optional_parameters.fs

type A = { a1: int; a2: int; a3: int }
type B = { b1: int; b2: int; b3: int }
type C = { c1: int; c2: int; c3: int }

type T =
    static member M(?a1: int, ?a2: int, ?a3: int, 
                    ?b1: int, ?b2: int, ?b3: int, 
                    ?c1: int, ?c2: int, ?c3: int) = ()

let a: A option = None
let b: B option = None
let c: C option = None

T.M(
    ?a1 = (a |> Option.map (fun x -> x.a1)),
    ?a2 = (a |> Option.map (fun x -> x.a2)),
    ?a3 = (a |> Option.map (fun x -> x.a3)),

    ?b1 = (b |> Option.map (fun x -> x.b1)),
    ?b2 = (b |> Option.map (fun x -> x.b2)),
    ?b3 = (b |> Option.map (fun x -> x.b3)),
    
    ?c1 = (c |> Option.map (fun x -> x.c1)),
    ?c2 = (c |> Option.map (fun x -> x.c2)),
    ?c3 = (c |> Option.map (fun x -> x.c3)))