Add Haskell template

templates/main.hs

@@ -0,0 +1,29 @@
+import System.Environment
+import System.Exit
+import System.IO
+import Data.Maybe
+
+type ChallengeReturn = String
+
+one :: String -> ChallengeReturn
+one inp = undefined
+
+two :: String -> ChallengeReturn
+two inp = undefined
+
+main :: IO ()
+main = do args <- getArgs
+          inp <- getContents
+          _runFn (_selectFn args) inp
+
+_selectFn :: [String] -> Maybe (String -> ChallengeReturn)
+_selectFn ["1"] = Just one
+_selectFn ["2"] = Just two
+_selectFn _ = Nothing
+
+_runFn :: Maybe (String -> ChallengeReturn) -> String -> IO ()
+_runFn Nothing _ = _debug "Missing or invalid day argument" >> exitWith (ExitFailure 1)
+_runFn (Just fn) inp = putStrLn (fn inp) >> exitWith ExitSuccess
+
+_debug :: String -> IO ()
+_debug x = do hPutStrLn stderr x