In the previous post, I discussed designing combinator libraries that compose some property over unions. It is only fitting to throw records in the mix. type U = | A of int | B of float | C of string let UFormat = ( UnionCase A IntFormat << UnionCase B FloatFormat << UnionCase C StringFormat ) |> Union (fun a b c x -> match x with | A x -> a x | B x -> b x | C x -> c x) type R = { A : int B : float [...]