Handling quoted read syntax

app/Main.hs

@@ -13,7 +13,7 @@ main = runInputT defaultSettings (loop $ [])
    where
         loop :: LispEnv -> InputT IO ()
         loop env = do
-            minput <- getInputLine " > "
+            minput <- getInputLine "> "
             case minput of
                 Nothing -> return ()
                 Just "exit" -> return ()

src/BasicParser.hs

@@ -1,7 +1,7 @@
 module BasicParser where
 
 import Control.Applicative ( Alternative(..) )
-import Data.Char ( isDigit, isNumber, isSpace )
+import Data.Char ( isDigit, isNumber, isSpace, isAlphaNum )
 import Text.Read ( readMaybe )
 
 data Parser a = Parser {
@@ -64,7 +64,7 @@ pString (x:xs) = do
 pString [] = pure ""
 
 pToken :: Parser String
-pToken = pUntil $ \x -> isSpace x || x == ')' || x == '('
+pToken = pUntil (not . isAlphaNum)
 
 pDigit :: Parser Char
 pDigit = pCharIf isDigit

src/LispParser.hs

@@ -4,6 +4,7 @@ import BasicParser
     ( Parser, pCharIf, pUntil, pInt, pFloat, tokenify, pToken, pString )
 import Expressions ( SExpr(..), Atom(..), Statement(..) )
 import Control.Applicative ( Alternative(some, (<|>)) )
+import Debug.Trace
 
 _pAtom :: Parser Atom
 _pAtom = AInt <$> pInt
@@ -28,9 +29,26 @@ pAtom = (pCharIf (== '\'') *> pQuotedAtom)
 --          but I believe that this is not really a feature.
 pQuotedAtom :: Parser Atom
 pQuotedAtom = ANil <$ pString "()"
-          <|> pCharIf (== '\'') *> ((\x -> ACons (ASymbol "quote") (ACons x ANil)) <$> pQuotedAtom)
+          <|> pCharIf (== '\'') *>
+                ((\x -> ACons (ASymbol "quote") (ACons x ANil)) <$> pQuotedAtom)
+          <|> pCharIf (== '(') *> pConsReadExpr <*pCharIf (== ')')
           <|> AQuote <$> _pAtom
 
+pConsReadExpr :: Parser Atom
+pConsReadExpr =
+    do
+        fs <- tokenify pQuotedAtom
+        se <- tokenify pConsReadExpr
+        return $ ACons fs se
+    <|> do
+        fs <- tokenify pQuotedAtom
+        tokenify $ pCharIf (== '.')
+        se <- tokenify pQuotedAtom
+        return $ ACons fs se
+    <|> do
+        fs <- tokenify pQuotedAtom
+        return $ ACons fs ANil
+
 pSExpr :: Parser SExpr
 pSExpr = pCharIf (== '(') *> (SExpr <$> some (tokenify pStatement)) <* pCharIf (== ')')