struct tuple_element<__i, tuple<>>
{
static_assert(__i < tuple_size<tuple<>>::value,
- "tuple index is in range");
+ "tuple index must be in range");
};
template<size_t __i, typename _Head, typename... _Tail>
__get_helper(const _Tuple_impl<__i, _Head, _Tail...>& __t) noexcept
{ return _Tuple_impl<__i, _Head, _Tail...>::_M_head(__t); }
+ // Deleted overload to improve diagnostics for invalid indices
+ template<size_t __i, typename... _Types>
+ __enable_if_t<(__i >= sizeof...(_Types))>
+ __get_helper(const tuple<_Types...>&) = delete;
+
/// Return a reference to the ith element of a tuple.
template<size_t __i, typename... _Elements>
constexpr __tuple_element_t<__i, tuple<_Elements...>>&
get(tuple<_Elements...>&& __t) noexcept
{
typedef __tuple_element_t<__i, tuple<_Elements...>> __element_type;
- return std::forward<__element_type&&>(std::get<__i>(__t));
+ return std::forward<__element_type>(std::__get_helper<__i>(__t));
}
/// Return a const rvalue reference to the ith element of a const tuple rvalue.
get(const tuple<_Elements...>&& __t) noexcept
{
typedef __tuple_element_t<__i, tuple<_Elements...>> __element_type;
- return std::forward<const __element_type&&>(std::get<__i>(__t));
+ return std::forward<const __element_type>(std::__get_helper<__i>(__t));
}
#if __cplusplus >= 201402L
#define __cpp_lib_tuples_by_type 201304
- template<typename _Head, size_t __i, typename... _Tail>
- constexpr _Head&
- __get_helper2(_Tuple_impl<__i, _Head, _Tail...>& __t) noexcept
- { return _Tuple_impl<__i, _Head, _Tail...>::_M_head(__t); }
-
- template<typename _Head, size_t __i, typename... _Tail>
- constexpr const _Head&
- __get_helper2(const _Tuple_impl<__i, _Head, _Tail...>& __t) noexcept
- { return _Tuple_impl<__i, _Head, _Tail...>::_M_head(__t); }
+ // Return the index of _Tp in _Types, if it occurs exactly once.
+ // Otherwise, return sizeof...(_Types).
+ // TODO reuse this for __detail::__variant::__exactly_once.
+ template<typename _Tp, typename... _Types>
+ constexpr size_t
+ __find_uniq_type_in_pack()
+ {
+ constexpr size_t __sz = sizeof...(_Types);
+ constexpr bool __found[__sz] = { __is_same(_Tp, _Types) ... };
+ size_t __n = __sz;
+ for (size_t __i = 0; __i < __sz; ++__i)
+ {
+ if (__found[__i])
+ {
+ if (__n < __sz) // more than one _Tp found
+ return __sz;
+ __n = __i;
+ }
+ }
+ return __n;
+ }
/// Return a reference to the unique element of type _Tp of a tuple.
template <typename _Tp, typename... _Types>
constexpr _Tp&
get(tuple<_Types...>& __t) noexcept
- { return std::__get_helper2<_Tp>(__t); }
+ {
+ constexpr size_t __idx = __find_uniq_type_in_pack<_Tp, _Types...>();
+ static_assert(__idx < sizeof...(_Types),
+ "the type T in std::get<T> must occur exactly once in the tuple");
+ return std::__get_helper<__idx>(__t);
+ }
/// Return a reference to the unique element of type _Tp of a tuple rvalue.
template <typename _Tp, typename... _Types>
constexpr _Tp&&
get(tuple<_Types...>&& __t) noexcept
- { return std::forward<_Tp&&>(std::__get_helper2<_Tp>(__t)); }
+ {
+ constexpr size_t __idx = __find_uniq_type_in_pack<_Tp, _Types...>();
+ static_assert(__idx < sizeof...(_Types),
+ "the type T in std::get<T> must occur exactly once in the tuple");
+ return std::forward<_Tp>(std::__get_helper<__idx>(__t));
+ }
/// Return a const reference to the unique element of type _Tp of a tuple.
template <typename _Tp, typename... _Types>
constexpr const _Tp&
get(const tuple<_Types...>& __t) noexcept
- { return std::__get_helper2<_Tp>(__t); }
+ {
+ constexpr size_t __idx = __find_uniq_type_in_pack<_Tp, _Types...>();
+ static_assert(__idx < sizeof...(_Types),
+ "the type T in std::get<T> must occur exactly once in the tuple");
+ return std::__get_helper<__idx>(__t);
+ }
/// Return a const reference to the unique element of type _Tp of
/// a const tuple rvalue.
template <typename _Tp, typename... _Types>
constexpr const _Tp&&
get(const tuple<_Types...>&& __t) noexcept
- { return std::forward<const _Tp&&>(std::__get_helper2<_Tp>(__t)); }
+ {
+ constexpr size_t __idx = __find_uniq_type_in_pack<_Tp, _Types...>();
+ static_assert(__idx < sizeof...(_Types),
+ "the type T in std::get<T> must occur exactly once in the tuple");
+ return std::forward<const _Tp>(std::__get_helper<__idx>(__t));
+ }
#endif
// This class performs the comparison operations on tuples