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reflectionocamlenumerationdisjoint-union

Is enumeration over custom union type possible?

Having a disjoint union type like this:

type yolo = | A | B | C

Is it possible in OCaml to iterate/enumerate over each possible value of type yolo without prior knowledge of how many/what these values are?

What I want to achieve is a function that takes a type and returns a list with all of its values. For example:

let yolos = extractor yolo
val yolos : yolo list = [A; B; C]

(I am looking for a way to implement extractor function from the above snippet)

In F# my goal is achievable with something similar to this:

open Microsoft.FSharp.Reflection

type yolo =
    | A
    | B
    | C
let yolos = FSharpType.GetUnionCases typeof<yolo>
Solution

  • Yes, it is possible. It looks like you're looking for Jane Street's ppx_enumerate which does exactly this, even working with polymorphic types.