20 General utilities library [utilities]

20.5 Tuples [tuple]

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

template<class F, class Tuple> constexpr decltype(auto) apply(F&& f, Tuple&& t);
Effects: Given the exposition-only function: template<class F, class Tuple, size_t... I> constexpr decltype(auto) apply-impl(F&& f, Tuple&& t, index_sequence<I...>) { // exposition only return INVOKE(std::forward<F>(f), std::get<I>(std::forward<Tuple>(t))...); // see [func.require] }
Equivalent to: return apply-impl(std::forward<F>(f), std::forward<Tuple>(t), make_index_sequence<tuple_size_v<remove_reference_t<Tuple>>>{});
template<class T, class Tuple> constexpr T make_from_tuple(Tuple&& t);
Effects: Given the exposition-only function: template<class T, class Tuple, size_t... I> requires is_constructible_v<T, decltype(get<I>(declval<Tuple>()))...> constexpr T make-from-tuple-impl(Tuple&& t, index_sequence<I...>) { // exposition only return T(get<I>(std::forward<Tuple>(t))...); }
Equivalent to: return make-from-tuple-impl<T>( std::forward<Tuple>(t), make_index_sequence<tuple_size_v<remove_reference_t<Tuple>>>{});
[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]