load("docdraw.mac");
docdraw2d("figures/draw_head_length",
	xrange = [0,12],
	yrange = [0,8],
	vector([0,1],[5,5]),
	head_length = 1,
	vector([2,1],[5,5]),
	head_length = 0.5,
	vector([4,1],[5,5]),
	head_length = 0.25,
	vector([6,1],[5,5])
)$