C++ Overview

1. // Comment style is standard
-------------------------------

  As mentioned, also adopted for C99.

2. void in parameter list is optional
-------------------------------------

  int fn(void);

  int fn();

  I prefer to use void, but in C++, it is a matter of personal preference.

3. default arguments
--------------------

  int fn(int n=1)
  {

  }

  fn can now be called two different ways:

  fn(4);   sets fn's n variable to 4

  fn();    sets fn's n variable to the default of 2

4. reference arguments
----------------------

  References are a different way of handling pointers.

  void fn(int& a)
  {
     a=4;
  }

  Now if we call:

  int y=1;
  fn(y);

  Inside fn, we change the value of y just as if it had been passed as a
  pointer value.

5. Function overloading
-----------------------

  Multiple functions with similar actions can be called the same thing:

  float area(float h, float w)
  {
    return(h*w);
  }

  int area(int h, int w)
  {
    return(h*w);
  }

  The compiler decides which to call based on the parameters.

6. Function templates
---------------------

  template <class T> T area(T h, T w)
  {
    return(h*w);
  }

  int area(int,int);
  float area(float, float);

  The function is exactly the same for both types, int and float, so C++ allows
  a template to be created.  The individual functions are creates based on the
  prototypes.

7. global scope resolution
--------------------------

  int a;

  int fn(int a)
  {
    return(a * ::a);
  }

  The :: in front of the global variable name allows access to the global while
  the local is still accessible.

8. Classes
----------

  Classes are the reason that C++ was created - allows collections of objects
  and methods (variables and functions) that are related.


  class Rectangle {
    Rectangle(int, int);
    void print();
    int area();
    int getH();
    int getW();
    void setH(int);
    void setW(int);

    private:
      int h;
      int w;
  };

  This creates the class with several methods and two properties (h and w).

  Rectangle r;       // creates a new rectangle object
  r.setH(10);
  r.setW(10);
  r.print();         // "w=1-, h=10"
  area = r.area();   // returns 100
  r.h = 10;          // illegal
  r.w = 10;          // illegal

  Rectangle::Rectangle(int a=0; b=0)     // constructor
  {
    h = a;                               // set private h to a
    w = b;                               // set private w to b
  }

  void Rectangle::print()
  {
    cout << "w=" << w << " h=" << h << endl;
    return;
  }


  C++ has all of the features of C, plus classes and associated technology
  enhancements:

    encapsulation (classes, public, private)
    inheritance (using a class to create a new class)
    polymorphism (changing code based on context - templates and overloading)