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DcoBA · co-Büchi ω-regular

Eventually always b

@thethinkmachine·version 1·CC BY 4.0·added 28 Sept 2026

FG b as a deterministic co-Büchi automaton — the same language a Büchi automaton can only recognise by guessing. Swapping α from Büchi to co-Büchi is the entire difference.

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last was…last was…baab
The machine as drawn — 2 states, 4 transitions.

The author’s examples, run

(b) → accepta(b) → acceptab(b) → acceptaaaa(b) → accept(a) → reject(ab) → rejectbbb(ab) → reject