September Morn Update

Task/Permutations/Haskell/permutations-5.hs

@@ -0,0 +1,10 @@
+permutations :: [a] -> [[a]]
+permutations =
+  foldr (\x ac -> ac >>= (fmap . ins x) <*> (enumFromTo 0 . length)) [[]]
+  where
+    ins x xs n =
+      let (a, b) = splitAt n xs
+      in a ++ x : b
+
+main :: IO ()
+main = print $ permutations [1, 2, 3]