std::experimental::apply
From cppreference.com
< cpp | experimental
| Defined in header <experimental/tuple>
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||
| template< class F, class Tuple > constexpr decltype(auto) apply(F&& f, Tuple&& t); |
(library fundamentals TS) | |
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.
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))...); // Note: std::invoke is a C++17 feature } } // 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>>>{}); } |
Example
Run this code
#include <iostream> #include <tuple> template<typename... Ts> void print_tuple(const std::tuple<Ts...> &tuple) { std::apply([](const auto&... elem) { ((std::cout << elem << '\n'), ...); }, tuple); } int main() { const std::tuple<int, char> t = std::make_tuple(5, 'a'); print_tuple(t); }
Output:
5 a
See also
| (C++11) |
creates a tuple object of the type defined by the argument types (function template) |
| (C++11) |
creates a tuple of forwarding references (function template) |