Annex D (normative) Compatibility features [depr]

D.14 Tuple [depr.tuple]

The header <tuple> ([tuple.syn]) has the following additions:

namespace std {
  template<class T> class tuple_size<volatile T>;
  template<class T> class tuple_size<const volatile T>;

  template<size_t I, class T> class tuple_element<I, volatile T>;
  template<size_t I, class T> class tuple_element<I, const volatile T>;
}

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template<class T> class tuple_size<volatile T>;
template<class T> class tuple_size<const volatile T>;

Let TS denote tuple_size<T> of the cv-unqualified type T.

If the expression TS::value is well-formed when treated as an unevaluated operand, then specializations of each of the two templates meet the Cpp17TransformationTrait requirements with a base characteristic of integral_constant<size_t, TS::value>.

Otherwise, they have no member value.

Access checking is performed as if in a context unrelated to TS and T.

Only the validity of the immediate context of the expression is considered.

In addition to being available via inclusion of the <tuple> ([tuple.syn]) header, the two templates are available when any of the headers <array> ([array.syn]), <ranges> ([ranges.syn]), or <utility> ([utility.syn]) are included.

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template<size_t I, class T> class tuple_element<I, volatile T>;
template<size_t I, class T> class tuple_element<I, const volatile T>;

Let TE denote tuple_element_t<I, T> of the cv-unqualified type T.

Then specializations of each of the two templates meet the Cpp17TransformationTrait requirements with a member typedef type that names the following type:

(4.1)
for the first specialization, add_volatile_t<TE>, and
(4.2)
for the second specialization, add_cv_t<TE>.