Update examples

testsuite/objc/expression_parser/ArithmeticExpressionParser.hs

@@ -0,0 +1,30 @@
+module ArithmeticExpressionParser where
+
+import Text.ParserCombinators.Parsec
+import Text.ParserCombinators.Parsec.Expr
+
+resource :: String -> IO String
+resource text = do
+  parsedText <- mapM parseString (lines text)
+  return (unlines parsedText)
+
+parseString s = do
+  case (parse expr "" s) of
+    Left err -> return ("Error " ++ show err)
+    Right num -> return (show num)
+
+expr :: Parser Integer
+expr = buildExpressionParser table factor <?> "expression"
+
+table = [ [op "*" (*) AssocLeft, op "/" div AssocLeft]
+        , [op "+" (+) AssocLeft, op "-" (-) AssocLeft] ]
+  where
+    op s f assoc = Infix (do { string s; return f }) assoc
+
+factor = do { char '('; x <- expr; char ')'; return x }
+         <|> number
+         <?> "simple expression"
+
+number :: Parser Integer
+number = do { ds <- many1 digit; return (read ds) } <?> "number"
+