tracks/fsharp/exercises/pascals-triangle/Example.fs in trackler-2.2.1.49 vs tracks/fsharp/exercises/pascals-triangle/Example.fs in trackler-2.2.1.50

@@ -1,9 +1,13 @@
 module PascalsTriangle
-    
-let triangle rows = 
-    let row i = 
-        [1 .. i - 1] 
-        |> List.scan (fun acc j -> acc * (i - j) / j) 1 
-   
-    [1..rows] 
-    |> List.map row 
+
+let rows numberOfRows : int list list option = 
+    match numberOfRows with 
+    | r when r < 0 -> None
+    | _ ->
+        let row i = 
+            [1 .. i - 1] 
+            |> List.scan (fun acc j -> acc * (i - j) / j) 1 
+
+        [1..numberOfRows] 
+        |> List.map row
+        |> Some
\ No newline at end of file