toString (LexError e) = "Lexer error: " +++ e
instance + Error where
- (+) (Expected as) (Expected bs) = Expected (as++bs)
- (+) _ r = r
+ (+) (Expected as _) (Expected bs p) = Expected (as++bs) p
+ (+) _ r = r
runParser :: (Parser a b) [a] -> (Either Error b, [a])
runParser (Parser f) i = f i
(Right r, rest) = (Right r, rest)
(Left e2, rest) = (Left (e1+e2), rest)
-<?> :: (Parser a b) String -> Parser a b
-<?> p e = Parser \i -> case runParser p i of
- (Left e1, rest) = (Left (e1+(Expected [e])), rest)
+//Try the parser, if it fails decorate the error with Expected of the given String and position
+(<?>) :: (Parser a b) (String, Int) -> Parser a b
+(<?>) p (e,pos) = Parser \i -> case runParser p i of
+ (Left e1, rest) = let error = (e1+(Expected [e] pos)) in (Left error, rest)
(Right r, rest) = (Right r, rest)
fail :: Parser a b