// Import the dart: math module to access the "sqrt" function.
import 'dart:math' as math;

// Definition of the Point class.
class Point {

    // The keyword "final" means that variables can only be assigned once.
    final num x, y;

    // A constructor: the syntactic sugar allows to initialize the variables.
    Point(this.x, this.y);

    // A named constructor, with an initialization list.
    Point.origin() : x = 0, y = 0;

    // Definition of a method.
    num distanceTo(Point other) {
        var dx = x - other.x;
        var dy = y - other.y;
        return math.sqrt(dx * dx + dy * dy);
    }
}

// main() is the entry point for Dart programs.
main() {
    // Instantiation of Point objects.
    var p1 = new Point(10, 10);
    var p2 = new Point.origin();
    var distance = p1.distanceTo(p2);
    print(distance);
}