/* xml.lpa.pl : Wrapper for LPA Prolog.

 *

 * Copyright (C) 2001-2005 Binding Time Limited

 * Copyright (C) 2005-2011 John Fletcher

 *

 * Current Release: $Revision: 3.3 $

 * 

 * TERMS AND CONDITIONS:

 *

 * This program is offered free of charge, as unsupported source code. You may

 * use it, copy it, distribute it, modify it or sell it without restriction,

 * but entirely at your own risk.

 *

 * xml is intended to be a rather modular module: it should be easy to

 * build a program that can output XML, but not read it, or vice versa.

 * Similarly, you may be happy to dispense with diagnosis once you are

 * sure that your code will only try to make valid calls to xml_parse/2.

 *

 * It is intended that the code should be very portable too. Clearly,

 * some small changes will be needed between platforms, but these should

 * be limited to xml_utilities. xml_utilities contains most of the shared

 * code and most of the potentially non-portable code.

 */

:- ensure_loaded( xml_driver ).



/* atom_codes/2, number_codes/2 and throw/1 are ISO predicates, mapped to

 * the Quintus equivalent here.

 */

/** @pred  atom_codes(? _A_,? _L_) is iso 


The predicate holds when at least one of the arguments is ground
(otherwise, an error message will be displayed). The argument  _A_ will
be unified with an atom and  _L_ with the list of the ASCII
codes for the characters of the external representation of  _A_.

 
*/
atom_codes( Atom, Codes ) :-

	atom_chars( Atom, Codes ).



/** @pred  number_codes(? _A_,? _L_) is iso 


The predicate holds when at least one of the arguments is ground
(otherwise, an error message will be displayed). The argument  _A_
will be unified with a number and  _L_ with the list of the ASCII
codes for the characters of the external representation of  _A_.

 
*/
number_codes( Number, Codes ) :-

	number_chars( Number, Codes ).



/* xml_exception( +Message, +Document, +Culprit, +Path ) is a hook to

 * raise an exception to be raised in respect of a fault in the XML Term:

 * Document.

 *  - Culprit is a sub-term of Document which cannot be serialized;

 *  - Message is an atom naming the type of error;

 *  - Path is a string encoding a list of SubTerm's ancestor elements in the

 *    form <tag>{(id)}* where <tag> is the element tag and <id> is the value

 *    of any attribute _named_ id.

 */

xml_exception( Message, Document, Culprit, Path ) :-

	throw( 23, xml_error([Message,Document,Culprit,Path] ) ).



/* select( ?Element, ?List0, ?List1 ) is true if List1 is equal to List0

 * with Element removed.

 */

select( H, [H|T], T ).

select( Element, [H|T0], [H|T1] ):-

    select( Element, T0, T1 ).



/* is_list( +List ) holds when List is a list.

 */

/** @pred  is_list(+ _List_) 


True when  _List_ is a proper list. That is,  _List_
is bound to the empty list (nil) or a term with functor '.' and arity 2.

 
*/
is_list( List ) :-

	nonvar( List ),

	is_list1( List ).



is_list1( [] ).

is_list1( [_|_] ).