Re: [Libguestfs] [PATCH v11 6/6] New tool: virt-builder-repository

> +let osinfo_ids = ref None > + > +let osinfo_get_short_ids () = > + match !osinfo_ids with > + | Some ids -> ids > + | None -> ( > + let set = ref StringSet.empty in > + Osinfo.iterate_db ( > + fun filepath -> > + let doc = Xml.parse_file filepath in > + let xpathctx = Xml.xpath_new_context doc in > + let nodes = xpath_get_nodes xpathctx "/libosinfo/os/short-id" in > + List.iter ( > + fun node -> > + let id = Xml.node_as_string node in > + set := StringSet.add id !set > + ) nodes > + ); > + osinfo_ids := Some (!set); > + !set > + ) If the Osinfo module implemented a ‘fold’ function (instead of iter) then you could write this much more conveniently. It would be something like: let set = Osinfo.fold (fun set filepath -> ...) StringSet.empty in where the ‘...’ bit non-imperatively updates ‘set’.