// Mandelbrot program (with character constants)

val Ymin: Double = -1.3;

val Ymax: Double =  1.3;

val Ystep: Double = 0.05;  //0.025;

val Xmin: Double = -2.1;

val Xmax: Double =  1.1;

val Xstep: Double = 0.02;  //0.01;

val Maxiters: Int = 1000;

def m_iter(m: Int, x: Double, y: Double,

                   zr: Double, zi: Double) : Void = {

  if Maxiters <= m

  then print_char(' ') 

  else {

    if 4.0 <= zi*zi+zr*zr then print_char('0' + (m % 10)) 

    else m_iter(m + 1, x, y, x+zr*zr-zi*zi, 2.0*zr*zi+y) 

  }

};

def x_iter(x: Double, y: Double) : Void = {

  if x <= Xmax

  then { m_iter(0, x, y, 0.0, 0.0) ; x_iter(x + Xstep, y) }

  else skip()

};

def y_iter(y: Double) : Void = {

  if y <= Ymax

  then { x_iter(Xmin, y) ; print_char('\n') ; y_iter(y + Ystep) }

  else skip() 

};    

y_iter(Ymin)