tuple.h

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#pragma once
 
#include <tuple>
 
namespace stdext {
 
namespace details {
template <class F, size_t... Is>
constexpr auto index_apply_impl(F f,
                                std::index_sequence<Is...>) {
    return f(std::integral_constant<size_t, Is> {}...);
}
 
template <size_t N, class F>
constexpr auto index_apply(F f) {
    return index_apply_impl(f, std::make_index_sequence<N>{});
}
}
 
template <typename Tuple>
constexpr auto pop_back(Tuple&& t) {
    constexpr std::size_t size = std::tuple_size<std::decay_t<Tuple>>::value;
    static_assert(size > 0, "Cannot pop from an empty tuple!");
    
    return details::index_apply<size-1>([&](auto... Is) {
        return std::make_tuple(std::get<Is>(std::forward<Tuple>(t))...);
    });
}
 
} // namespace stdext