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

int i;
float x,y;
FILE *outfile;

#define NPTS 830
#define PAGE_WIDTH 8
#define PAGE_HEIGHT 10

#define PI 3.14159265359879323846

const double THETA = PI/2.4;
const double T = .0001;

float X0 = -.9;
float Y0 = .5;
float V0 = .009;
float F = .004;
float g = -1.98;
float t = 0;
float px = X0;
float py = Y0;
float vy = V0*sin(THETA);
float vx = V0*cos(THETA);


main() {

  outfile = fopen("ball.eps", "w");
  fprintf(outfile,"%%! ball output\n");
  fprintf(outfile,"%%%%BoundingBox: 0 0 %f %f\n",
	  72.0*PAGE_WIDTH,72.0*PAGE_HEIGHT);
  fprintf(outfile,"gsave\n");
  fprintf(outfile,"/l {lineto} def\n");
  fprintf(outfile,"%f %f scale\n",72.0*PAGE_WIDTH*0.5,
	  72.0*PAGE_HEIGHT*0.5);
  fprintf(outfile,"90 rotate\n");
  fprintf(outfile,"1 -1 translate\n");
  fprintf(outfile,"0.5 setgray 0.02 setlinewidth\n");
  px = X0;
  py = Y0;
  fprintf(outfile,"%.3f %.3f moveto\n",px,py);


  for (i = 1; i < NPTS; i++) {
    
    vy = vy + g*T;
    px = px + vx;
    py = py + vy;

    //    x = (2.0*i + 1.0 - NPTS)/NPTS;
    //    y = sin(50.0*x)/(50.0*x);

    //    x = (px + 1.0- NPTS)/NPTS;
    //    y = (py + 1.0- NPTS)/NPTS;
    
    if (py <= -1 || py >= 1) {
      if (vy != 0) {
	if (vy < F && vy > -F) {
	  vy = 0;
	} else {
	  vy = vy > 0 ? vy-F : vy+F;
	  vy = -vy;
	}
      }
    }
    if (px <= -1 || px >= 1) {
      if (vx != 0) {
	if (vx < F && vx > -F) {
	  vx = 0;
	} else {
	  vx = vx > 0 ? vx-F : vx+F;
	  vx = -vx;
	}
      }
    }

    if (px > 1) {
      px = 1;
    } else if (px < -1) {
      px = -1;
    }

    if (py > 1) {
      py = 1;
    } else if (py < -1) {
      py = -1;
    }

    fprintf(outfile,"%.3f %.3f l\n",px,py);
    t+=T;
  }

  fprintf(outfile,"stroke\n");
  fprintf(outfile,"grestore\n");
  fprintf(outfile,"showpage\n");
  fclose(outfile);

}