# Mandelbrot set generator: simple example of Miller DSL as programming language.
begin {
  # Set defaults. They can be overridden by e.g.
  #   mlr -n put -e 'begin{@maxits=200}' -f nameofthisfile.mlr
  # or
  #   mlr -n put -s maxits=200 -f nameofthisfile.mlr
  @rcorn     ??= -2.0;
  @icorn     ??= -2.0;
  @side      ??=  4.0;
  @iheight   ??=   50;
  @iwidth    ??=  100;
  @maxits    ??=  100;
  @levelstep ??=    5;
  @chars     ??= "@X*o-.";
  @silent    ??= false;
  @do_julia  ??= false;
  @jr        ??= 0.0;      # Real part of Julia point, if any
  @ji        ??= 0.0;      # Imaginary part of Julia point, if any
}

end {
  if (!@silent) {
    print "RCORN     = ".@rcorn;
    print "ICORN     = ".@icorn;
    print "SIDE      = ".@side;
    print "IHEIGHT   = ".@iheight;
    print "IWIDTH    = ".@iwidth;
    print "MAXITS    = ".@maxits;
    print "LEVELSTEP = ".@levelstep;
    print "CHARS     = ".@chars;
  }

  for (int ii = @iheight-1; ii >= 0; ii -= 1) {
    num ci = @icorn + (ii/@iheight) * @side;
    for (int ir = 0; ir < @iwidth; ir += 1) {
      num cr = @rcorn + (ir/@iwidth) * @side;
      str c = get_point_plot(cr, ci, @maxits, @do_julia, @jr, @ji);
      if (!@silent) {
        printn c
      }
    }
    if (!@silent) {
      print;
    }
  }
}

func get_point_plot(num pr, num pi, int maxits, bool do_julia, num jr, num ji): str {
  num zr = 0.0;
  num zi = 0.0;
  num cr = 0.0;
  num ci = 0.0;

  if (!do_julia) {
    zr = 0.0;
    zi = 0.0;
    cr = pr;
    ci = pi;
  } else {
    zr = pr;
    zi = pi;
    cr = jr;
    ci = ji;
  }

  int iti = 0;
  bool escaped = false;
  num zt = 0;
  for (iti = 0; iti < maxits; iti += 1) {
    num mag = zr*zr + zi+zi;
    if (mag > 4.0) {
        escaped = true;
        break;
    }
    # z := z^2 + c
    zt = zr*zr - zi*zi + cr;
    zi = 2*zr*zi + ci;
    zr = zt;
  }
  if (!escaped) {
    return ".";
  } else {
    int level = (iti // @levelstep) % strlen(@chars);
    return substr(@chars, level, level);
  }
}