class Edge {
  color c = 0;
  Node n0, n1;
  float dx, dy;
  Edge(Node n0, Node n1) {
    this.n0 = n0;
    this.n1 = n1;
    n0.edges.add(this);
    n1.edges.add(this);
  }
  void paint(){
    stroke(c);
    line(n0.x, n0.y, n1.x, n1.y);
  }
  float len() {
    return sqrt(sq(n0.x-n1.x)+sq(n0.y-n1.y));
  }
  float dx() {
    return n1.x-n0.x;
  }
  float dy() {
    return n1.y-n0.y;
  }
}