Computation of the set-valued function F on the nodes V of a digraph G=(V,E), such that, for all x,y in V, F(x) is the smallest set satisfying (1) F(x) >= F'(x), and (2) F(x) >= F(y) if (x,y) in E. The computation effectively computes the strongly connected components of G using Tarjan's algorithm (as streamlined by Eve and Kurko-Suonio). <p> The digraph nodes are passed to the algorithm as an <code>Indexed [] nodes</code> (which will imply the node traversal order). For <code>x, y</code> from <code>nodes[]</code> it is required that <code>x <> y</code> implies <code>x.index <> y.index</code>.