Initial data commit

Task/Forward-difference/Picat/forward-difference.picat

@@ -0,0 +1,31 @@
+go =>
+   L = [90, 47, 58, 29, 22, 32, 55, 5, 55, 73],
+   foreach(I in 1..L.length-1)
+      println([d=I,diffi(L,I)])
+   end,
+   nl,
+   % All differences (a sublist to save space)
+   println(alldiffs(L[1..6])),
+   nl.
+
+% Difference of the list
+diff(L) = Diff =>
+   Diff = [L[I]-L[I-1] : I in 2..L.length].
+
+% The i'th list difference
+diffi(L,D) = Diff =>
+   Diff1 = L,
+   foreach(_I in 1..D)
+      Diff1 := diff(Diff1)
+   end,
+   Diff = Diff1.
+
+% all differences
+alldiffs(L) = Diffs =>
+   Diffs1 = [],
+   Diff = L,
+   foreach(_I in 1..L.length-1)
+      Diff := diff(Diff),
+      Diffs1 := Diffs1 ++ [Diff]
+   end,
+   Diffs = Diffs1.