[<SuppressMessage("*", "TypeNames")>]
    type posint = private Posint of int
    with
        static member OfInt =
            Constrain.constrain (fun (n : int) ->
                if n > 0
                then Success (Posint n)
                else failf "Expected positive int, received %d" n)
        member this.Value = let (Posint v) = this in v

        // posint & int
        static member (+) (Posint p1, p2 : int) = p1 + p2
        static member (+) (p1 : int, Posint p2) = p1 + p2
        static member (*) (Posint p1, p2 : int) = p1 * p2
        static member (*) (p1 : int, Posint p2) = p1 * p2
        static member (-) (Posint p1, p2 : int) = p1 - p2
        static member (-) (p1 : int, Posint p2) = p1 - p2
        static member (/) (Posint p1, p2 : int) = p1 / p2
        static member (/) (p1 : int, Posint p2) = p1 / p2

        // posint & posint
        static member (+) (Posint p1, Posint p2) = Posint (p1 + p2)
        static member (-) (Posint p1, Posint p2) = p1 - p2
        static member (*) (Posint p1, Posint p2) = Posint (p1 * p2)
        static member (/) (Posint p1, Posint p2) = Posintz (p1 / p2)

        // posint & posintz
        static member (+) (Posint p1, Posintz p2) = Posint (p1 + p2)
        static member (-) (Posint p1, Posintz p2) = p1 - p2
        static member (*) (Posint p1, Posintz p2) = Posintz (p1 * p2)
        static member (/) (Posint p1, Posintz p2) = Posintz (p1 / p2)

        // posint & negint
        static member (+) (Posint p1, Negint p2) = p1 + p2
        static member (-) (Posint p1, Negint p2) = Posint (p1 - p2)
        static member (*) (Posint p1, Negint p2) = Negint (p1 * p2)
        static member (/) (Posint p1, Negint p2) = Negintz (p1 / p2)

        // posint & negintz
        static member (+) (Posint p1, Negintz p2) = p1 + p2
        static member (-) (Posint p1, Negintz p2) = Posint (p1 - p2)
        static member (*) (Posint p1, Negintz p2) = Negintz (p1 * p2)
        static member (/) (Posint p1, Negintz p2) = Negintz (p1 / p2)

    and
        [<SuppressMessage("*", "TypeNames")>]
        posintz = private Posintz of int
    with
        static member OfInt =
            Constrain.constrain (fun (n : int) ->
                if n >= 0
                then Success (Posintz n)
                else failf "Expected non-negative int, received %d" n)
        member this.Value = let (Posintz v) = this in v

        // posintz & int
        static member (+) (Posintz p1, p2 : int) = p1 + p2
        static member (+) (p1 : int, Posintz p2) = p1 + p2
        static member (*) (Posintz p1, p2 : int) = p1 * p2
        static member (*) (p1 : int, Posintz p2) = p1 * p2
        static member (-) (Posintz p1, p2 : int) = p1 - p2
        static member (-) (p1 : int, Posintz p2) = p1 - p2
        static member (/) (Posintz p1, p2 : int) = p1 / p2
        static member (/) (p1 : int, Posintz p2) = p1 / p2

        // posintz & posintz
        static member (+) (Posintz p1, Posintz p2) = Posintz (p1 + p2)
        static member (-) (Posintz p1, Posintz p2) = p1 - p2
        static member (*) (Posintz p1, Posintz p2) = Posintz (p1 * p2)
        static member (/) (Posintz p1, Posintz p2) = Posintz (p1 / p2)

        // posintz & posint
        static member (+) (Posintz p1, Posint p2) = Posint (p1 + p2)
        static member (-) (Posintz p1, Posint p2) = p1 - p2
        static member (*) (Posintz p1, Posint p2) = Posintz (p1 * p2)
        static member (/) (Posintz p1, Posint p2) = Posintz (p1 / p2)

        // posintz & negint
        static member (+) (Posintz p1, Negint p2) = p1 + p2
        static member (-) (Posintz p1, Negint p2) = Posint (p1 - p2)
        static member (*) (Posintz p1, Negint p2) = Negintz (p1 * p2)
        static member (/) (Posintz p1, Negint p2) = Negintz (p1 / p2)