< cpp‎ | utility
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.


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

Return value

What returned by f.


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),


#include <iostream>
#include <tuple>
int add(int first, int second)
    return first + second;    
template<typename T>
T add_generic(T first, T second)
    return first + second;    
int main()
    std::cout << std::apply(add, std::make_tuple(1,2)) << '\n';
    // template argument deduction/substitution fails
    // std::cout << std::apply(add_generic, std::make_tuple(2.0f,3.0f)) << '\n'; 



See also

creates a tuple object of the type defined by the argument types
(function template)
creates a tuple of rvalue references
(function template)
Construct an object with a tuple of arguments
(function template)
invokes any Callable object with given arguments
(function template)