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// function::target example
#include <iostream> // std::cout, std::boolalpha
#include <functional> // std::function, std::plus, std::minus
int my_plus (int a, int b) {return a+b;}
int my_minus (int a, int b) {return a-b;}
int main () {
std::function<int(int,int)> foo = my_plus;
std::function<int(int,int)> bar = std::plus<int>();
// calling using functional form:
std::cout << foo(100,20) << '\n';
std::cout << bar(100,20) << '\n';
// calling by invoking target:
std::cout << (*foo.target<int(*)(int,int)>())(100,20) << '\n';
std::cout << (*bar.target<std::plus<int>>())(100,20) << '\n';
// changing target directly:
*foo.target<int(*)(int,int)>() = &my_minus;
std::cout << foo(100,20) << '\n';
return 0;
}
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