Basic URLs.

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/Pure/General/url.ML	Wed May 12 16:51:52 1999 +0200
@@ -0,0 +1,67 @@
+(*  Title:      Pure/General/url.ML
+    ID:         $Id$
+    Author:     Markus Wenzel, TU Muenchen
+
+Basic URLs.
+*)
+
+signature URL =
+sig
+  type T
+  val file: Path.T -> T
+  val http: string * Path.T -> T
+  val ftp: string * Path.T -> T
+  val append: T -> T -> T
+  val pack: T -> string
+  val unpack: string -> T
+end;
+
+structure Url: URL =
+struct
+
+
+(* type url *)
+
+datatype scheme = File | Http of string | Ftp of string;
+
+datatype T = Url of scheme * Path.T;
+
+fun file p = Url (File, p);
+fun http (h, p) = Url (Http h, p);
+fun ftp (h, p) = Url (Ftp h, p);
+
+
+(* append *)
+
+fun append (Url (s, p)) (Url (File, p')) = Url (s, Path.append p p')
+  | append _ url = url;
+
+
+(* pack *)
+
+fun pack_scheme File = ""
+  | pack_scheme (Http host) = "http://" ^ host
+  | pack_scheme (Ftp host) = "ftp://" ^ host;
+
+fun pack (Url (s, p)) = pack_scheme s ^ (if Path.is_current p then "" else Path.pack p);
+
+
+(* unpack *)
+
+fun scan_lits [] x = ("", x)
+  | scan_lits (c :: cs) x = (($$ c -- scan_lits cs) >> op ^) x;
+
+val scan_literal = scan_lits o Symbol.explode;
+
+val scan_path = Scan.any Symbol.not_eof >> (Path.unpack o implode);
+val scan_host = Scan.any1 (not_equal "/" andf Symbol.not_eof) >> implode;
+
+val scan_url =
+  scan_literal "http://" |-- scan_host -- scan_path >> http ||
+  scan_literal "ftp://" |-- scan_host -- scan_path >> ftp ||
+  Scan.unless (scan_literal "http:" || scan_literal "ftp:") scan_path >> file;
+
+fun unpack s = Symbol.scanner "Malformed URL" scan_url (Symbol.explode s);
+
+
+end;