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#include <iostream>
 
void g(int && v1, int & v2)
{
    std::cout << v1 << " " << ++v2 << std::endl;
}
 
template <typename F, typename T1, typename T2>
void flip(F f,T1 && t1, T2  && t2){
    g(t2, t1);
}
 
int main() {
	int i = 1, j = 1;
 
    g(12, i); // f changes i
	std::cout << "i = " << i << ", j = " << j << std::endl;
 
	flip(g, j, 2);
	std::cout << "i = " << i << ", j = " << j << std::endl;
 
	return 0;
}

prog.cpp: In instantiation of 'void flip(F, T1&&, T2&&) [with F = void (*)(int&&, int&); T1 = int&; T2 = int]':
prog.cpp:19:14:   required from here
prog.cpp:10:13: error: cannot bind 'int' lvalue to 'int&&'
     g(t2, t1);
             ^
prog.cpp:3:6: note: initializing argument 1 of 'void g(int&&, int&)'
 void g(int && v1, int & v2)
      ^

Standard output is empty