/* tiles.c: program to fill in a deficient 2^n by 2^n square with trominoes
   Call with:  "tiles <square size> <missing x> <missing y>"*/

#include <stdio.h>
double scale;

tri_fill(int half_size,int x_center,int y_center,float x_missing,
	 float y_missing)
     /* half_size is half the width of the square to be filled
	(x_center,y_center) is its center and
	(x_missing,y_missing) are the coordinates of the center of
	missing square to be filled */

     /* Note that all squares are passed by their centers as this has the
	advantage of rotational symmetry */

{
  int x_dir,y_dir,quarter_size;
  double x1,x2,x4,y1,y3,y5;
  x_dir=(x_missing>=x_center)?1:-1;
  y_dir=(y_missing>=y_center)?1:-1;
  x1=(x_center-x_dir*0.9)*scale; x2=(x_center+x_dir*0.9)*scale;
  x4=(x_center-x_dir*0.1)*scale; y1=(y_center-y_dir*0.9)*scale;
  y3=(y_center-y_dir*0.1)*scale; y5=(y_center+y_dir*0.9)*scale;
  /* Fill in the L shape at the center in the three boxes in directions
     other than the (x_dir,y_dir) direction */
  printf("n %.2lf %.2lf m %.2lf %.2lf l %.2lf %.2lf l ",x1,y1,x2,y1,x2,y3);
  printf("%.2lf %.2lf l %.2lf %.2lf l %.2lf %.2lf l ",x4,y3,x4,y5,x1,y5);
  printf("%.2lf %.2lf l cp doit\n",x1,y1);
  /* If the half-size is 1, we're done. Otherwise, fill in the
     four deficient squares that are remaining of half the side length */
  if (half_size>1) {
    quarter_size=half_size/2;
    tri_fill(quarter_size,x_center-quarter_size*x_dir,
	     y_center+quarter_size*y_dir,x_center-x_dir*0.5,
	     y_center+y_dir*0.5);
    tri_fill(quarter_size,x_center-quarter_size*x_dir,
	     y_center-quarter_size*y_dir,x_center-x_dir*0.5,
	     y_center-y_dir*0.5);
    tri_fill(quarter_size,x_center+quarter_size*x_dir,
	     y_center-quarter_size*y_dir,x_center+x_dir*0.5,
	     y_center-y_dir*0.5);
    tri_fill(quarter_size,x_center+quarter_size*x_dir,
	     y_center+quarter_size*y_dir,x_missing,y_missing);
  }
}

main(int argc,char **argv)
{
  int n,x_missing,y_missing;
  if (argc!=4) {
    fprintf(stderr,"Usage: tiles <size> <missing x> <missing y>.\n");
    fprintf(stderr,"Size must be a power of 2\n");
    exit(-1);
  }
  sscanf(argv[1],"%d",&n);
  /* Print out postscript header*/
  printf("%%!PS-Adobe-1.0\n%%%%Pages: (atend)\n");
  printf("%%%%BoundingBox:0 0 500 720\n%%%%Endcomments\n\n",n,n);
  /* Postscript Macro definitions */
  printf("/n{ newpath} def\n/m{ moveto} def\n/l{ lineto} def\n");
  printf("/doit {gsave stroke grestore} def\n");
  printf("/cp{ closepath} def\n\n0 setlinewidth\n\n%%Prog begin\n\n");
  sscanf(argv[2],"%d",&x_missing);
  sscanf(argv[3],"%d",&y_missing);
  scale=500.0/n;
  /* Fill in the missing square */
  printf("n %.1lf %.1lf m ",(x_missing-0.1)*scale,(y_missing-0.1)*scale);
  printf("%.1lf %.1lf l ",(x_missing-0.9)*scale,(y_missing-0.1)*scale);
  printf("%.1lf %.1lf l ",(x_missing-0.9)*scale,(y_missing-0.9)*scale);
  printf("%.1lf %.1lf l ",(x_missing-0.1)*scale,(y_missing-0.9)*scale);
  printf("cp gsave eofill grestore\n");
  /* Fill the remaining region */
  tri_fill(n/2,n/2,n/2,x_missing-0.5,y_missing-0.5);
}