std::apply

 

C++

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optional

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in_placein_place_typein_place_indexin_place_tin_place_type_tin_place_index_t

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Defined in header <tuple>
template <class F, class Tuple> constexpr decltype(auto) apply(F&& f, Tuple&& t);		(since C++17)

Invoke the Callable object f with a tuple of arguments.

Parameters

f	-	Callable object to be invoked
t	-	tuple whose elements to be used as arguments to f

Return value

What returned by f.

Notes

The tuple need not be std::tuple, and instead may be anything that supports std::get and std::tuple_size; in particular, std::array and std::pair may be used.

Possible implementation

namespace detail { template <class F, class Tuple, std::size_t... I> constexpr decltype(auto) apply_impl(F &&f, Tuple &&t, std::index_sequence<I...>) { return std::invoke(std::forward<F>(f), std::get<I>(std::forward<Tuple>(t))...); } } // namespace detail   template <class F, class Tuple> constexpr decltype(auto) apply(F &&f, Tuple &&t) { return detail::apply_impl( std::forward<F>(f), std::forward<Tuple>(t), std::make_index_sequence<std::tuple_size_v<std::decay_t<Tuple>>>{}); }