tasks a-s

Task/Catalan-numbers/Standard-ML/catalan-numbers.ml

@@ -0,0 +1,32 @@
+(*
+ * val catalan : int -> int
+ * Returns the nth Catalan number.
+ *)
+fun catalan 0 = 1
+|   catalan n = ((4 * n - 2) * catalan(n - 1)) div (n + 1);
+
+(*
+ * val print_catalans : int -> unit
+ * Prints out Catalan numbers 0 through 15.
+ *)
+fun print_catalans(n) =
+    if n > 15 then ()
+    else (print (Int.toString(catalan n) ^ "\n"); print_catalans(n + 1)); print_catalans(0);
+(*
+ * 1
+ * 1
+ * 2
+ * 5
+ * 14
+ * 42
+ * 132
+ * 429
+ * 1430
+ * 4862
+ * 16796
+ * 58786
+ * 208012
+ * 742900
+ * 2674440
+ * 9694845
+ *)