val (@@) : 'a list -> 'a list -> 'a list;;           (* rev_append *)
val list_rmap : ('a -> 'b) -> 'a list -> 'b list;;   (* rev_map *)
val list_sortu : 'a list -> 'a list;;   (* generic comparison must work on 'a *)
val list_count : ('a -> bool) -> 'a list -> int;;
val list_prefix : int -> 'a list -> 'a list;;

val yourelate : bool ref;;

exception Timeout