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yap-6.3/Logtalk/examples/dcgs/xml.lgt
pmoura e8e39e597b Logtalk 2.15.4 release files.
git-svn-id: https://yap.svn.sf.net/svnroot/yap/trunk@843 b08c6af1-5177-4d33-ba66-4b1c6b8b522a
2003-07-09 00:20:55 +00:00

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:- object(xml).
:- info([
version is 1.0,
date is 2003/7/7,
author is 'Paulo Moura',
comment is 'Conversion between compound terms and XML.']).
:- public(convert/3).
:- mode(convert(@compound, @compound, -atom), zero_or_one).
:- mode(convert(-compound, -compound, +atom), zero_or_one).
:- info(convert/3, [
comment is 'Converts between a compound term and an interpretation and XML.',
argnames is ['Term', 'Interpretation', 'XML']]).
convert(Term, Interpretation, XML) :-
var(XML) ->
phrase(term(Term, Interpretation), List),
atom_codes(XML, List)
;
atom_codes(XML, List),
phrase(term(Term, Interpretation), List).
term(Term, Interpretation) -->
{nonvar(Term), nonvar(Interpretation),
Interpretation =.. [Functor| Tags], Term =.. [Functor| Args]},
open_tag(Functor),
arguments(Tags, Args),
close_tag(Functor).
term(Term, Interpretation) -->
{var(Term), var(Interpretation)},
open_tag(Functor),
arguments(Tags, Args),
close_tag(Functor),
{Interpretation =.. [Functor| Tags], Term =.. [Functor| Args]}.
arguments([], []) -->
[].
arguments([Tag| Tags], [Arg| Args]) -->
open_tag(Tag),
value(Arg),
close_tag(Tag),
arguments(Tags, Args).
open_tag(Tag) -->
"<", value(Tag), ">".
close_tag(Tag) -->
"</", value(Tag), ">".
value(Value) -->
{nonvar(Value), atom_codes(Value, Codes)}, characters(Codes).
value(Value) -->
{var(Value)}, characters(Codes), {atom_codes(Value, Codes)}.
characters([]) --> [].
characters([Code| Codes]) --> [Code], {character(Code)}, characters(Codes).
character(Code) :- Code @>= 0'a, Code @=< 0'z, !.
character(Code) :- Code @>= 0'A, Code @=< 0'Z.
:- end_object.