📅 最后修改于: 2022-03-11 14:48:33.944000 🧑 作者: Mango
onlyParenthesis :: String -> String
onlyParenthesis [] = []
onlyParenthesis (x:xs)
| x /= '(' && x /= ')' && x /= '[' && x /= ']' && x /= '{' && x /= '}'= onlyParenthesis xs
| otherwise = x : onlyParenthesis xs