link orbits
May 2, 2001; Ralph E. Griswold
This file is in the public domain.
These procedures produce traces of orbits. See
Geometric and Artistic Graphics; Design Generation with
Microcomputers, Jean-Paul Delahaye, Macmillan, 1987, pp. 65-73.
The arguments specify the starting positions, the extent of the
drawing, the number of segments, and various parameters that
control the orbit.