September 2017 Update

Task/Substring/Haskell/substring-2.hs

@@ -0,0 +1,30 @@
+import qualified Data.Text as T
+       (Text, take, drop, init, breakOn, pack, unpack)
+
+fromNforM :: Int -> Int -> T.Text -> T.Text
+fromNforM n m s = T.take m (T.drop n s)
+
+fromNtoEnd :: Int -> T.Text -> T.Text
+fromNtoEnd = T.drop
+
+allButLast :: T.Text -> T.Text
+allButLast = T.init
+
+fromCharForM :: T.Text -> Int -> T.Text -> T.Text
+fromCharForM needle m haystack = T.take m $ snd (T.breakOn needle haystack)
+
+fromStringForM :: T.Text -> Int -> T.Text -> T.Text
+fromStringForM = fromCharForM
+
+-- TEST -----------------------------------------------------------------------
+main :: IO ()
+main =
+  mapM_
+    (putStrLn . T.unpack)
+    ([ fromNforM 9 10
+     , fromNtoEnd 20
+     , allButLast
+     , fromCharForM (T.pack "话") 6
+     , fromStringForM (T.pack "大势") 6
+     ] <*>
+     [T.pack "天地不仁仁者人也🐒话说天下大势分久必合🍑合久必分🔥"])