C++11 右值引用容易疏忽的两个点

#include 
#include 
 
void f(int& x) {
    std::cout << "lvalue reference overload f(" << x << ")n";
}
 
void f(const int& x) {
    std::cout << "lvalue reference to const overload f(" << x << ")n";
}
 
void f(int&& x) {
    std::cout << "rvalue reference overload f(" << x << ")n";
}
 
int main() {
    int i = 1;
    const int ci = 2;
    f(i);  // calls f(int&)
    f(ci); // calls f(const int&)
    f(3);  // calls f(int&&)
           // would call f(const int&) if f(int&&) overload wasn't provided
    f(std::move(i)); // calls f(int&&)
 
    // rvalue reference variables are lvalues when used in expressions
    int&& x = 1;
    f(x);            // calls f(int& x)
    f(std::move(x)); // calls f(int&& x)
}

	Rule& addElement(Element&& element)
	{
		// element在使用的时候会自动变成左值，需要用std::move强制转换右值
		ruleElements.push_back(std::move(element));
		return *this;
	}

	Element(Element&& r) noexcept
	{
		*this = r;
		printf("Element(Element&& r)n");
	}