/*-----------------------------------------------------------------------------
| File: koch.c [ANSI-C conforming source code]
| Created: May 8, 2006, Fredrik Jonsson <fj@phys.soton.ac.uk>
| Last modified: May 8, 2006, Fredrik Jonsson <fj@phys.soton.ac.uk>
| Description:
|    The KOCH program creates data sets corresponding to the Koch fractal,
|    for the purpose of acting as test objects for the program BOXCOUNT,
|    which calculates box-counting estimates to the fractal dimension.
|    The program is simply executed by 'koch <N>', where <N> is an integer
|    describing the maximum depth of recursion that is to be used in the
|    generation of the data set for the fractal. If invoked without any
|    arguments present at the command line, a default value of <N>=6 is
|    assumed. The generated data stream is sent to standard terminal output,
|    easy to pipe into files (as suitable for the BOXCOUNT program) or as
|    feeds to other programs of data analysis.
|
| Compile with: gcc -O2 -g -Wall -pedantic -ansi koch.c -o koch -lm
|
| Copyright (C) 2006 Fredrik Jonsson <fj@phys.soton.ac.uk>
=============================================================================*/
#include <math.h>
#include <stdio.h>

extern char *optarg;

void kochsegment(double xa,double ya,double xb,double yb,
   int depth,int maxdepth) {
   double xca,yca,xcb,ycb,xcc,ycc;
   if (depth==maxdepth) {
      fprintf(stdout,"%2.8f %2.8f\n",xb,yb);
   } else {
      xca=xa+(xb-xa)/3.0;
      yca=ya+(yb-ya)/3.0;
      xcb=xb-(xb-xa)/3.0;
      ycb=yb-(yb-ya)/3.0;
      xcc=(xa+xb)/2.0-(yb-ya)/(2.0*sqrt(3.0));
      ycc=(ya+yb)/2.0+(xb-xa)/(2.0*sqrt(3.0));
      kochsegment(xa,ya,xca,yca,depth+1,maxdepth);
      kochsegment(xca,yca,xcc,ycc,depth+1,maxdepth);
      kochsegment(xcc,ycc,xcb,ycb,depth+1,maxdepth);
      kochsegment(xcb,ycb,xb,yb,depth+1,maxdepth);
   }
}

int main(int argc, char *argv[]) {
   int maxdepth=6;
   if (argc>1) sscanf(argv[1],"%d",&maxdepth);
   if (maxdepth>0) {
      fprintf(stdout,"%2.8f %2.8f\n",0.0,1.0);
      kochsegment(0.0,1.0,sqrt(3.0)/2.0,-0.5,1,maxdepth);
      kochsegment(sqrt(3.0)/2.0,-0.5,-sqrt(3.0)/2.0,-0.5,1,maxdepth);
      kochsegment(-sqrt(3.0)/2.0,-0.5,0.0,1.0,1,maxdepth);
   }
   return(0);
}