# Module Univ_map.With_fold

    module With_fold: sig .. end

keys that map to an accumulator value with an associated fold operation

    module Key: sig .. end

    val set : t -> ('a, 'b) Key.t -> 'b -> t

reset the accumulator

    val find : t -> ('a, 'b) Key.t -> 'b

the current accumulator

    val add : t -> ('a, 'b) Key.t -> 'a -> t

fold value into accumulator

    val change : t -> ('a, 'b) Key.t -> ('b -> 'b) -> t

accumulator update