F#でThreadLocal等の副作用もないバージョン。

type MainBuilder() =
    member this.Return x =
        x |> List.map (function
        | _, Some names -> box names
        | number, None -> box number)
let main = MainBuilder()

let makeFizzBuzz name condition (x : obj) =
    match x with
    | :? int as number -> number, if condition number then Some name else None
    | _ ->
        let number, names = x :?> int * string option
        number, if condition number then (defaultArg names "") + name |> Some else names

// fizz, buzz, gizzの定義は>>341と同じなので省略

> main { return [1; 3; 5; 7; 15; 21; 35; 105] |> List.map (fun x -> gizz(buzz(fizz x))) };;
val it : obj list =
  [1; "Fizz"; "Buzz"; "Gizz"; "FizzBuzz"; "FizzGizz"; "BuzzGizz"; "FizzBuzzGizz"]