Data commit

Task/Pascals-triangle/Logtalk/pascals-triangle.logtalk

@@ -0,0 +1,33 @@
+:- object(pascals).
+
+    :- uses(integer, [plus/3, succ/2]).
+
+    :- public(reset/0).
+
+    reset :-
+        retractall(triangle_(_,_,_)).
+
+    :- private(triangle_/3).
+    :- dynamic(triangle_/3).
+
+    :- public(triangle/2).
+
+    triangle(N, Lines) :-
+        triangle(N, _, DiffLines),
+        difflist::as_list(DiffLines, Lines).
+
+    % Shortcut with cached value if it exists.
+    triangle(N, Line, DiffLines) :- triangle_(N, Line, DiffLines), !.
+
+    triangle(N, Line, DiffLines) :-
+        succ(N0, N),
+        triangle(N0, Line0, DiffLines0),
+        ZL = [0|Line0],
+        list::append(Line0, [0], ZR),
+        meta::map(plus, ZL, ZR, Line),
+        difflist::add(Line, DiffLines0, DiffLines),
+        asserta(triangle_(N, Line, DiffLines)).
+
+    triangle(1, [1], [[1]|X]-X).
+
+:- end_object.