universal reference

universal.cpp

template<typename T> void f(T&& param); // param is now a universal reference
int x = 27;
const int cx = x; 
const int& rx = x;
f(x);                                   // x is lvalue, so T is int&,
                                        // param's type is also int&
f(cx);                                  // cx is lvalue, so T is const int&,
                                        // param's type is also const int&
f(rx);                                  // rx is lvalue, so T is const int&,
                                        // param's type is also const int&
f(27);                                  // 27 is rvalue, so T is int,
                                        // param's type is therefore int&&