Untyped XML trees and YXML notation: minimal bootstrap version.
*)
(** XML **)
signature XML = sig type attributes = (string * string) list datatype tree =
Elem of (string * attributes) * tree list
| Text ofstring type body = tree list val xml_elemN: string val xml_nameN: string val xml_bodyN: string val wrap_elem: ((string * attributes) * body) * body -> tree val unwrap_elem: tree -> (((string * attributes) * body) * body) option val unwrap_elem_body: tree -> body option val traverse_text: (string -> 'a -> 'a) -> tree -> 'a -> 'a val traverse_texts: (string -> 'a -> 'a) -> body -> 'a -> 'a val content_of: body -> string end
structure XML: XML = struct
type attributes = (string * string) list;
datatype tree =
Elem of (string * attributes) * tree list
| Text ofstring;
type body = tree list;
(* wrapped elements *)
val xml_elemN = "xml_elem"; val xml_nameN = "xml_name"; val xml_bodyN = "xml_body";
fun wrap_elem (((a, atts), body1), body2) =
Elem ((xml_elemN, (xml_nameN, a) :: atts), Elem ((xml_bodyN, []), body1) :: body2);
fun unwrap_elem (Elem ((name, (n, a) :: atts), Elem ((name', []), body1) :: body2)) = if name = xml_elemN andalso n = xml_nameN andalso name' = xml_bodyN then SOME (((a, atts), body1), body2) else NONE
| unwrap_elem _ = NONE;
fun unwrap_elem_body (Elem ((name, (n, _) :: _), Elem ((name', []), _) :: body)) = if name = xml_elemN andalso n = xml_nameN andalso name' = xml_bodyN then SOME body else NONE
| unwrap_elem_body _ = NONE;
(* traverse text content *)
fun traverse_text f tree =
(case unwrap_elem_body tree of
SOME ts => traverse_texts f ts
| NONE =>
(case tree of
Elem (_, ts) => traverse_texts f ts
| Text s => f s)) and traverse_texts _ [] res = res
| traverse_texts f (t :: ts) res = traverse_texts f ts (traverse_text f t res);
fun content_of body = String.concat (rev (traverse_texts (fn x => fn xs => x :: xs) body []));
end;
(** YXML **)
signature YXML = sig val X_char: char val Y_char: char val X: string val Y: string val XY: string val XYX: string val detect: string -> bool val output_markup: string * XML.attributes -> string * string end;
structure YXML: YXML = struct
(* markers *)
val X_char = Char.chr 5; val Y_char = Char.chr 6;
val X = String.str X_char; val Y = String.str Y_char; val XY = X ^ Y; val XYX = XY ^ X;
fun detect s = Char.contains s X_char orelse Char.contains s Y_char;
(* output markup *)
fun output_markup ("", _) = ("", "")
| output_markup (name, atts) = let val bgs = XY :: name :: List.foldr (fn ((a, b), ps) => Y :: a :: "=" :: b :: ps) [X] atts; val en = XYX; in (String.concat bgs, en) end;
end;
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