zip_tuple.hpp

#include <cassert>
#include <functional>
#include <iomanip>
#include <iostream>
#include <list>
#include <string>
#include <vector>
#include <typeinfo>


namespace c9 {

template <typename Iter>
using select_access_type_for = std::conditional_t<
    std::is_same_v<Iter, std::vector<bool>::iterator> ||
    std::is_same_v<Iter, std::vector<bool>::const_iterator>,
    typename Iter::value_type,
    typename Iter::reference
>;


template <typename ... Args, std::size_t ... Index>
auto any_match_impl(std::tuple<Args...> const & lhs,
    std::tuple<Args...> const & rhs,
    std::index_sequence<Index...>) -> bool
{
    auto result = false;
    result = (... || (std::get<Index>(lhs) == std::get<Index>(rhs)));
    return result;
}


template <typename ... Args>
auto any_match(std::tuple<Args...> const & lhs, std::tuple<Args...> const & rhs)
    -> bool
{
    return any_match_impl(lhs, rhs, std::index_sequence_for<Args...>{});
}



template <typename ... Iters>
class zip_iterator
{
public:

    using value_type = std::tuple<
        select_access_type_for<Iters>...
    >;

    zip_iterator() = delete;

    zip_iterator(Iters && ... iters)
        : m_iters {std::forward<Iters>(iters)...}
    {
    }

    auto operator++() -> zip_iterator& 
    {
        std::apply([](auto && ... args){ ((args += 1), ...); }, m_iters);
        return *this;
    }

    auto operator++(int) -> zip_iterator 
    {
        auto tmp = *this;
        ++*this;
        return tmp;
    }

    auto operator!=(zip_iterator const & other) const
    {
        return !(*this == other);
    }

    auto operator==(zip_iterator const & other) const
    {
        auto result = false;
        return any_match(m_iters, other.m_iters);
    }

    auto operator*() -> value_type
    {
        return std::apply([](auto && ... args){ 
                return value_type(*args...); 
            }, m_iters);
    }

private:
    std::tuple<Iters...> m_iters;
};


/* std::decay needed because T is a reference, and is not a complete type */
template <typename T>
using select_iterator_for = std::conditional_t<
    std::is_const_v<std::remove_reference_t<T>>, 
    typename std::decay_t<T>::const_iterator,
    typename std::decay_t<T>::iterator>;



template <typename ... T>
class zipper
{
public:
    using zip_type = zip_iterator<select_iterator_for<T> ...>;

    template <typename ... Args>
    zipper(Args && ... args)
        : m_args{std::forward<Args>(args)...}
    {
    }

    auto begin() -> zip_type
    {
        return std::apply([](auto && ... args){ 
                return zip_type(std::begin(args)...); 
            }, m_args);
    }
    auto end() -> zip_type
    {
        return std::apply([](auto && ... args){ 
                return zip_type(std::end(args)...); 
            }, m_args);
    }

private:
    std::tuple<T ...> m_args;

};


template <typename ... T>
auto zip(T && ... t)
{
    return zipper<T ...>{std::forward<T>(t)...};
}

}