Dfa num state min
Language.dfa_num_state_min
Plain-language statement
All DFAs accepting l must have at least as many states as the number of equivalence classes of the Nerode congruence on l.
Exact Lean statement
theorem dfa_num_state_min {State : Type} {M : DA.FinAcc State α} [Finite State] :
Nat.card State ≥ Nat.card (language M).NerodeQuotientFormal artifact
Lean source
theorem dfa_num_state_min {State : Type} {M : DA.FinAcc State α} [Finite State] : Nat.card State ≥ Nat.card (language M).NerodeQuotient := by let ws : Set (List α) := Set.range (Quotient.out : NerodeQuotient (language M) → List α) have : Finite (language M).NerodeQuotient := IsRegular.iff_finite_nerodeQuotient.mp (IsRegular.iff_dfa.mpr ⟨State, inferInstance, M, rfl⟩) have : Finite ws := Set.finite_range _ |>.to_subtype have hws : ws.Pairwise (fun x y ↦ ¬((language M).NerodeCongruence).r x y) := by rintro _ ⟨qx, rfl⟩ _ ⟨qy, rfl⟩ hne h apply hne simpa using Quotient.sound h have h1 := dfa_num_state_ge hws rfl rw [Nat.card_congr (Equiv.ofInjective _ Quotient.out_injective).symm] at h1 assumption- Project
- Lean Computer Science Library
- License
- Apache-2.0
- Commit
- f36649cff2c9
- Source
- Cslib/Computability/Languages/MyhillNerode.lean:146-158
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Related declarations
Unique minimal
Cslib.Automata.DA.FinAcc.unique_minimal
Plain-language statement
The minimal DFA M accepting the language l is unique up to unique isomorphism.
Source project: Lean Computer Science Library
Person-level attribution pending.
Buchi Family cover
Cslib.Automata.NA.Buchi.buchiFamily_cover
Project documentation
na.buchiFamily is a cover if na has only finitely many states. This theorem uses the Ramsey theorem for infinite graphs and does not depend on any details of na.BuchiCongruence other than that it is of finite index.
Source project: Lean Computer Science Library
Person-level attribution pending.
Buchi Family saturation
Cslib.Automata.NA.Buchi.buchiFamily_saturation
Plain-language statement
na.buchiFamily saturates the ω-language accepted by na.
Source project: Lean Computer Science Library
Person-level attribution pending.