Rl = reachable(D, L)
Rs = reachable(D, S)
Given a collection of vertices of a digraph, the reachable vertices are those that are on a path away from a vertices in the collection.
The object reachable is a method function.
The source of this document is in /build/reproducible-path/macaulay2-1.25.06+ds/M2/Macaulay2/packages/Graphs.m2:4048:0.