struct
type t = [
| `Url of string
| `Vcf_concat of (string * t) list (* name × location *)
| `Concat of t list
| `Gunzip of t (* Should this be guessed from the URL extension? *)
| `Bunzip2 of t
| `Untar of t
]
let url u = `Url u
let vcf_concat l = `Vcf_concat l
let concat l = `Concat l
let gunzip l = `Gunzip l
let bunzip2 l = `Bunzip2 l
let untar l = `Untar l
end