public class Test3 {

  public static class Position2D {
    public double x = 0.0;
    public double y = 0.0;
  };

  public static class Polygone2D {
    public int n = 0;
    public Position2D [] tp = null;
  };
  
  public static void affichage(Position2D p) {
    Ecran.afficher(p.x," ",p.y);
  }
  
  public static void affichage(Polygone2D p) {
    Ecran.afficherln("Nombre de sommets : ",p.n);
    Ecran.afficherln("Liste des sommets : ");
    for ( int i = 0 ; i < p.n ; i++ ) {
      affichage(p.tp[i]);
      Ecran.sautDeLigne();
    }
  }
  
  public static Position2D [] creationTableauPosition2D(int n) {
    Position2D [] t = new Position2D[n];
    for ( int i = 0 ; i < n ; i++ ) {
      t[i] = new Position2D();
    }
    return t;
  }
  
  public static Polygone2D creationPolygone(int n) {
    Polygone2D p = new Polygone2D();
    p.n = n;
    p.tp = creationTableauPosition2D(n);
    return p;
  }
  
  public static Polygone2D creationPolygoneRegulier(int n,double r) {
    Polygone2D p = creationPolygone(n);
    for ( int i = 0 ; i < n ; i++ ) {
      double angle = i*Math.PI*2.0/n;
      p.tp[i].x = r*Math.cos(angle);
      p.tp[i].y = r*Math.sin(angle);
    }
    return p;
  }
  
  public static double distance(Position2D p1,Position2D p2) {
    double dx = p2.x - p1.x;
    double dy = p2.y - p1.y;
    return Math.sqrt(dx*dx+dy*dy);
  }
  
  public static double perimetre(Polygone2D p) {
    double per = 0.0;
    if ( p.n >= 2 ) {
      per = distance(p.tp[p.n-1],p.tp[0]);
      for ( int i = 0 ; i < p.n-1 ; i++ ) {
        per += distance(p.tp[i],p.tp[i+1]);
      }
    }
    return per;
  }
  
  /**
    * Fonction principale
    * @param args Les arguments.
    *
    */
  public static void main(String [] args) {
    Polygone2D p = creationPolygoneRegulier(7,2.0);
    affichage(p);
    Ecran.afficherln("Perimetre : ",perimetre(p));
  }
}