/*******************************************************
The following //comment lines identify ngcgui inputs:

example option:
//ngcgui: --precision 6

info message (appears on ngcgui tab page):
//ngcgui: info: gcmc drill example (inch units)

variables with defaults:
//ngcgui: nx=4
//ngcgui: ny=3
//ngcgui: xstart=1
//ngcgui: ystart=1
//ngcgui: xspacing=0.5
//ngcgui: yspacing=1.0
//ngcgui: retract=0.1
//ngcgui: increment=0.5
//ngcgui: repeat=1
//ngcgui: fr=10,feedrate

variable with comment text:
//ngcgui: zdepth=0 , z(neg typ)
*******************************************************/

feedrate(fr);

x=xstart;
y=ystart;
sign = 1;

for (i = 0; i < nx ; i++) {
  for (j = 0; j < ny; j++) {
    drill([x, y, zdepth], retract, increment, repeat);
    y = y + sign * yspacing;
  }
  y = y - sign * yspacing;
  sign = -1 *sign;
  x = x + xspacing;
}