Programming and Graphics

6.11 The class of points in a plane 177

• Setbequal to theycoordinate of pointA:

doubleb=A.gety();

• Print the coordinates of pointA:

cout<<A.getx()<<""<<A.gety()<<endl;

Note that the main function is not able to access directly the private
variablesxandy, and must rely on member functions to fetch them.

We can directly add two points A and B by overloading the + operator.
This is done by inserting the following declaration in the public section of the
class:

point operator + (point);

and defining the algebra class addition function:

point point::operator + (point B)

{

point add;

add.x=x+B.x;

add.y=y+B.y;

return add;

}

Once this is done, we can state in the main program:

point C;

C=A+B;

We can refer to the class members by pointers, as discussed in Section
6.10. Thus, if A and Z are defined members, including in the main code the
statements:

point * pntname;

pntname = &A;

cout<<pntname<<endl;

point Z = *pntname;

Z.print();

pntname->print();

prints on the screen:

0xbfed5168

0.3 0.4

0.3 0.4