Programming and Graphics

6.8 Algebra on real numbers 169

void algebra::print() const

{

cout << x <<""<<color << endl;

}

//---

void algebra::shift(double y)

{

color = setcolor(x+y);

x = x+y;

}

Following is a main program that uses the algebra class:

int main()

{

string chroma;

algebra A = algebra();

A.print();

cout << A.get(chroma) << " " << chroma << endl;

algebra B = algebra(-0.9);

B.print();

B.shift(2.1);

B.print();

return 0;

}

Running this program produces on the screen:

0 white

0 white

-0.9 red

1.2 black

Two features are worth emphasizing:

• Thegetfunction returns the value ofxthrough the functionreturn
  and passes the color through an argument endowed with the reference
  declarator (&).


• Because the functionsetcolorhas been declared private, it cannot be
  called from the main program.