val join : ('a -> 'a -> 'a) -> 'a -> 'a list -> 'a listval widen : (E.t -> E.t -> 'a) -> E.t -> E.t list -> 'a listval meet : ('a -> 'b -> 'c) -> 'a -> 'b list -> 'c listval merge_element :
(E.t -> 'a list -> 'a list) ->
E.t ->
'a list Map.t ->
'a list Map.t