June 2018 Update

Task/Longest-string-challenge/Haskell/longest-string-challenge.hs

@@ -0,0 +1,25 @@
+module Main where
+
+import           System.Environment
+
+cmp :: String -> String -> Ordering
+cmp [] []         = EQ
+cmp [] (_:_)      = LT
+cmp (_:_) []      = GT
+cmp (_:xs) (_:ys) = cmp xs ys
+
+longest :: String -> String
+longest = longest' "" "" . lines
+  where
+    longest' acc l []         = acc
+    longest' [] l (x:xs)      = longest' x x xs
+    longest' acc l (x:xs) = case cmp l x of
+                                   LT -> longest' x x xs
+                                   EQ -> longest' (acc ++ '\n':x) l xs
+                                   GT -> longest' acc l xs
+
+main :: IO ()
+main = do
+  (file:_) <- getArgs
+  contents <- readFile file
+  putStrLn $ longest contents