feat(MultiTapeTM): Some lemmas about Turing machine tapes - #768
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crei
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Aug 1, 2026
| If the Turing machine halts, it will stay at the halting configuration. -/ | ||
| def configs (cfg : Cfg k Symbol State input) (t : ℕ) : Cfg k Symbol State input := tm.step^[t] cfg | ||
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| /-- Any number of steps run from a halting configuration results in the same configuration. -/ |
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Initially, I thought proofs should always first turn configs into step^[n] and then use the Function.iterate_* lemmas, but I think it's better to not unfold configs and add these lemmas here instead.
SamuelSchlesinger
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Aug 2, 2026
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This looks good to me. If you want to improve before merging, add docs to the lemmata that currently don't have doctext. Otherwise its fine to do as a followup.
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@fmontesi please merge when you get the chance. |
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Some useful lemmas about how the tapes are modified during the execution of Turing machines, some lemmas about halting behaviour and some about space usage (partly just moved).
This has been split out from #767