tuple.ipp

/* VecMem project, part of the ACTS project (R&D line)
 *
 * (c) 2023 CERN for the benefit of the ACTS project
 *
 * Mozilla Public License Version 2.0
 */
#pragma once
 
// System include(s).
#include <cstddef>
#include <type_traits>
 
namespace vecmem {
namespace details {
 
template <std::size_t I>
struct tuple_get_impl {
 
    template <typename... Ts>
    VECMEM_HOST_AND_DEVICE static constexpr const auto &get(
        const tuple<Ts...> &t) {
        return tuple_get_impl<I - 1>::get(t.m_tail);
    }
    template <typename... Ts>
    VECMEM_HOST_AND_DEVICE static constexpr auto &get(tuple<Ts...> &t) {
        return tuple_get_impl<I - 1>::get(t.m_tail);
    }
 
};  // struct tuple_get_impl
 
template <>
struct tuple_get_impl<0> {
 
    template <typename... Ts>
    VECMEM_HOST_AND_DEVICE static constexpr const auto &get(
        const tuple<Ts...> &t) {
        return t.m_head;
    }
    template <typename... Ts>
    VECMEM_HOST_AND_DEVICE static constexpr auto &get(tuple<Ts...> &t) {
        return t.m_head;
    }
 
};  // struct tuple_get_impl
 
}  // namespace details
 
template <std::size_t I, typename... Ts>
VECMEM_HOST_AND_DEVICE inline constexpr const auto &get(
    const tuple<Ts...> &t) noexcept {
 
    // Make sure that the requested index is valid.
    static_assert(I < sizeof...(Ts),
                  "Attempt to access index greater than tuple size.");
 
    // Return the correct element using the helper struct.
    return details::tuple_get_impl<I>::get(t);
}
 
template <std::size_t I, typename... Ts>
VECMEM_HOST_AND_DEVICE inline constexpr auto &get(tuple<Ts...> &t) noexcept {
 
    // Make sure that the requested index is valid.
    static_assert(I < sizeof...(Ts),
                  "Attempt to access index greater than tuple size.");
 
    // Return the correct element using the helper struct.
    return details::tuple_get_impl<I>::get(t);
}
 
template <typename... Ts>
VECMEM_HOST_AND_DEVICE inline constexpr tuple<Ts &...> tie(Ts &... args) {
 
    return tuple<Ts &...>(args...);
}
 
template <class... Ts>
VECMEM_HOST_AND_DEVICE inline constexpr tuple<typename std::decay<Ts>::type...>
make_tuple(Ts &&... args) {
    return tuple<typename std::decay<Ts>::type...>{std::forward<Ts>(args)...};
}
 
}  // namespace vecmem