std::move_only_function:: operator()

Invokes the stored callable target with the parameters args . The /*cv*/ , /*ref*/ , and /*noex*/ parts of operator ( ) are identical to those of the template parameter of std::move_only_function .

Equivalent to return std:: invoke_r < R > ( /*cv-ref-cast*/ ( f ) , std:: forward < Args > ( args ) ... ) ; , where f is a cv-unqualified lvalue that denotes the target object of * this , and /*cv-ref-cast*/ ( f ) is equivalent to:

• f if cv ref is either empty or & , or
• std:: as_const ( f ) if cv ref is either const or const & , or
• std :: move ( f ) if cv ref is && , or
• std :: move ( std:: as_const ( f ) ) if cv ref is const && .

The behavior is undefined if * this is empty.

Parameters

Return value

std:: invoke_r < R > ( /*cv-ref-cast*/ ( f ) , std:: forward < Args > ( args ) ... ) .

Exceptions

Propagates the exception thrown by the underlying function call.

Example

#include <iostream>
#include <functional>
 
void call(std::move_only_function<int() const> f)  // can be passed by value
{ 
    std::cout << f() << '\n';
}
 
int normal_function() 
{
    return 42;
}
 
int main()
{
    int n = 1;
    auto lambda = [&n](){ return n; };
    std::move_only_function<int() const> f = lambda;
    call(std::move(f));
 
    n = 2;
    call(lambda); 
 
    f = normal_function; 
    call(std::move(f));
}

1
2
42

See also