/** * Constructs a directed edge that references the specified nodes. * Optionally, a tet may be specified. If non-null, that tet must * reference the specified nodes. * @param a a node of the edge. * @param b a node of the edge. * @param abcd a tet that references nodes A and B; null, if none. */ public Edge(Node a, Node b, Tet abcd) { Check.argument( abcd==null || abcd.references(a,b), "tet references nodes"); _a = a; _b = b; _tet = abcd; }