code.cpp

function<int(int)> g(function<int(int)> f){
	cout << " exec g !\n";
	return [f](int x) -> int {
		cout<< " exec g return lambda! "<< x << endl;
		return f(x + 1);
	};
}

void e(function<int(int)> F){
	cout<< " exec e !\n";
	F(1);
}
void sandbox(){
	cout << "(1)\n";
	auto F1 =
		g(
			g([](int x){
				cout <<" exec g argv lambda! "<< x << endl;
				return x + 1;
			})
		);
	auto F2 = [F1](int x){
		cout << " exec F2 lambda! "<< x << endl;
		return F1(x);
	};
	cout << "(2)\n";
	e(F2);
	auto F3 = [f = F2(5)](int x){
		cout << " exec F3 lambda! "<< x << endl;
		return f;			
	};
	cout << "(3)\n";
	e(F3);
}

result

(1)
 exec g !
 exec g !
(2)
 exec e !
 exec F2 lambda! 1
 exec g return lambda! 1
 exec g return lambda! 2
 exec g argv lambda! 3
 exec F2 lambda! 5
 exec g return lambda! 5
 exec g return lambda! 6
 exec g argv lambda! 7
(3)
 exec e !
 exec F3 lambda! 1