V8/usr/lib/ideal/lib/Arc

.IS
arc {
	var radius, center,
	start, midway, end,
	startang, midang, endang;
	var a1, b1, c1,
	a2, b2, c2;
	a1 = 2*(re(end)-re(start));
	b1 = 2*(im(end)-im(start));
	c1 = -re(start)*re(start) - im(start)*im(start)
	+ re(end)*re(end) + im(end)*im(end);
	a2 = 2*(re(end)-re(midway));
	b2 = 2*(im(end)-im(midway));
	c2 = -re(midway)*re(midway) - im(midway)*im(midway)
	+ re(end)*re(end) + im(end)*im(end);
	a1*re(center) + b1*im(center) = c1;
	a2*re(center) + b2*im(center) = c2;
	startang = atan2 (start - center);
	midang = atan2 (midway - center);
	endang = atan2 (end - center);
	radius = abs (start - center);
	radius = abs (midway - center);
	radius = abs (end - center);
	start = center + abs(radius)*cis(startang);
	end = center + abs(radius)*cis(endang);
	midway = center + abs(radius)*cis(midang);
	midway ~ start;
}
.IE