# linear function graphing 2/8 [fltk]

Bjarne Stroustrup “Programming Principles and Practice Using C++”
Chapter 15 Shape Graphing Drill 2
Using GUI library called FLTK (Fast Light Tool Kit, “full tick”).

```Output:

```

[code language=”cpp”]
// Philipp Siedler
// Bjarne Stroustrup’s PP
// Chapter 15 Shape Graphing Drill 2

#define _USE_MATH_DEFINES
#include "Simple_window.h"
#include "Graph.h"
#include <cmath>

using namespace Graph_lib;

constexpr int xmax = 600;
constexpr int ymax = 600;

constexpr int x_orig = xmax / 2;
constexpr int y_orig = ymax / 2;
Point orig(x_orig, y_orig);

constexpr int r_min = -10;
constexpr int r_max = 10;

constexpr int n_points = 400;

constexpr int x_scale = 20;
constexpr int y_scale = 20;

double one(double x)
{
return 1;
}

int main()
try
{
Point tl(100, 100);
Simple_window win(tl, xmax, ymax, "Function graphs.");

Axis x(Axis::x, Point(orig.x – 200, orig.y), 400, 20, "1 == 20");
x.set_color(Color::red);

Axis y(Axis::y, Point(orig.x, orig.y + 200), 400, 20, "1 == 20");
y.set_color(Color::red);

Function f1(one, r_min, r_max, orig, n_points, x_scale, y_scale);
f1.set_color(Color::black);

win.attach(f1);

win.attach(x);
win.attach(y);

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

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