Your F# example can be more concise: type Shape = | Circle of float | Square of float let area = function | Circle r -> Math.

Your F# example can be more concise: type Shape = | Circle of float | Square of float let area = function | Circle r -> Math.PI * r * r | Square sd -> sd * sd let perimeter = function | Circle r -> 2.0 * Math.PI * r | Square sd -> sd * 4.0