type Reducer<'a,'b,'c> = ('a -> 'b -> 'a) -> 'a -> 'c -> 'a

​

    module Transducers =

       [<GeneralizableValue>]

       let inline map proj : Reducer<'result,'output,'input> =

          fun xf ->

            fun result input ->

                xf result (proj input)

​

       let inline conj xs x = x :: xs

       let inline toList xf input = List.fold  (xf conj) [] input

​

       let xform = map (fun i -> i + 9) >> map (fun a -> a * 5)

​