(* Chapter 15 - Program 3 *)
program Inheritance_1;

{ ******************** class definitions **********************}

type
   Vehicle = object
      Wheels : integer;
      Weight : real;
      constructor Init(In_Wheels : integer; In_Weight : real);
      function Get_Wheels : integer;
      function Get_Weight : real;
      function Wheel_loading : real;
   end;


   Car = object(Vehicle)
      Passenger_Load : integer;
      constructor Init(In_Wheels : integer;
                       In_Weight : real;
                       People    : integer);
      function Passengers : integer;
   end;


   Truck = Object(Vehicle)
      Passenger_Load : integer;
      Payload        : real;
      constructor Init(People : integer;
                       Max_Load : real;
                       In_Wheels : integer;
                       In_Weight : real);
      function Efficiency : real;
      function Wheel_Loading :real;
   end;

{ ********************* class implementations ******************** }

   constructor Vehicle.Init(In_Wheels : integer; In_Weight : real);
   begin
      Wheels := In_Wheels;
      Weight := In_Weight;
   end;

   function Vehicle.Get_Wheels : integer;
   begin
      Get_Wheels := Wheels;
   end;

   function Vehicle.Get_Weight : real;
   begin
      Get_Weight := Weight;
   end;

   function Vehicle.Wheel_loading : real;
   begin
      Wheel_Loading := Weight/Wheels;
   end;

   constructor Car.Init(In_Wheels : integer;
                        In_Weight : real;
                        People    : integer);
   begin
      Wheels := In_Wheels;
      Weight := In_Weight;
      Passenger_Load := People;
   end;

   function Car.Passengers : integer;
   begin
      Passengers := Passenger_Load;
   end;

   constructor Truck.Init(People : integer;
                          Max_Load : real;
                          In_Wheels : integer;
                          In_Weight : real);
   begin
      Passenger_Load := People;
      Payload := Max_Load;
      Vehicle.Init(In_Wheels, In_Weight);
   end;

   function Truck.Efficiency : real;
   begin
      Efficiency := 100.0 * Payload / (Payload + Weight);
   end;

   function Truck.Wheel_Loading : real;
   begin
      Wheel_Loading := (Weight + Payload)/Wheels;
   end;

{ ************************ main program ************************** }

var Unicycle : Vehicle;
    Sedan    : Car;
    Semi     : Truck;

begin

   Unicycle.Init(1, 12.0);
   Sedan.Init(4, 2100.0, 5);
   Semi.Init(1, 25000.0, 18, 5000.0);

   WriteLn('The unicycle weighs ', Unicycle.Get_Weight:5:1,
           ' pounds, and has ', Unicycle.Get_Wheels, ' wheel.');

   WriteLn('The car weighs ', Sedan.Get_Weight:7:1,
           ' pounds, and carries ', Sedan.Passengers,
           ' passengers.');

   WriteLn('The semi has a wheel loading of ', Semi.Wheel_Loading:8:1,
           ' pounds per tire,');
   WriteLn(' and has an efficiency of ', Semi.Efficiency:5:1,
           ' percent.');

   with Semi do
   begin
      WriteLn('The semi has a wheel loading of ', Wheel_Loading:8:1,
              ' pounds per tire,');
      WriteLn(' and has an efficiency of ', Efficiency:5:1,
              ' percent.');
   end;
end.




{ Result of execution

The unicycle weighs  12.0 pounds, and has 1 wheel.
The car weighs  2100.0 pounds, and carries 5 passengers.
The semi has a wheel loading of   1666.7 pounds per tire,
 and has an efficiency of 83.3 percent.
The semi has a wheel loading of   1666.7 pounds per tire,
 and has an efficiency of 83.3 percent.

}