/* -*-ePiX-*- */
#include "epix.h"
using namespace ePiX;

double xi(1.5), xi1(0.7), xi2(0.5*(xi + xi1)),
  xip(-0.6), xipp(0.4), ht(0.8), eps(0.0001);

// continuous
double f1(double x)
{
  double u(x - 0.5*xipp);
  return ht - 0.5*(0.25*x + fabs(u)) + 0.1*pow(u, 4);
}

// discontinuous
double f2(double x)
{
  if (x < xip)
    return 0.75 + 0.5*(1+x)*(1+x);

  else if (x < xipp)
    return 0.5*sqrt(xi1 - x);
  else
    return 0.25 - 0.33*x*(x - 0.75)*(x - 3);
}

int main()
{
  picture(P(-1, 0), P(2, 1), "4.5 x 1.5in");

  begin();
  bold();

  line(P(xmin(), 0), P(xmax(), 0));
  line(P(0,0), P(0, ymax()));
  plot(f2, xmin(), xip - eps, 20);
  plot(f2, xip, xipp - eps, 40);
  plot(f2, xipp, xmax(), 40);

  pen(1.5);
  plot(f1, xmin(), xmax(), 120);

  bold();
  dashed();
  dash_size(6);
  line(P(xip, 0), P(xip, f2(xip - eps)));
  line(P(xipp, 0), P(xipp, f2(xipp - eps)));

  line(P(xi1, 0), P(xi1, f2(xi1)));
  line(P(xi2, 0), P(xi2, f2(xi2)));

  line(P(xi, 0), P(xi, f1(xi)));

  label(P(xmax(), 0), P(0,-4), "$X$", b);
  label(P(0, ymax()), P(4, 0), "$Y$", r);

  label(P(xip, 0), P(0, -4), "$\\xi'$", b);
  label(P(0, 0), P(0, -4), "$0$", b);
  label(P(xipp, 0), P(0, -4), "$\\xi''$", b);
  label(P(xi1, 0), P(0, -4), "$\\xi_{1}$", b);
  label(P(xi2, 0), P(0, -4), "$\\xi_{2}$", b);
  label(P(xi, 0), P(0, -4), "$\\xi$", b);

  label(P(xmax(), f1(xmax())), P(4, 0), "$C$", r);
  label(P(xip - 0.2, f2(xip - 0.2)), P(0,4), "$C'$", t);

  label(P(xip + 0.3, f2(xip + 0.3)), P(0,-4), "$C'$", b);

  label(P(xi, f2(xi)), P(0,4), "$C'$", t);
  label(P(xi, f1(xi)), P(0,4), "$P$", t);

  tikz_format();
  end();
}