Simple Class Declaration Example

//A canonical example of a class declaration and
//implementation is a complex number class.

//Here follows the class declaration.

class Complex { //begin declaration

public: //all public members follow

  Complex(double x, double y); //declaration of constructor
  ~Complex(); //declaration of destructor

  //put here accessor functions 

  double Re();
  double Im();
  double Mod();

  //put here operations

protected: //all protected members follow, perhaps none

private: //all private members follow, state data members 

  double _x; //real component
  double _y; //imaginary component

  //alternatively
  // double _r; //radius
  // double _theta; //argument
  //by making the state data members private the         
  //implementor is free to change between these two 
  //implementation of a complex number without affecting
  //the public member function declarations.

}; //end declaration with curly brace and semicolon

//The member function definitions might look something 
//like this:

Complex::Complex(double re, double im) { //begin definition of constructor
   _x=re;
   _y=im;
}

Complex::~Complex(){
  //does nothing
}

double Complex::Re(){
   return _x;
}

double Complex::Im(){
   return _y;
}

double Complex::Mod(){
  double z;
  z = sqrt(x*x + y*y); //sqrt in math library
}

etc.... 

Last modification: 11 Mar 2001
Last significant update: ?1999