yap-6.3/packages/xml/xml.lpa.pl

/* 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( [_|_] ).