Inside The C++ Object Model ---- Object Lessons

1. Layout Cost for Adding Encapsulation
inheritance don't have cost. But virtual function and virtual base class will add extra cost.

2. C++ Object Model
How Compiler implement the OO:
A Simple Object Model
A Table-driven Object Model
Two conceptions: virtual table vtbl;
vptr

How the Object Model Effects Programs
X foobar(){
    X xx;
    X *px = new X;

    //foo() is virtual fucntion
    xx.foo();
    px->foo();
    delete px;
    return xx;
};

3.  A Keyword Distinction
template <struct Type>
template <class Type>
struct mumble { ... };

4.  An Object Distinction
C++ 直接支持三种programming paradigms (what's paradigm)
1.procedural model
2.abstract data type model
 String girl = "Anna"
 String daughter;
 daughter = girl;
 if (daughter == girl){
  ...
 }

3.object-oriented model
 void check_in(Library_materials *pmat){
  if (pmat->late())
   pmat->check_in();
  if (Lender *plend = pmat->reserved())
   pmat->notify( plend );
 }

PROBLEM:

Book book;
thing1=book;
//book is sliced
think.check_in();

Library_materials &thing2 = book;
thing.check_in();

think1 = book 是ADT paradigm 的一种行为，用于OO就乱了
Although the polymorphic manipulation of an object requires that the object be accessed either through a
pointer or a reference, the manipulation of a pointer or reference in C++ does not in itself necessarily result
in polymorphism!

The C++ language supports polymorphism in the following ways:
1. Through a set of implicit conversions, such as the conversion of a derived class pointer to a pointer of
its public base type:
 shape *ps = new circle();
2. Through the virtual function mechanism:
 ps->rotate();
3. Through the dynamic_cast and typeid operators:
 if ( circle *pc =
  dynamic_cast< circle* >( ps )) ...