The following question came to my mind while reading the definition of a perfect set from Walter Rudin's Principles of Mathematical Analysis, 3rd Edition, Page 32, Section 2.18(h):
If the metric space is the set of all rational numbers $\mathbb Q$ (instead of $\mathbb R^1$ -- the set of all real numbers), then does $\mathbb Q$ constitute a perfect set?
In my understanding, the answer is "yes". Because $\mathbb Q$ is closed (since $\mathbb Q$ contains each of its limit points if the underlying metric space is $\mathbb Q$) and because every point of $\mathbb Q$ is a limit point of $\mathbb Q$ (arbitrary proximity). I'm not feeling so much sure somehow, and didn't find a corroboration elsewhere. Therefore this query.
Would appreciate help. Thanks.