[SOLVED] Haskell Attoparsec infinite loop

Haskell Attoparsec infinite loop

The code is based on Haskell Attoparsec, and when I use parseOnly pString "v", it gives me the right answer as Right (DontNeedTrim, "v").

While when I use the instruction parseOnly (many' pString) "v", it seems drops into the infinite loop and finally failed with the overflowed stack.

data Signal = NeedTrim
              | DontNeedTrim
              deriving (Show)

pString :: Parser (Signal, [Char])
pString = ((char '\"' *> many' pChar' <* char '\"') >>= \s -> return (NeedTrim, s))
          <|> (many' pChar >>= \s -> return (DontNeedTrim, s))

pChar :: Parser Char
pChar = char '\\' *> (pEscape <|> spaces *> endOfLine *> pChar)
        <|> satisfy (`C.notElem` "\"\\\n#;")

pChar' :: Parser Char
pChar' = char '\\' *> pEscape
         <|> satisfy (`C.notElem` "\\\"")

pEscape :: Parser Char
pEscape = choice (zipWith decode "bnt\\\"" "\b\n\t\\\"")
  where decode c r = r <$ char c

Solution

The second alternative in pString accepts the empty string: many' pChar >>= \s -> return (...). Thus many' pString keeps consuming the empty string ad infinitum.