(*
  Sample changes to a PXP (an OCaml XML parser) XML tree

  Copyright (C) <2003> Stefano Zacchiroli <zack@cs.unibo.it>
  This program is free software; you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation; either version 2 of the License, or
  (at your option) any later version.
  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.
  You should have received a copy of the GNU General Public License
  along with this program; if not, write to the Free Software
  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*)
open Pxp_document;;
open Pxp_dtd;;
open Pxp_types;;
open Pxp_yacc;;
  (*z facility function to parse a well formed (validation is not performed!)
  XML document from the file named in ’fname’ argument. It returns a PXP
  "document". *)
let parse_xml fname =
  parse_wfdocument_entity default_config (from_file fname) default_spec
in
  (*z use the above function to parse XML document contained in file passed on
  command line *)
let document = parse_xml Sys.argv.(1) in
  (*z get root element of the above XML document, this is the beginning of the
  XML tree *)
let root = document#root in
  (*z find the first "c" node of the XML tree, find is performed using
  "find_element" function telling it to depply travel the XML tree ’root’ *)
let c_node = find_element deeply:true "c" root in
  (*z get data child of ’c’ node. Note that we use here the assumption that
  first child of ’c’ node is a data node *)
let c_data = c_node#nth_node 0 in
  (*z change ’c’ node string data to a sample string *)
c_data#set_data "Hello, PXP World!";
  (*z dump (modified) xml output to stdout *)
root#write (`Out_channel stdout) `Enc_utf8