Logtalk 2.28.2 files.

git-svn-id: https://yap.svn.sf.net/svnroot/yap/trunk@1711 b08c6af1-5177-4d33-ba66-4b1c6b8b522a

Logtalk/examples/parametric/parametric.lgt

@@ -7,7 +7,70 @@
 
 
 
-/* The first two parametric objects represent time and date values as 
+/*	The first parametric object defines some useful predicates for working  
+	with lists.
+*/
+
+
+% dealing with non-empty lists is easy:
+
+:- object(.(_, _)).			% note that the [X, Y, ...] notation
+ 							% is just syntactic sugar for ./2
+	:- public(last/1).
+	:- mode(last(?term), zero_or_one).
+
+	:- public(member/1).
+	:- mode(member(?term), zero_or_more).
+
+	:- public(nextto/2).
+	:- mode(nextto(?term, ?term), zero_or_more).
+
+	last(Last) :-
+		this([Head| Tail]),
+		last(Tail, Head, Last).
+
+	last([], Last, Last).
+	last([Head| Tail], _, Last) :-
+		last(Tail, Head, Last).
+
+	member(Element) :-
+		this(List),
+		member(Element, List).
+
+	member(Element, [Element| _]).
+	member(Element, [_| Tail]) :-
+		member(Element, Tail).
+
+	nextto(X, Y) :-
+		this([Head| Tail]),
+		nextto(X, Y, [Head| Tail]).
+
+	nextto(X, Y, [X, Y| _]).
+	nextto(X, Y, [_| Tail]) :-
+		nextto(X, Y, Tail).
+
+:- end_object.
+
+
+% dealing with empty lists must also be done but it's a bit tricky:
+
+:- object([],				% the empty list is an atom, not a compound term, 
+	extends([.(_, _)])).	% so the "extends" relation would be always wrong
+
+	last(_) :-				% the trick is to redefine all inherited predicates
+		fail.				% to do the right thing for empty lists
+
+	member(_) :-
+		fail.
+
+	nextto(_, _) :-
+		fail.
+
+:- end_object.
+
+
+
+/*	The next two parametric objects represent time and date values as 
 	compound terms using the object's identifiers.
 */
 
@@ -143,7 +206,7 @@
 	updated object identifier.
 */
 
-:- object(rectangle(_width, _height, _x, _y)).
+:- object(rectangle(_Width, _Height, _X, _Y)).
 
 	:- info([
 		version is 1.0,