fact: Definition edge_below (e1 : edge) (e2 : edge) : bool := (point_under_edge (left_pt e1) e2 && point_under_edge (right_pt e1) e2) || (negb (point_strictly_under_edge (left_pt e2) e1) && negb (point_strictly_under_edge (right_pt e2) e1)).
imports: mathcomp(all_ssreflect) ZArith QArith List String OrderedType OrderedTypeEx FMapAVL