demo1.dart~

#!dart
import 'dart:math';

class Point{
  num x;
  num y;
  Point(num x, num y){
    this.x = x;
    this.y = y;
  }
  num distance( Point p2){
      num dx = this.x - p2.x;
      num dy = this.y - p2.y;
      num distance = sqrt(dx*dx+dy*dy);
      return distance;
  }
}

class Rec {
  num x;
  num y;
  Rec(this.x, this.y);

  num area(){
    return x*y;
  }

}

class Square extends Rec {
  Square(num x): super(x, x);
}

num x(Rec y) {
  return y.x;
}



void main(){
  Point p1 = new Point(322,8);
  Point p2 = new Point(8,1);  
  print("${p1.x} \t${p1.y}");
  print("${p2.x} \t${p2.y}");
  num dis = p1.distance(p2);
  bool test = p1 == p2;
  print("$test");
  print("$dis");
  Square s = new Square(2);
  print("${x(s)}");

}