First of all: revision 1981 is mine, what is important me because I was born in 1981. But what is new in my revision? If you drag nodes with left button, edge-breakpoints do not change location. If you drag nodes by right button, they do, they take up their base situation at the halfpoint of the edge.
3 \page undir_graphs Undirected graph structures
5 The primary data structures of LEMON are the graph classes.