# smiley and frowny, derived classes [fltk]

Bjarne Stroustrup “Programming Principles and Practice Using C++”
Chapter 14 Exercise 1
Using GUI library called FLTK (Fast Light Tool Kit, “full tick”).

```Output:

```

[code language=”cpp”]
// Philipp Siedler
// Bjarne Stroustrup’s PP
// Chapter 14 Exercise 1

#define _USE_MATH_DEFINES
#include "Simple_window.h"
#include "Graph.h"
#include <cmath>
using namespace Graph_lib;

class MyArc : public Shape
{
Point center;
float start;
float end;

public:
MyArc(Point c, double r, double s, double e)
: center(c)
, start(s)
, end(e)
{
};

void draw_lines() const;
};

void MyArc::draw_lines() const
{
int h = w;
if (color().visibility()) {
fl_arc(point(0).x, point(0).y, w, h, start, end);
}
}

Point& operator+(Point& a, Point& b) {
return Point(a.x + b.x, a.y + b.y);
}

class Face : public Circle
{
public:
void draw_lines() const;
void set_color(Color color);
protected:
{
set_color(Color::visible);
};
private:
Circle left_eye;
Circle right_eye;
};

void Face::draw_lines() const
{
Circle::draw_lines();
left_eye.draw();
right_eye.draw();
}

void Face::set_color(Color color)
{
Shape::set_color(color);
left_eye.set_color(color);
right_eye.set_color(color);
}

class Smiley : public Face
{
public:
{ };
void draw_lines() const;

private:
MyArc mouth;
};

void Smiley::draw_lines() const
{
Face::draw_lines();
mouth.draw_lines();
}

class Frowny : public Face
{
public:
{ };
void draw_lines() const;

private:
MyArc mouth;
};

void Frowny::draw_lines() const
{
Face::draw_lines();
mouth.draw_lines();
}

class Smiley_hat : public Smiley
{
public:
pt3(Point(center.x, center.y – radius * 1.5)),
ln1(pt1, pt3),
ln2(pt3, pt2)
{
ln1.set_color(Color::black);
ln2.set_color(Color::black);
};

void draw_lines() const;
Point point_on_circle(Circle& circle, double paramter);
private:
Point pt1;
Point pt2;
Point pt3;
Line ln1;
Line ln2;
};

Point Smiley_hat::point_on_circle(Circle& circle, double paramter) {
return Point(circle.radius() * cos(M_PI * 2 * paramter) + circle.center().x, circle.radius() * sin(M_PI * 2 * paramter) + circle.center().y);
}

void Smiley_hat::draw_lines() const
{
Smiley::draw_lines();
ln1.draw();
ln2.draw();
}

int main()
try
{
Point tl(100, 100);
Simple_window win(tl, 720, 400, "Simple Window");
Point center(win.x_max() / 2, win.y_max() / 2);

Smiley_hat smiley(Point(center.x – 100, center.y), 80);
Frowny frowny(Point(center.x + 100, center.y), 80);

win.attach(smiley);
win.attach(frowny);

win.wait_for_button();
}
catch (exception& e) {
cout << e.what() << endl;
return 1;
}
catch (…) {
cout << "Exiting" << endl;
return 2;
}
[/code]