Include Paulo Moura's Logtalk OO LP system

git-svn-id: https://yap.svn.sf.net/svnroot/yap/trunk@53 b08c6af1-5177-4d33-ba66-4b1c6b8b522a

Logtalk/examples/parametric/date3.lgt

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+
+:- object(date(_Year, _Month, _Day)).
+
+
+	:- info([
+		version is 1.0,
+		authors is 'Paulo Moura',
+		date is 1998/3/23,
+		comment is 'Dates as parametric objects.',
+		parnames is ['Year', 'Month', 'Day']]).
+
+
+	:- public(year/1).
+	:- mode(year(?integer), one).
+
+	:- public(month/1).
+	:- mode(month(?integer), one).
+
+	:- public(day/1).
+	:- mode(day(?integer), one).
+
+	:- public(today/0).
+	:- mode(today, one).
+
+	:- public(leap_year/0).
+	:- mode(leap_year, zero_or_one).
+
+
+	year(Year) :-
+		parameter(1, Year).
+
+
+	month(Month) :-
+		parameter(2, Month).
+
+
+	day(Day) :-
+		parameter(3, Day).
+
+
+	today :-
+		{lgt_current_date(Year, Month, Day)},
+		parameter(1, Year),
+		parameter(2, Month),
+		parameter(3, Day).
+
+
+	leap_year :-
+		parameter(1, Year),
+		(0 is mod(Year, 4),
+		 0 is mod(Year, 100)
+		 ;
+		 0 is mod(Year, 400)),
+		!.
+
+
+:- end_object.