小编gui*_*ido的帖子

我尝试为 ADT 定义一个 show 实例，但收到错误Argument list lengths differ in declaration show。我怎样才能在不使用的情况下完成这项工作Generic？

data Route = Home | Users String | User Int | NotFound String

instance showRoute :: Show Route where
    show Home = "Home"
    show Users str = "Users"
    show User i = "User"
    show NotFound str = "404"