+ val filter_open : (goal * switch) list -> (goal * switch) list
+ val is_open: goal * switch -> bool
+ val is_fresh: goal * switch -> bool
+ val init_pos: (goal * switch) list -> (goal * switch) list
+ val goal_of_loc: goal * switch -> goal
+ val switch_of_loc: goal * switch -> switch
+ val zero_pos : goal list -> (goal * switch) list
+ val deep_close: goal list -> t -> t
+
+
+ val ( @+ ) : 'a list -> 'a list -> 'a list
+ val ( @- ) : 'a list -> 'a list -> 'a list
+ val ( @~- ) : ('a * switch) list -> goal list -> ('a * switch) list
+
+