/* From: "COMPUTATIONAL PHYSICS, 2nd Ed" 
   by RH Landau, MJ Paez, and CC Bordeianu 
   Copyright Wiley-VCH, 2007.
   Electronic Materials copyright: R Landau, Oregon State Univ, 2007;
   MJ Paez, Univ Antioquia, 2007; and CC Bordeianu, Univ Bucharest, 2007.
   Support by National Science Foundation                              
*/
//  FERN.java:  statistical fern construction

import java.io.*;                          // Location of PrintWriter
import java.util.*;                             // Location of Random
import java.lang.*;                               // Location of Math

public class FERN  {
  
  public static void main(String[] argv) 
                      throws IOException, FileNotFoundException  {
    PrintWriter q = new PrintWriter(  // data file
       new FileOutputStream("FERN.DAT"),true);
       
                 //  Initialize 48 bit pseudo-random number generator
     long seed = 899432;        // Different seed, different sequence
     Random randnum = new Random(seed); 
                 //To access next random double: randnum.nextDouble()
     int imax = 29999, i = 0;
     double x = 0.5, y = 0.0, r = 0.0, xn = 0.0, yn = 0.0;
  
     for(i = 1; i <= imax;i++) {
       r = randnum.nextDouble();
       if ( r <= 0.02 )  {
        xn = 0.5;
        yn = 0.27 * y;
      }
      else if ( r > 0.02 && r <= 0.17 )   {
        xn = -0.139*x+0.263*y+0.57;
        yn = 0.246*x+0.224*y-0.036;
      }
      else if ( r>0.17 && r <= 0.3)  {
        xn = 0.17 * x - 0.215 * y + 0.408;
        yn = 0.222 * x + 0.176 * y + 0.0893;
      }
      else {
        xn = 0.781*x+0.034*y+0.1075;
        yn = -0.032*x+0.739*y+0.27;
      }
      q.println(x+"  "+y);
      x = xn;
      y = yn;
    }
    System.out.println(" ");
    System.out.println("FERN Program Complete.");
    System.out.println("Data stored in FERN.DAT");
    System.out.println(" ");
    System.out.println(" ");
    System.out.println(" ");
    System.out.println(" ");
  }
}                                                     // End of class