Make.2-Dtype edge = G.E.tEdge of the graph.
How to analyze one edge: given an edge and the data stored at its origin, it must compute the resulting data to be stored at its destination.
The widening operator. fun _ x -> x is correct and is equivalent to not doing widening. Note that to enforce termination, the following property should hold: for all sequence x_0, x_1, ... of data, the sequence defined by y_0 =
x_0; y_{i+1} = widening y_i x_i stabilizes in finite time.