentinelCandidate {
TSentinelState Iterators_;
};
using TSentinel = std::conditional_t<TrivialSentinel, TIterator, TSentinelCandidate>;
#ifndef _MSC_VER
// windows compiler crashes here
static constexpr bool LimitByFirstContainer = TrivialSentinel &&
((HasRandomAccessIterator<TContainers>(0)) && ...);
#else
static constexpr bool LimitByFirstContainer = false;
#endif
struct TIterator {
using difference_type = std::ptrdiff_t;
using value_type = TValue;
using pointer = TValue*;
using reference = TValue&;
using const_reference = const TValue&;
using iterator_category = std::input_iterator_tag;
TValue operator*() {
return {*std::get<I>(Iterators_)...};
}
TValue operator*() const {
return {*std::get<I>(Iterators_)...};
}
TIterator& operator++() {
(++std::get<I>(Iterators_), ...);
return *this;
}
TIterator operator++(int) {
return TIterator{TIteratorState{std::get<I>(Iterators_)++...}};
}
bool operator!=(const TSentinel& other) const {
if constexpr (LimitByFirstContainer) {
return std::get<0>(Iterators_) != std::get<0>(other.Iterators_);
} else {
// yes, for all correct iterators but end() it is a correct way to compare
return ((std::get<I>(Iterators_) != std::get<I>(other.Iterators_)) && ...);
}
}
bool operator==(const TSentinel& other) const {
return !(*this != other);
}
TIteratorState Iterators_;
};
public:
using iterator = TIterator;
using const_iterator = TIterator;
using value_type = typename TIterator::value_type;
using reference = typename TIterator::reference;
using const_reference = typename TIterator::const_reference;
TIterator begin() const {
return {TIteratorState{std::begin(*std::get<I>(Holders_).Ptr())...}};
}
TSentinel end() const {
if constexpr (LimitByFirstContainer) {
auto endOfFirst = std::begin(*std::get<0>(Holders_).Ptr()) + std::min({
std::end(*std::get<I>(Holders_).Ptr()) - std::begin(*std::get<I>(Holders_).Ptr())...});
TIterator iter{TSentinelState{std::end(*std::get<I>(Holders_).Ptr())...}};
std::get<0>(iter.Iterators_) = endOfFirst;
return iter;
} else {
return {TSentinelState{std::end(*std::get<I>(Holders_).Ptr())...}};
}
}
mutable THolders Holders_;
};
template <std::size_t... I>
static auto Zip(TContainers&&... containers, std::index_sequence<I...>) {
return TZipperWithIndex<I...>{{std::forward<TContainers>(containers)...}};
}
};
}
//! Acts as pythonic zip, BUT result length is equal to shortest length of input containers
//! Usage: for (auto [ai, bi, ci] : Zip(a, b, c)) {...}
template <typename... TContainers>
auto Zip(TContainers&&... containers) {
return ::NPrivate::TZipper<TContainers...>::Zip(
std::forward<TContainers>(containers)...,
std::make_index_sequence<sizeof...(TContainers)>{}
);
}
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