Family Day update

Task/S-Expressions/Haskell/s-expressions.hs

@@ -1,28 +1,40 @@
-import Data.Functor
-import Text.Parsec ((<|>), (<?>), many, many1, char, try, parse, sepBy, choice, between)
+import qualified Data.Functor.Identity as F
+import qualified Text.Parsec.Prim as Prim
+import Text.Parsec
+       ((<|>), (<?>), many, many1, char, try, parse, sepBy, choice,
+        between)
+import Text.Parsec.Token
+       (integer, float, whiteSpace, stringLiteral, makeTokenParser)
 import Text.Parsec.Char (noneOf)
-import Text.Parsec.Token (integer, float, whiteSpace, stringLiteral, makeTokenParser)
 import Text.Parsec.Language (haskell)
 
-data Val = Int Integer
-         | Float Double
-         | String String
-         | Symbol String
-         | List [Val] deriving (Eq, Show)
+data Val
+  = Int Integer
+  | Float Double
+  | String String
+  | Symbol String
+  | List [Val]
+  deriving (Eq, Show)
 
+tProg :: Prim.ParsecT String a F.Identity [Val]
 tProg = many tExpr <?> "program"
-  where tExpr = between ws ws (tList <|> tAtom) <?> "expression"
-        ws = whiteSpace haskell
-        tAtom  =  (try (Float <$> float haskell) <?> "floating point number")
-              <|> (try (Int <$> integer haskell) <?> "integer")
-              <|> (String <$> stringLiteral haskell <?> "string")
-              <|> (Symbol <$> many1 (noneOf "()\"\t\n\r ") <?> "symbol")
-              <?> "atomic expression"
-        tList = List <$> between (char '(') (char ')') (many tExpr) <?> "list"
+  where
+    tExpr = between ws ws (tList <|> tAtom) <?> "expression"
+    ws = whiteSpace haskell
+    tAtom =
+      (try (Float <$> float haskell) <?> "floating point number") <|>
+      (try (Int <$> integer haskell) <?> "integer") <|>
+      (String <$> stringLiteral haskell <?> "string") <|>
+      (Symbol <$> many1 (noneOf "()\"\t\n\r ") <?> "symbol") <?>
+      "atomic expression"
+    tList = List <$> between (char '(') (char ')') (many tExpr) <?> "list"
 
+p :: String -> IO ()
 p = either print (putStrLn . unwords . map show) . parse tProg ""
 
+main :: IO ()
 main = do
-    let expr = "((data \"quoted data\" 123 4.5)\n  (data (!@# (4.5) \"(more\" \"data)\")))"
-    putStrLn ("The input:\n" ++ expr ++ "\nParsed as:")
-    p expr
+  let expr =
+        "((data \"quoted data\" 123 4.5)\n  (data (!@# (4.5) \"(more\" \"data)\")))"
+  putStrLn ("The input:\n" ++ expr ++ "\n\nParsed as:")
+  p expr