????------------------------------?????????1????????2????-----------------------------------------
????extern B f();
????const A& rca2 = f();// f()?????????????????rvalue??
????// the cv1 >= cv2: const > ??????η???2.1???????
????struct X {
????operator B();
????operator int&();
????} x;
????const A& r = x;// x ?????????
????// r ??x ????reference-compatible??
????// x ???operator B()??????????????prvalue?? tmpB
????// r ??tmpB ????????2.1????????2.2???????
????-----------------------?????????1????????????2????????3????---------------------------
????const double& rcd2 = 2; // 2?????????lvalue/xvalue/???????prvalue/?????????????????
????// ??????????????2.0??3???????
????--------?????????1????????????2????????????3????????4????----------------------
????double d2 = 1.0;
????double&& rrd2 = d2; // rrd2?????rvalue reference?????????lvalue ?????4???????
????-----------------------------------------?????Щ????-------------------------------------------------------------
????const volatile int cvi = 1;
????const int& r2 = cvi; // error?? in this example?? the cv1 <= cv2?? which violate the 1.1
????*************************????????????*************************
????class Dog
????{
????public:
????Dog(){}
????virtual ~Dog(){}
????};
????void NonConstReference (Dog & dog )
????{
????//tell the dog to do something here
????}
????void TestNonConstReference ()
????{
????NonConstReference( Dog());
????}
????NonConstReference( Dog())?????????????????????????prvalue??
????????ISO??????????????1?????????????2?????????
????????2???NonConstReference(Dog & dog )?е?Dog & dog ??????const Dog & dog??
??????????????????????????
????************************??????????????????????????*****************************
??????????????????????c++??????????????????飺
????????????lvalue reference?? ?????????????rvalue.
??????????????ó?const lvalue reference.
???????????????????const???????c++??????????????????????????????????????????????????
????????????????????????????const???ò?????????????????л????????????????????????????????????????ú?????????
???????c++????????????????????????????const??????????????????????????????????÷?????????