-- 字句解析

whiteSpaces :: String -> String
whiteSpaces ('\t':xs) = '\t':whiteSpaces xs
whiteSpaces (' ':xs) = ' ':whiteSpaces xs
whiteSpaces ('\\':'\n':xs) = '\\':'\n':whiteSpaces xs
whiteSpaces ('\n':xs) = '\n':whiteSpaces xs
whiteSpaces (x:xs) = ""

lexer :: String -> [String]
lexer [] = [[]]
lexer (x:[]) = [[x]]
lexer (x:xs) = [[x], xs]

