// Shows duals for points and lines.
// 3/27/05 BPW

#include <stdio.h>
#include <math.h>

// These map coordinates to 0 ... 530
#define TRANSX(X) (530.0*((X)-xmin)/diff)
#define TRANSY(Y) (530.0*((Y)-ymin)/diff)

main()
{
float diff=24.0,xmin=(-12.0),ymin=(-12.0);
float m,b,x,y;
int map;
char pointLabel='a',lineLabel='A';

fprintf(stderr,"Enter map # in 1..7\n");
scanf("%d",&map);
if (map<1 || map>7)
  exit(0);

printf("%%!PS\n");
printf("%%%%BoundingBox: 0 0 605 755\n");
/* The +72 shifts the figure one inch from the lower left corner */
printf("40 155 translate\n");
printf("/Helvetica findfont\n");
printf("12 scalefont\n");
printf("setfont\n");

//Mark origin
printf("%f %f 3 0 360 arc stroke\n",TRANSX(0.0),TRANSY(0.0));

fprintf(stderr,"Enter points to dualize (-99 -99 to terminate)\n");
fprintf(stderr,"Output will be heavy\n");
while (1)
{
  scanf("%f %f",&x,&y);
  if (x>50.0 || x<(-50.0))
    break;
  printf("newpath\n");
  printf("%f %f 3 0 360 arc fill\n",TRANSX(x),TRANSY(y));
  printf("%f %f moveto\n",TRANSX(x)+5.0,TRANSY(y)-2.0);
  printf("(%c) show\n",pointLabel++);
  switch (map)
  {
  case 1:
    m=(-x/y);
    b=(-1.0/y);
    break;
  case 2:
    m=x;
    b=y;
    break;
  case 3:
    m=x*2.0;
    b=(-y);
    break;
  case 4:
    m=(-x/y);
    b=1.0/y;
    break;
  case 5:
    m=x;
    b=(-y);
    break;
  case 6:
    m=x/y;
    b=1.0/y;
    break;
  case 7:
   m=(-x);
   b=y;
  }
  printf("newpath\n");
  // Line in dual
  fprintf(stderr,"slope & y-intercept: %f %f\n",m,b);
  printf("%f %f moveto\n",TRANSX(-10.0),TRANSY(-12.0*m+b));
  printf("%f %f lineto\n",TRANSX(10.0),TRANSY(12.0*m+b));
  printf("stroke\n");
  printf("newpath\n");
  printf("%f %f 2 0 360 arc stroke\n",TRANSX(0.0),TRANSY(b));
  printf("%f %f moveto\n",TRANSX(0.0)+5.0,TRANSY(b)-2.0);
  printf("(%c) show\n",lineLabel++);
}

printf("0 setlinewidth\n");
fprintf(stderr,"Enter slope and intercept for lines to dualize\n");
fprintf(stderr,"Output will be light\n");
printf("0.5 setgray\n");
// Lines next
while (1)
{
  scanf("%f %f",&m,&b);
  if (b>50.0 || b<(-50.0))
    break;
  printf("%f %f moveto\n",TRANSX(-50.0),TRANSY(-50.0*m+b));
  printf("%f %f lineto\n",TRANSX(50.0),TRANSY(50.0*m+b));
  printf("stroke\n");
  switch (map)
  {
  case 1:
    y=(-1.0/b);
    x=(-m*y);
    break;
  case 2:
    x=m;
    y=b;
    break;
  case 3:
    x=m/2.0;
    y=(-b);
    break;
  case 4:
    y=1.0/b;
    x=(-m*y);
    break;
  case 5:
    x=m;
    y=(-b);
    break;
  case 6:
    y=1.0/b;
    x=m*y;
    break;
  case7:
    x=(-m);
    y=b;
  }
  // Point in dual
  fprintf(stderr,"x & y: %f %f\n",x,y);
  printf("newpath\n");
  printf("%f %f 2 0 360 arc fill\n",TRANSX(x),TRANSY(y));
}

printf("showpage\n");
printf("%%EOF\n");
}