Union type with units of measure

UnitsOfMeasure.fs

module UnitsOfMeasure

[<Measure>] type cm
[<Measure>] type inch

type Shape<[<Measure>]'u> =
    | Circle of float<'u>
    | Square of float<'u>
    | Triangle of float<'u> * float<'u>
    | Rectangle of float<'u> * float<'u>

let GetArea shape =
    match shape with
    | Circle(radius) -> 3.14 * radius * radius
    | Square(width) -> width * width
    | Triangle(``base``, height) -> ``base`` * height / 2.0
    | Rectangle(width, height) -> width * height