implemented nth

src/Mtlstats/Util.hs

@@ -0,0 +1,29 @@
+{- |
+
+mtlstats
+Copyright (C) 2019 Rhéal Lamothe
+<rheal.lamothe@gmail.com>
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or (at
+your option) any later version.
+
+This program is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+-}
+
+module Mtlstats.Util (nth) where
+
+nth :: Int -> [a] -> Maybe a
+nth _ [] = Nothing
+nth n (x:xs)
+  | n == 0    = Just x
+  | n < 0     = Nothing
+  | otherwise = nth (pred n) xs