allOrNone.fs

 // direct-ish translation
let allOrNone (xs : 'a option list) : 'a list option =
    List.foldBack
        (fun x st -> x |> Option.bind (fun x -> st |> Option.bind (fun st -> Some (x::st))))
        xs
        (Some [])
 
 // shorter
let allOrNone2 (xs : 'a option list) : 'a list option =
    List.foldBack
        (fun x -> Option.bind (fun st -> x |> Option.map (fun x -> x::st)))
        xs
        (Some [])
 
// bails out early
let allOrNone3 xs =
    let rec recAllOrNone cont = function
    | (Some x :: xs) -> recAllOrNone (fun r -> cont (x :: r)) xs
    | (None :: _) -> None 
    | _ -> cont []
     
    recAllOrNone Some xs