// inherit10.cpp       		By: Aiman Hanna -  ©1993-2002 Aiman Hanna

// This program explains what "pure" virtual functions are, and how can we
// use pure virtual functions to disallow creation of objects from a base 
// class. [ In such a case, the base class is called "abstract" base class.
// Note that this program does not work. Why?
// Key points:  1) Pure virtual functions.
// 		2) Abstract base classes.

#include "inherit10.h"

// Definition of Vehicle's member functions

Vehicle::Vehicle( void )
{
 cout << "\n Vehicle...Executing the default constructor of the Vehicle class. "  << "\n";
	color = green;	     
	numcyl = 4;	    
}




Vehicle::Vehicle( avl_colors clr, int cyl )
{      
 cout << "\n Vehicle...Executing the parameterized constructor of the Vehicle class." << "\n";
	color = clr;	     
	numcyl = cyl;	    

} 



void Vehicle::ShowInfo( void )
{
	// Is the following information enough?
	cout << " Vehicle....Here is all the known information: " << "\n";	
	cout << " The vehicle color is: " << GetColor( ) << ",\n";
	cout << " and the number of cylinders is: " << GetNumCyl( )  << "\n\n\n";

}



int Vehicle::GetNumCyl( void )
{
 return numcyl;
}



char* Vehicle::GetColor( void )
{
 switch ( color )
 {
  case red:    return "red";  
  case black:  return "black";
  case white:  return "white";
  case green:  return "green";
 }
return "unknown";
}




// Define Bus's member functions

Bus::Bus( avl_colors aclr, int cyl, yes_no bar ) : Vehicle( aclr, cyl )
{
 cout << " Bus...Executing the constructor of the bus class. " << "\n";

 barexist = bar;
}



void Bus::ShowInfo( void )
{
  // Bus had to redefine this function from the base clas
  // to include its specific information

 cout << " Bus...Here is all the needed information: " << "\n";
 cout << " The bus color is: " << GetColor( ) << ",\n";
 cout << " the number of cylinders is: " << GetNumCyl( )  << ",\n";

 if ( HasBar( ) == yes )
        cout << " and the bus has a bar. " << "\n\n\n";
 else
        cout << " and the bus does not have a bar. " << "\n\n\n";
}



yes_no Bus::HasBar ( void )
{
 return barexist;
}




// Define Van's member functions

Van::Van( avl_colors aclr, int cyl, yes_no tur ) : Bus( aclr, cyl, no )
                                                                // always no bar
{
 cout << " Van...Executing the constructor of the Van class. " << "\n\n\n";
 turbo = tur;
}




void Van::ShowInfo( void )
{
 // Van had to redefine this function from the base clas
 // to include its specific information

 cout << " Van...Here is all the needed information: " << "\n";
 cout << " The van color is: " << GetColor( ) << ",\n";
 cout << " the number of cylinders is: " << GetNumCyl( )  << ",\n";

 if ( IsTurbo( ) == yes )
        cout << " and the van is turbo " << "\n\n\n";
 else
        cout << " and the van is not turbo. " << "\n\n\n";
}



yes_no Van::IsTurbo( void )
{
return turbo;
}




int main( void )
{

// Make use of virtual functions..
// Step #1 : create an array of 'pointers' to Vehicle class

Vehicle *Vec_arr[4];

// Step #2 : create the individual, derived objects.
// Notice that you can declare objects from Vehicle class. However, Does this 
// make sense? Why?

Vehicle vec1( red, 4 );		// This is the line where the compilation stops.
Bus     bs1( white, 12, yes );
Van     vn1( black, 8, yes );
Van     vn2( white, 6, no );

// Step #3 : put the addresses of these derived objects into our array

Vec_arr[0] = &vec1;
Vec_arr[1] = &bs1;
Vec_arr[2] = &vn1; 
Vec_arr[3] = &vn2;

			
// Step #4 : Execute all ShowInfo() of the objects by iterating 
// through the array.
			
for ( int counter = 0; counter < 4; counter++ )
	Vec_arr[ counter ] -> ShowInfo( ); 

// Step 5. See vehicle4.h

return 0;
}


// The result of compiling the program is as follow:
// On VC++
/*
Compiling...
inherit10.cpp
inherit10.cpp(152) : error C2259: 'Vehicle' : cannot instantiate abstract class due to following members:
inherit10.h(14) : see declaration of 'Vehicle'
inherit10.cpp(152) : warning C4259: 'void __thiscall Vehicle::ShowInfo(void)' : pure virtual function was not defined
inherit10.h(20) : see declaration of 'ShowInfo'
inherit10.cpp(152) : error C2259: 'Vehicle' : cannot instantiate abstract class due to following members:
inherit10.h(14) : see declaration of 'Vehicle'
inherit10.cpp(152) : warning C4259: 'void __thiscall Vehicle::ShowInfo(void)' : pure virtual function was not defined
inherit10.h(20) : see declaration of 'ShowInfo'
*/


// On UNIX
/*
CC: "inherit10.cpp", line 152: error: declaration of object of abstract class Vehicle - pure virtual
function(s) have not been defined (1570)
*/