fact: Definition common_vert_edge (c1 c2 : cell) : option vert_edge:= if Qeq_bool (right_limit c1) (left_limit c2) then find (fun v => existsb (fun v' => vert_edge_eqb v v') (cell_safe_exits_left c2)) (cell_safe_exits_right c1) else find (fun v => existsb (fun v' => vert_edge_eqb v v') (cell_safe_exits_left c1)) (cell_safe_exits_right c2).
imports: mathcomp(all_ssreflect) ZArith QArith List String OrderedType OrderedTypeEx FMapAVL