add cons patterns

interp.hs

@@ -13,6 +13,7 @@ data AST = Add AST AST
 
 data Pattern = VarP String
 			 | IntP Int
+			 | ConsP Pattern Pattern
 	 deriving (Show, Eq)
 
 data Value = IntV Int
@@ -68,11 +69,19 @@ eval (Call name args) = get >>= \m ->
 
 patternBindings :: Pattern -> Value -> Maybe Env
 patternBindings (VarP n) v = Just $ M.fromList [(n, v)]
+
 patternBindings (IntP n) (IntV v)
 	| v == n = Just M.empty
 	| otherwise = Nothing
 patternBindings (IntP n) _ = Nothing
 
+patternBindings (ConsP _ _) (ListV (_:[])) = Nothing
+patternBindings (ConsP xp xsp) (ListV (x:xs)) =
+	do
+		xe <- patternBindings xp x
+		xse <- patternBindings xsp $ ListV xs
+		Just $ M.union xe xse
+
 -- applies many arguments to a function
 applyMany :: Value -> [Value] -> InterpState Value
 applyMany fn@(FnV _) (arg:xs) =
@@ -118,4 +127,8 @@ main = do
 				 					(VarP "x", [IntConst 300])
 				 				  ],
 				 Call "f" [IntConst 2]]
-		prg4 = [ Def "lst" (ListConst [IntConst 1, IntConst 2, IntConst 3]) ]
+		prg4 = [ Def "lst" (ListConst [IntConst 1, IntConst 2, IntConst 3]),
+				 Def "f" $ Lambda [
+				 				(ConsP (VarP "x") (ConsP (VarP "y") (VarP "ys")), [Var "ys"])
+				 		   ],
+				 Call "f" [Var "lst"]]