rw is a program that calculates rank-width and rank-decompositions.
It is based on ideas from "Computing rank-width exactly" by Sang-il Oum,
"Sopra una formula numerica" by Ernesto Pascal, "Generation of a Vector
from the Lexicographical Index" by B.P. Buckles and M. Lybanon and "Fast
additions on masked integers" by Michael D. Adams and David S. Wise.