Data commit

Task/Nested-function/Haskell/nested-function-1.hs

@@ -0,0 +1,16 @@
+import Control.Monad.ST
+import Data.STRef
+
+makeList :: String -> String
+makeList separator = concat $ runST $ do
+  counter <- newSTRef 1
+  let makeItem item = do
+        x <- readSTRef counter
+        let result = show x ++ separator ++ item ++ "\n"
+        modifySTRef counter (+ 1)
+        return result
+  mapM makeItem ["first", "second", "third"]
+
+
+main :: IO ()
+main = putStr $ makeList ". "