5. const A& B::blah (const C& c) const {...}
Passed in a reference to a constant object ‘c’
 ‘c’ cannot be modified in the function
const A& B::blah (const C& c) const {...}
Return a reference to a constant object
 The returned object can then only call constant methods
This is a constant method, meaning this object is treated as a constant during this function
 None of its data members can be modified

6. Making “friends” between classes
When a data member is declared “private”, all the other classes cannot access it directly
 Must call through “member functions”
Unless, declare myself (MyClass) as “friend” of other class (OtherClass)
class MyClass {
friend class OtherClass;
... };
 OtherClass can access MyClass’s data members
OtherClass::f() {
...; myClassObj._myClassData; ... }
 Not recommended (unless no better way)

7. Common usage of friend class
If some class A is designed specifically for another certain class B, and is intended to hide from others...
 Making A a friend class to B
For example,
class ListNode {
friend class List;
... };
class List
ListNode* _head;
T& front() { return *(_head); }

8. Friend of a Member Function
Instead of making MyClass as friend to the whole OtherClass, however, we can make friend with only certain member functions in OtherClass
e.g.
class MyClass {
friend void OtherClass::setData
(const MyClass&);
int _db;
... };
void OtherClass::setData(const MyClass& b) {
_da = b._db; }
(See also) Operator overload
* .../refSrc/lec03/friend1.cpp

13. Pay attention to the function prototypes below...
T& operator = (const T& v);
T& operator [] (size_type i);
const T& operator [] (size_type i) const;
T operator ~ () const; // also for -, &, |, etc
T& operator ++(); // ++v
T operator ++(int); // v++
T operator + (const T& v) const;
// also for -,*,&,etc
T& operator += (const T& v);
// also for -=,*=,&=,etc
bool operator == (const T& v) const;
//also for !=, etc
friend ostream& operator << (ostream&, const T&);
The operator ‘()’ can also be overloaded and used as “generator”

14. T& operator = (const T& v);

15. T& operator [] (size_type i)