相关疑难解决方法(0)

我正在学习哈斯克尔Write yourself a scheme.

我目前正在尝试char在计划中实施认可.char是#\<character>或#\<character-name>喜欢#\a或#\或#\space.

所以我写了下面的代码:

-- .. some code ..
data LispVal = Atom String
             | List [LispVal]
             | DottedList [LispVal] LispVal
             | String String
             | Number Integer
             | Bool Bool
             | Char Char deriving Show
-- .... More code ...
parseChar :: Parser LispVal
parseChar = liftM Char (parseSingleChar <|> parseSpecialCharNotation)

parseSingleChar :: Parser Char
parseSingleChar = do string "#\\"
                     x <- letter
                     return …