val list_uniq:
?eq:('a->'a->bool) -> 'a list -> 'a list (** uniq unix filter on lists *)
val filter_map: ('a -> 'b option) -> 'a list -> 'b list (** filter + map *)
+val filter_map_acc: ('acc -> 'a -> ('acc * 'b) option) -> 'acc -> 'a list ->
+ 'acc * 'b list (** fold/filter + map *)
+
val list_rev_map_filter: ('a -> 'b option) -> 'a list -> 'b list
val list_rev_map_filter_fold: ('c -> 'a -> 'c * 'b option) -> 'c -> 'a list -> 'c * 'b list
val list_concat: ?sep:'a list -> 'a list list -> 'a list (**String.concat-like*)