static LL<DoubleRect> gridOfDoubleRects3(double w, double h, int cols, int rows) {
  ret gridOfDoubleRects3(DoubleRect(0, 0, w, h), cols, rows);
}

static LL<DoubleRect> gridOfDoubleRects3(DoubleRect r, int cols, int rows) {
  new LL<DoubleRect> l;
  for row to rows: {
    new L<DoubleRect> line;
    double y1 = r.y+r.h*row/rows;
    double y2 = r.y+r.h*(row+1)/rows;
    for col to cols: {
      double x1 = r.x+r.w*col/cols;
      double x2 = r.x+r.w*(col+1)/cols;
      line.add(DoubleRect(x1, y1, x2-x1, y2-y1));
    }
    l.add(line);
  }
  ret l;
}

Began life as a copy of #1024667