You can also have sets that are simultaneously closed and open. | Hacker News

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		GFK_of_xmaspast on Oct 15, 2014 \| parent \| context \| favorite \| on: Cryptic genetic variation in software: hunting a b... You can also have sets that are simultaneously closed and open.

monochromatic on Oct 15, 2014 [–]

Yep. For example, the empty set or the entire real number line.

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