Choueka lang omega limit subset omega power
Automata.choueka_lang_omega_limit_subset_omega_power
Project documentation
The ω-limit of the Choueka language of M is a subset of the ω-power of the language of M. Note that this theorem does not need to assume that M is finite-state.
Exact Lean statement
theorem choueka_lang_omega_limit_subset_omega_power [Inhabited A] {M : DA A} {acc : Set M.State} :
(M.ChouekaLang acc)↗ω ⊆ (M.toNA.AcceptedLang acc)^ωFormal artifact
Lean source
theorem choueka_lang_omega_limit_subset_omega_power [Inhabited A] {M : DA A} {acc : Set M.State} : (M.ChouekaLang acc)↗ω ⊆ (M.toNA.AcceptedLang acc)^ω := by intro as ; simp [instOmegaLimit, OmegaLimit, frequently_iff_strict_mono] intro φ h_φ_mono h_prefix have h_m_ex : ∀ n, ∃ m, 0 < m ∧ m < φ n ∧ M.RunOn (as.extract 0 m) ∈ acc ∧ M.RunOn (as.extract m (φ n)) = M.RunOn (as.extract 0 (φ n)) ∧ ∀ k, m < k → k < φ n → M.RunOn (as.extract m k) ≠ M.RunOn (as.extract 0 k) := by intro n obtain ⟨m, h_m0, h_m1, h_acc, h_run, h_run'⟩ := h_prefix n simp [length_extract] at h_m1 simp [-List.extract_eq_drop_take, extract_extract2 (show m ≤ φ n by omega)] at h_acc simp [-List.extract_eq_drop_take, extract_extract1] at h_run use m ; simp [h_m0, h_m1, h_acc, h_run] intro k h_k h_k' specialize h_run' k h_k (by simp [length_extract, h_k']) simp [-List.extract_eq_drop_take, extract_extract2 (show k ≤ φ n by omega)] at h_run' exact h_run' choose φ' h_φ'_0 h_φ'_n h_acc h_run h_run' using h_m_ex have h_inj : Injective φ' := by intro n1 n2 h_φ' ; by_contra h_contra wlog h : n1 < n2 generalizing n1 n2 with h' · exact h' h_φ'.symm (by omega) (by omega) have := h_φ_mono h ; have := h_φ'_n n1 ; have := h_run n1 have := h_run' n2 (φ n1) (by omega) (by omega) simp_all obtain ⟨σ, h_σ_mono, h_φ_φ'⟩ := greater_subseq_lemma φ φ' h_inj use (fun k ↦ if k = 0 then 0 else φ' (σ (k - 1))) ; simp ; constructor · apply strictMono_nat_of_lt_succ ; intro n rcases (show n = 0 ∨ ¬ n = 0 by omega) with h_n | h_n <;> simp [h_n] · exact h_φ'_0 (σ 0) have := h_φ'_n (σ (n - 1)) have := h_φ_φ' (n - 1) grind · intro n simp [da_acc_lang_iff_run_acc] rcases (show n = 0 ∨ ¬ n = 0 by omega) with h_n | h_n <;> simp [h_n] · exact h_acc (σ 0) have h1 := h_φ'_n (σ (n - 1)) have h2 := h_φ_φ' (n - 1) ; simp [show n - 1 + 1 = n by omega] at h2 have h3 := append_extract_extract (xs := as) (show φ' (σ (n - 1)) ≤ φ (σ (n - 1)) by omega) (show φ (σ (n - 1)) ≤ φ' (σ n) by omega) have h4 := h_run (σ (n - 1)) ; simp [DA.RunOn] at h4 simp [← h3, DA.RunOn, da_run_from_on_append, h4] have h5 := append_extract_extract (xs := as) (show 0 ≤ φ (σ (n - 1)) by omega) (show φ (σ (n - 1)) ≤ φ' (σ n) by omega) simp [← da_run_from_on_append, h5] exact h_acc (σ n)- Project
- Automata Theory
- License
- Apache-2.0
- Commit
- f196548710ce
- Source
- AutomataTheory/Languages/ChouekaLemma.lean:57-103
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Related declarations
Acc lang congr
acc_lang_congr
Plain-language statement
The language accepted by c.toDA with a unique accepting state s is exactly the equivalence class of s.
Source project: Automata Theory
Person-level attribution pending.
Acc lang concat e
Automata.acc_lang_concat_e
Plain-language statement
The language of the concatenation NA that is accepted by M0's accepting states is the language accepted by M0.
Source project: Automata Theory
Person-level attribution pending.
Acc lang concat ne
Automata.acc_lang_concat_ne
Plain-language statement
The language of the concatenation NA that is accepted by M1's accepting states is the language accepted by M0 concatenated with the language accepted by M1 minus the empty word.
Source project: Automata Theory
Person-level attribution pending.