Initial data commit

Task/Left-factorials/Prolog/left-factorials.pro

@@ -0,0 +1,22 @@
+leftfact(N):-
+    leftfact(N, 0, 0, 1).
+
+leftfact(N, N, _, _):-
+    !.
+leftfact(N, M, L, F):-
+    ((M =< 10 ; (M =< 110, 0 is M mod 10)) ->
+        writef("!%w = %w\n", [M, L])
+        ;
+        (0 is M mod 1000 ->
+            number_string(L, S),
+            string_length(S, Len),
+            writef("length of !%w is %w\n", [M, Len])
+            ;
+            true)),
+    L1 is L + F,
+    M1 is M + 1,
+    F1 is F * M1,
+    leftfact(N, M1, L1, F1).
+
+main:-
+    leftfact(10001).