abstraction over pull and push sources

dataflow.fsx

type 'a Source =
    | Push of (('a Option -> Unit) -> Unit)
    | Pull of (Unit -> 'a Option)

type 'a Destination =
    | Destination of ('a Option -> Unit)

type Converter<'a,'b> =
    | Converter of ('a Option -> 'b Option)
    
let combine conveter1  conveter2 = 
    match (conveter1, conveter2) with
        | (Converter(a),Converter(b)) -> Converter(fun x -> b(a(x)))

let combine1 source conveter = 
    match (source, conveter) with
        | (Push(a),Converter(b)) -> Push(fun f -> a(fun x -> f(b(x))))
        | (Pull(a),Converter(b)) -> Pull(fun () -> b(a()))

let combine2 conveter destination = 
    match (conveter, destination) with
        | (Converter(a),Destination(b)) -> Destination(fun v -> b(a(v)))