/* 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; & CC Bordeianu, Univ Bucharest, 2007
   Support by National Science Foundation
*/
//   fern.c: Create fractal, fern-like pattern     

#include <stdio.h>
#include <stdlib.h>

// if you don't have drand48 uncomment the following two lines 
    #define drand48 1.0/RAND_MAX*rand 
    #define srand48 srand                   
#define max 30000                             // number of iterations
#define seed 68111                       // seed for number generator
    
main() {    
	int i;
  double x, y, xn, yn, r;
	
  FILE *output;                              // save data in fern.dat
  output = fopen("fern.dat","w");
	                                           // seed number generator
  srand48(seed);          
	                                                  // starting point
  x    = 0.5;                                            
  y    = 0.0;
  for (i = 1; i<= max; i++) {                           // iterations
    r = drand48();
		                                                       // case 1
    if (r <=  0.02)   {                                    
      xn= 0.5;
      yn= 0.27*y;
    }
		                                                       // case 2
    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;
    }
		                                                        // case 3
    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;
    }  
		                                                       // case 4
    else  {                                                       
      xn= 0.781*x + 0.034*y + 0.1075;
      yn= -0.032*x + 0.739*y + 0.27;
    }  
    fprintf(output, "%f %f\n", x, y);   
    x = xn;
    y = yn;
  }
  printf("data stored in fern.dat\n");
  fclose(output);
}