sig
type elt
type 'a container
val length : 'a container -> int
val is_empty : 'a container -> bool
val iter : 'a container -> f:(elt -> unit) -> unit
val fold : 'a container -> init:'b -> f:('b -> elt -> 'b) -> 'b
val exists : 'a container -> f:(elt -> bool) -> bool
val for_all : 'a container -> f:(elt -> bool) -> bool
val find : 'a container -> f:(elt -> bool) -> elt option
val to_list : 'a container -> elt list
val to_array : 'a container -> elt array
val container : (elt, 'a container) Container.type_class
end