From the article, "Either the machine prints NPR@NPR@, or it never prints NPR@NPR@." This makes sense in that the machine has told itself never to print NPR@NP

From the article, "Either the machine prints NPR@NPR@, or it never prints NPR@NPR@." This makes sense in that the machine has told itself never to print NPR@NPR@ in the future. It would be like trying to verify someone doesn't know a secret by asking them about the secret they shouldn't know. Zero knowledge proofs come to mind. And that's probably a good description of my knowledge on this subject. edit: changed asterisks to @ because HN doesn't display asterisks.