cppdraft_translate/cppdraft/tuple/apply.md

[tuple.apply]

22 General utilities library [utilities]

22.4 Tuples [tuple]

22.4.6 Calling a function with a tuple of arguments [tuple.apply]

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template<class F, [tuple-like](tuple.like#concept:tuple-like "22.4.3 Concept tuple-like [tuple.like]") Tuple> constexpr apply_result_t<F, Tuple> apply(F&& f, Tuple&& t) noexcept(is_nothrow_applicable_v<F, Tuple>);

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Effects: Given the exposition-only function template:namespace std {template<class F, tuple-like Tuple, size_t... I>constexpr decltype(auto) apply-impl(F&& f, Tuple&& t, index_sequence<I...>) {// exposition onlyreturn INVOKE(std::forward(f), get(std::forward(t))...); // see [func.require]}}

Equivalent to:return apply-impl(std::forward(f), std::forward(t), make_index_sequence<tuple_size_v<remove_reference_t>>{});

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template<class T, [tuple-like](tuple.like#concept:tuple-like "22.4.3 Concept tuple-like [tuple.like]") Tuple> constexpr T make_from_tuple(Tuple&& t);

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Mandates: If tuple_size_v<remove_reference_t> is 1, thenreference_constructs_from_temporary_v<T, decltype(get<0>(declval()))> is false.

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Effects: Given the exposition-only function template:namespace std {template<class T, tuple-like Tuple, size_t... I>requires is_constructible_v<T, decltype(get(declval()))...>constexpr T make-from-tuple-impl(Tuple&& t, index_sequence<I...>) { // exposition onlyreturn T(get(std::forward(t))...); }}

Equivalent to:return make-from-tuple-impl( std::forward(t), make_index_sequence<tuple_size_v<remove_reference_t>>{});

[Note 1:

The type of T must be supplied as an explicit template parameter, as it cannot be deduced from the argument list.

— end note]