support for maybe types

Imp.ast

@@ -10,7 +10,7 @@ data Exp = SET ID Exp
     | IF SimpleExp Exp Exp  
     | WHILE SimpleExp Exp  
     | BEGIN (List1 Exp)
-    | TUPY (Exp, Exp)
+    | TUPY (Exp, Exp) (Maybe Potato)
     | LET [(String, Exp)] 
     
 data BinOp = Plus SimpleExp SimpleExp  

src/AST.hs

@@ -59,9 +59,18 @@ stypeToString :: StrictType -> (String, String)
 stypeToString (_, (ConT n)) = (showName n, "")
 stypeToString (_, (AppT ListT t)) = let (s, rs) = (stypeToString (IsStrict, t))
                                         in (s ++ "*", (rs ++ "\n\n" ++ makeMultiRules (AppT (ConT list0) t) s))
-stypeToString (_, (AppT (ConT n) t)) = let (s, rs) = (stypeToString (IsStrict, t))
-                                           c = if n == list0 then "*" else "+"
-                                       in (s ++ c, (rs ++ "\n\n" ++ makeMultiRules (AppT (ConT n) t) s))
+stypeToString (_, (AppT (ConT n) t)) = 
+    if n == list0 || n == list1 then 
+        let (s, rs) = (stypeToString (IsStrict, t))
+            c = if n == list0 then "*" else "+"
+        in (s ++ c, (rs ++ "\n\n" ++ makeMultiRules (AppT (ConT n) t) s))
+    else if n == (mkName "Maybe") then
+             let (s, rs) = (stypeToString (IsStrict, t))
+             in (("Maybe" ++ s), 
+                 rs ++ ("\n\nMaybe" ++ s ++ ": " ++ s ++ "\t{Just $1}\n" ++
+                                   (makeTab ("maybe" ++ s)) ++ "| \t{Nothing}"))
+    else ("", "")
+                                        
 stypeToString (_, (AppT t1 t2)) = let ts = flattenTuple t1 t2 
                                       ts' = map (stypeToString . (\x -> (IsStrict, x))) ts
                                       (s, rs) = ((foldr (\(x, y) a -> (fixMultis x) ++ "\\" ++ a) "" ts'),