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Theorem wrd2ind 13679

Description: Perform induction over the structure of two words of the same length. (Contributed by AV, 23-Jan-2019.)

**Hypotheses**
Ref	Expression
wrd2ind.1	⊢ ((𝑥 = ∅ ∧ 𝑤 = ∅) → (𝜑 ↔ 𝜓))
wrd2ind.2	⊢ ((𝑥 = 𝑦 ∧ 𝑤 = 𝑢) → (𝜑 ↔ 𝜒))
wrd2ind.3	⊢ ((𝑥 = (𝑦 ++ ⟨“𝑧”⟩) ∧ 𝑤 = (𝑢 ++ ⟨“𝑠”⟩)) → (𝜑 ↔ 𝜃))
wrd2ind.4	⊢ (𝑥 = 𝐴 → (𝜌 ↔ 𝜏))
wrd2ind.5	⊢ (𝑤 = 𝐵 → (𝜑 ↔ 𝜌))
wrd2ind.6	⊢ 𝜓
wrd2ind.7	⊢ (((𝑦 ∈ Word 𝑋 ∧ 𝑧 ∈ 𝑋) ∧ (𝑢 ∈ Word 𝑌 ∧ 𝑠 ∈ 𝑌) ∧ (♯‘𝑦) = (♯‘𝑢)) → (𝜒 → 𝜃))

**Assertion**
Ref	Expression
wrd2ind	⊢ ((𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ Word 𝑌 ∧ (♯‘𝐴) = (♯‘𝐵)) → 𝜏)

Distinct variable groups: 𝑥,𝑤,𝐴 𝑦,𝑤,𝑧,𝐵,𝑥 𝑢,𝑠,𝑤,𝑥,𝑦,𝑧,𝑋 𝑌,𝑠,𝑢,𝑤,𝑥,𝑦,𝑧 𝜒,𝑤,𝑥 𝜑,𝑠,𝑢,𝑦,𝑧 𝜏,𝑥 𝜃,𝑤,𝑥 𝜌,𝑤 Allowed substitution hints: 𝜑(𝑥,𝑤) 𝜓(𝑥,𝑦,𝑧,𝑤,𝑢,𝑠) 𝜒(𝑦,𝑧,𝑢,𝑠) 𝜃(𝑦,𝑧,𝑢,𝑠) 𝜏(𝑦,𝑧,𝑤,𝑢,𝑠) 𝜌(𝑥,𝑦,𝑧,𝑢,𝑠) 𝐴(𝑦,𝑧,𝑢,𝑠) 𝐵(𝑢,𝑠)

Proof of Theorem wrd2ind Dummy variables 𝑛 𝑚 are mutually distinct and distinct from all other variables.

Step	Hyp	Ref	Expression
1		lencl 13513	. . . . 5 ⊢ (𝐴 ∈ Word 𝑋 → (♯‘𝐴) ∈ ℕ₀)
2		eqeq2 2782	. . . . . . . . 9 ⊢ (𝑛 = 0 → ((♯‘𝑥) = 𝑛 ↔ (♯‘𝑥) = 0))
3	2	anbi2d 614	. . . . . . . 8 ⊢ (𝑛 = 0 → (((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = 𝑛) ↔ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = 0)))
4	3	imbi1d 330	. . . . . . 7 ⊢ (𝑛 = 0 → ((((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = 𝑛) → 𝜑) ↔ (((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = 0) → 𝜑)))
5	4	2ralbidv 3138	. . . . . 6 ⊢ (𝑛 = 0 → (∀𝑤 ∈ Word 𝑌∀𝑥 ∈ Word 𝑋(((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = 𝑛) → 𝜑) ↔ ∀𝑤 ∈ Word 𝑌∀𝑥 ∈ Word 𝑋(((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = 0) → 𝜑)))
6		eqeq2 2782	. . . . . . . . 9 ⊢ (𝑛 = 𝑚 → ((♯‘𝑥) = 𝑛 ↔ (♯‘𝑥) = 𝑚))
7	6	anbi2d 614	. . . . . . . 8 ⊢ (𝑛 = 𝑚 → (((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = 𝑛) ↔ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = 𝑚)))
8	7	imbi1d 330	. . . . . . 7 ⊢ (𝑛 = 𝑚 → ((((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = 𝑛) → 𝜑) ↔ (((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = 𝑚) → 𝜑)))
9	8	2ralbidv 3138	. . . . . 6 ⊢ (𝑛 = 𝑚 → (∀𝑤 ∈ Word 𝑌∀𝑥 ∈ Word 𝑋(((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = 𝑛) → 𝜑) ↔ ∀𝑤 ∈ Word 𝑌∀𝑥 ∈ Word 𝑋(((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = 𝑚) → 𝜑)))
10		eqeq2 2782	. . . . . . . . 9 ⊢ (𝑛 = (𝑚 + 1) → ((♯‘𝑥) = 𝑛 ↔ (♯‘𝑥) = (𝑚 + 1)))
11	10	anbi2d 614	. . . . . . . 8 ⊢ (𝑛 = (𝑚 + 1) → (((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = 𝑛) ↔ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1))))
12	11	imbi1d 330	. . . . . . 7 ⊢ (𝑛 = (𝑚 + 1) → ((((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = 𝑛) → 𝜑) ↔ (((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)) → 𝜑)))
13	12	2ralbidv 3138	. . . . . 6 ⊢ (𝑛 = (𝑚 + 1) → (∀𝑤 ∈ Word 𝑌∀𝑥 ∈ Word 𝑋(((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = 𝑛) → 𝜑) ↔ ∀𝑤 ∈ Word 𝑌∀𝑥 ∈ Word 𝑋(((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)) → 𝜑)))
14		eqeq2 2782	. . . . . . . . 9 ⊢ (𝑛 = (♯‘𝐴) → ((♯‘𝑥) = 𝑛 ↔ (♯‘𝑥) = (♯‘𝐴)))
15	14	anbi2d 614	. . . . . . . 8 ⊢ (𝑛 = (♯‘𝐴) → (((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = 𝑛) ↔ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (♯‘𝐴))))
16	15	imbi1d 330	. . . . . . 7 ⊢ (𝑛 = (♯‘𝐴) → ((((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = 𝑛) → 𝜑) ↔ (((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (♯‘𝐴)) → 𝜑)))
17	16	2ralbidv 3138	. . . . . 6 ⊢ (𝑛 = (♯‘𝐴) → (∀𝑤 ∈ Word 𝑌∀𝑥 ∈ Word 𝑋(((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = 𝑛) → 𝜑) ↔ ∀𝑤 ∈ Word 𝑌∀𝑥 ∈ Word 𝑋(((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (♯‘𝐴)) → 𝜑)))
18		eqeq1 2775	. . . . . . . . . . . 12 ⊢ ((♯‘𝑥) = 0 → ((♯‘𝑥) = (♯‘𝑤) ↔ 0 = (♯‘𝑤)))
19	18	adantl 467	. . . . . . . . . . 11 ⊢ (((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ (♯‘𝑥) = 0) → ((♯‘𝑥) = (♯‘𝑤) ↔ 0 = (♯‘𝑤)))
20		eqcom 2778	. . . . . . . . . . . . . . 15 ⊢ (0 = (♯‘𝑤) ↔ (♯‘𝑤) = 0)
21		hasheq0 13349	. . . . . . . . . . . . . . 15 ⊢ (𝑤 ∈ Word 𝑌 → ((♯‘𝑤) = 0 ↔ 𝑤 = ∅))
22	20, 21	syl5bb 272	. . . . . . . . . . . . . 14 ⊢ (𝑤 ∈ Word 𝑌 → (0 = (♯‘𝑤) ↔ 𝑤 = ∅))
23		hasheq0 13349	. . . . . . . . . . . . . . . 16 ⊢ (𝑥 ∈ Word 𝑋 → ((♯‘𝑥) = 0 ↔ 𝑥 = ∅))
24		wrd2ind.6	. . . . . . . . . . . . . . . . . 18 ⊢ 𝜓
25		wrd2ind.1	. . . . . . . . . . . . . . . . . 18 ⊢ ((𝑥 = ∅ ∧ 𝑤 = ∅) → (𝜑 ↔ 𝜓))
26	24, 25	mpbiri 248	. . . . . . . . . . . . . . . . 17 ⊢ ((𝑥 = ∅ ∧ 𝑤 = ∅) → 𝜑)
27	26	ex 397	. . . . . . . . . . . . . . . 16 ⊢ (𝑥 = ∅ → (𝑤 = ∅ → 𝜑))
28	23, 27	syl6bi 243	. . . . . . . . . . . . . . 15 ⊢ (𝑥 ∈ Word 𝑋 → ((♯‘𝑥) = 0 → (𝑤 = ∅ → 𝜑)))
29	28	com13 88	. . . . . . . . . . . . . 14 ⊢ (𝑤 = ∅ → ((♯‘𝑥) = 0 → (𝑥 ∈ Word 𝑋 → 𝜑)))
30	22, 29	syl6bi 243	. . . . . . . . . . . . 13 ⊢ (𝑤 ∈ Word 𝑌 → (0 = (♯‘𝑤) → ((♯‘𝑥) = 0 → (𝑥 ∈ Word 𝑋 → 𝜑))))
31	30	com24 95	. . . . . . . . . . . 12 ⊢ (𝑤 ∈ Word 𝑌 → (𝑥 ∈ Word 𝑋 → ((♯‘𝑥) = 0 → (0 = (♯‘𝑤) → 𝜑))))
32	31	imp31 404	. . . . . . . . . . 11 ⊢ (((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ (♯‘𝑥) = 0) → (0 = (♯‘𝑤) → 𝜑))
33	19, 32	sylbid 230	. . . . . . . . . 10 ⊢ (((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ (♯‘𝑥) = 0) → ((♯‘𝑥) = (♯‘𝑤) → 𝜑))
34	33	ex 397	. . . . . . . . 9 ⊢ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) → ((♯‘𝑥) = 0 → ((♯‘𝑥) = (♯‘𝑤) → 𝜑)))
35	34	com23 86	. . . . . . . 8 ⊢ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) → ((♯‘𝑥) = (♯‘𝑤) → ((♯‘𝑥) = 0 → 𝜑)))
36	35	impd 396	. . . . . . 7 ⊢ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) → (((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = 0) → 𝜑))
37	36	rgen2 3124	. . . . . 6 ⊢ ∀𝑤 ∈ Word 𝑌∀𝑥 ∈ Word 𝑋(((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = 0) → 𝜑)
38		fveq2 6330	. . . . . . . . . . . . 13 ⊢ (𝑥 = 𝑦 → (♯‘𝑥) = (♯‘𝑦))
39		fveq2 6330	. . . . . . . . . . . . 13 ⊢ (𝑤 = 𝑢 → (♯‘𝑤) = (♯‘𝑢))
40	38, 39	eqeqan12d 2787	. . . . . . . . . . . 12 ⊢ ((𝑥 = 𝑦 ∧ 𝑤 = 𝑢) → ((♯‘𝑥) = (♯‘𝑤) ↔ (♯‘𝑦) = (♯‘𝑢)))
41	38	eqeq1d 2773	. . . . . . . . . . . . 13 ⊢ (𝑥 = 𝑦 → ((♯‘𝑥) = 𝑚 ↔ (♯‘𝑦) = 𝑚))
42	41	adantr 466	. . . . . . . . . . . 12 ⊢ ((𝑥 = 𝑦 ∧ 𝑤 = 𝑢) → ((♯‘𝑥) = 𝑚 ↔ (♯‘𝑦) = 𝑚))
43	40, 42	anbi12d 616	. . . . . . . . . . 11 ⊢ ((𝑥 = 𝑦 ∧ 𝑤 = 𝑢) → (((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = 𝑚) ↔ ((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚)))
44		wrd2ind.2	. . . . . . . . . . 11 ⊢ ((𝑥 = 𝑦 ∧ 𝑤 = 𝑢) → (𝜑 ↔ 𝜒))
45	43, 44	imbi12d 333	. . . . . . . . . 10 ⊢ ((𝑥 = 𝑦 ∧ 𝑤 = 𝑢) → ((((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = 𝑚) → 𝜑) ↔ (((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)))
46	45	ancoms 446	. . . . . . . . 9 ⊢ ((𝑤 = 𝑢 ∧ 𝑥 = 𝑦) → ((((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = 𝑚) → 𝜑) ↔ (((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)))
47	46	cbvraldva 3326	. . . . . . . 8 ⊢ (𝑤 = 𝑢 → (∀𝑥 ∈ Word 𝑋(((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = 𝑚) → 𝜑) ↔ ∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)))
48	47	cbvralv 3320	. . . . . . 7 ⊢ (∀𝑤 ∈ Word 𝑌∀𝑥 ∈ Word 𝑋(((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = 𝑚) → 𝜑) ↔ ∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒))
49		swrdcl 13620	. . . . . . . . . . . . . . . . 17 ⊢ (𝑤 ∈ Word 𝑌 → (𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ∈ Word 𝑌)
50	49	adantr 466	. . . . . . . . . . . . . . . 16 ⊢ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) → (𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ∈ Word 𝑌)
51	50	ad2antrl 707	. . . . . . . . . . . . . . 15 ⊢ ((𝑚 ∈ ℕ₀ ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → (𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ∈ Word 𝑌)
52		simprll 764	. . . . . . . . . . . . . . . 16 ⊢ ((𝑚 ∈ ℕ₀ ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → 𝑤 ∈ Word 𝑌)
53		eqeq1 2775	. . . . . . . . . . . . . . . . . . . . . 22 ⊢ ((♯‘𝑥) = (𝑚 + 1) → ((♯‘𝑥) = (♯‘𝑤) ↔ (𝑚 + 1) = (♯‘𝑤)))
54		nn0p1nn 11532	. . . . . . . . . . . . . . . . . . . . . . 23 ⊢ (𝑚 ∈ ℕ₀ → (𝑚 + 1) ∈ ℕ)
55		eleq1 2838	. . . . . . . . . . . . . . . . . . . . . . . 24 ⊢ ((♯‘𝑤) = (𝑚 + 1) → ((♯‘𝑤) ∈ ℕ ↔ (𝑚 + 1) ∈ ℕ))
56	55	eqcoms 2779	. . . . . . . . . . . . . . . . . . . . . . 23 ⊢ ((𝑚 + 1) = (♯‘𝑤) → ((♯‘𝑤) ∈ ℕ ↔ (𝑚 + 1) ∈ ℕ))
57	54, 56	syl5ibr 236	. . . . . . . . . . . . . . . . . . . . . 22 ⊢ ((𝑚 + 1) = (♯‘𝑤) → (𝑚 ∈ ℕ₀ → (♯‘𝑤) ∈ ℕ))
58	53, 57	syl6bi 243	. . . . . . . . . . . . . . . . . . . . 21 ⊢ ((♯‘𝑥) = (𝑚 + 1) → ((♯‘𝑥) = (♯‘𝑤) → (𝑚 ∈ ℕ₀ → (♯‘𝑤) ∈ ℕ)))
59	58	impcom 394	. . . . . . . . . . . . . . . . . . . 20 ⊢ (((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)) → (𝑚 ∈ ℕ₀ → (♯‘𝑤) ∈ ℕ))
60	59	adantl 467	. . . . . . . . . . . . . . . . . . 19 ⊢ (((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1))) → (𝑚 ∈ ℕ₀ → (♯‘𝑤) ∈ ℕ))
61	60	impcom 394	. . . . . . . . . . . . . . . . . 18 ⊢ ((𝑚 ∈ ℕ₀ ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → (♯‘𝑤) ∈ ℕ)
62	61	nnge1d 11263	. . . . . . . . . . . . . . . . 17 ⊢ ((𝑚 ∈ ℕ₀ ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → 1 ≤ (♯‘𝑤))
63		wrdlenge1n0 13529	. . . . . . . . . . . . . . . . . 18 ⊢ (𝑤 ∈ Word 𝑌 → (𝑤 ≠ ∅ ↔ 1 ≤ (♯‘𝑤)))
64	52, 63	syl 17	. . . . . . . . . . . . . . . . 17 ⊢ ((𝑚 ∈ ℕ₀ ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → (𝑤 ≠ ∅ ↔ 1 ≤ (♯‘𝑤)))
65	62, 64	mpbird 247	. . . . . . . . . . . . . . . 16 ⊢ ((𝑚 ∈ ℕ₀ ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → 𝑤 ≠ ∅)
66		lswcl 13545	. . . . . . . . . . . . . . . 16 ⊢ ((𝑤 ∈ Word 𝑌 ∧ 𝑤 ≠ ∅) → (lastS‘𝑤) ∈ 𝑌)
67	52, 65, 66	syl2anc 573	. . . . . . . . . . . . . . 15 ⊢ ((𝑚 ∈ ℕ₀ ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → (lastS‘𝑤) ∈ 𝑌)
68	51, 67	jca 501	. . . . . . . . . . . . . 14 ⊢ ((𝑚 ∈ ℕ₀ ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → ((𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ∈ Word 𝑌 ∧ (lastS‘𝑤) ∈ 𝑌))
69		swrdcl 13620	. . . . . . . . . . . . . . . 16 ⊢ (𝑥 ∈ Word 𝑋 → (𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) ∈ Word 𝑋)
70	69	adantl 467	. . . . . . . . . . . . . . 15 ⊢ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) → (𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) ∈ Word 𝑋)
71	70	ad2antrl 707	. . . . . . . . . . . . . 14 ⊢ ((𝑚 ∈ ℕ₀ ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → (𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) ∈ Word 𝑋)
72		simprlr 765	. . . . . . . . . . . . . . 15 ⊢ ((𝑚 ∈ ℕ₀ ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → 𝑥 ∈ Word 𝑋)
73		eleq1 2838	. . . . . . . . . . . . . . . . . . . 20 ⊢ ((♯‘𝑥) = (𝑚 + 1) → ((♯‘𝑥) ∈ ℕ ↔ (𝑚 + 1) ∈ ℕ))
74	54, 73	syl5ibr 236	. . . . . . . . . . . . . . . . . . 19 ⊢ ((♯‘𝑥) = (𝑚 + 1) → (𝑚 ∈ ℕ₀ → (♯‘𝑥) ∈ ℕ))
75	74	ad2antll 708	. . . . . . . . . . . . . . . . . 18 ⊢ (((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1))) → (𝑚 ∈ ℕ₀ → (♯‘𝑥) ∈ ℕ))
76	75	impcom 394	. . . . . . . . . . . . . . . . 17 ⊢ ((𝑚 ∈ ℕ₀ ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → (♯‘𝑥) ∈ ℕ)
77	76	nnge1d 11263	. . . . . . . . . . . . . . . 16 ⊢ ((𝑚 ∈ ℕ₀ ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → 1 ≤ (♯‘𝑥))
78		wrdlenge1n0 13529	. . . . . . . . . . . . . . . . 17 ⊢ (𝑥 ∈ Word 𝑋 → (𝑥 ≠ ∅ ↔ 1 ≤ (♯‘𝑥)))
79	72, 78	syl 17	. . . . . . . . . . . . . . . 16 ⊢ ((𝑚 ∈ ℕ₀ ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → (𝑥 ≠ ∅ ↔ 1 ≤ (♯‘𝑥)))
80	77, 79	mpbird 247	. . . . . . . . . . . . . . 15 ⊢ ((𝑚 ∈ ℕ₀ ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → 𝑥 ≠ ∅)
81		lswcl 13545	. . . . . . . . . . . . . . 15 ⊢ ((𝑥 ∈ Word 𝑋 ∧ 𝑥 ≠ ∅) → (lastS‘𝑥) ∈ 𝑋)
82	72, 80, 81	syl2anc 573	. . . . . . . . . . . . . 14 ⊢ ((𝑚 ∈ ℕ₀ ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → (lastS‘𝑥) ∈ 𝑋)
83	68, 71, 82	jca32 505	. . . . . . . . . . . . 13 ⊢ ((𝑚 ∈ ℕ₀ ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → (((𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ∈ Word 𝑌 ∧ (lastS‘𝑤) ∈ 𝑌) ∧ ((𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) ∈ Word 𝑋 ∧ (lastS‘𝑥) ∈ 𝑋)))
84	83	adantlr 694	. . . . . . . . . . . 12 ⊢ (((𝑚 ∈ ℕ₀ ∧ ∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)) ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → (((𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ∈ Word 𝑌 ∧ (lastS‘𝑤) ∈ 𝑌) ∧ ((𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) ∈ Word 𝑋 ∧ (lastS‘𝑥) ∈ 𝑋)))
85		simprl 754	. . . . . . . . . . . . . 14 ⊢ (((𝑚 ∈ ℕ₀ ∧ ∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)) ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → (𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋))
86		simplr 752	. . . . . . . . . . . . . 14 ⊢ (((𝑚 ∈ ℕ₀ ∧ ∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)) ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → ∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒))
87		simprrl 766	. . . . . . . . . . . . . . . . 17 ⊢ (((𝑚 ∈ ℕ₀ ∧ ∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)) ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → (♯‘𝑥) = (♯‘𝑤))
88	87	oveq1d 6806	. . . . . . . . . . . . . . . 16 ⊢ (((𝑚 ∈ ℕ₀ ∧ ∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)) ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → ((♯‘𝑥) − 1) = ((♯‘𝑤) − 1))
89		simprlr 765	. . . . . . . . . . . . . . . . 17 ⊢ (((𝑚 ∈ ℕ₀ ∧ ∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)) ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → 𝑥 ∈ Word 𝑋)
90		fzossfz 12689	. . . . . . . . . . . . . . . . . 18 ⊢ (0..^(♯‘𝑥)) ⊆ (0...(♯‘𝑥))
91		simprrr 767	. . . . . . . . . . . . . . . . . . . 20 ⊢ (((𝑚 ∈ ℕ₀ ∧ ∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)) ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → (♯‘𝑥) = (𝑚 + 1))
92	54	ad2antrr 705	. . . . . . . . . . . . . . . . . . . 20 ⊢ (((𝑚 ∈ ℕ₀ ∧ ∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)) ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → (𝑚 + 1) ∈ ℕ)
93	91, 92	eqeltrd 2850	. . . . . . . . . . . . . . . . . . 19 ⊢ (((𝑚 ∈ ℕ₀ ∧ ∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)) ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → (♯‘𝑥) ∈ ℕ)
94		fzo0end 12761	. . . . . . . . . . . . . . . . . . 19 ⊢ ((♯‘𝑥) ∈ ℕ → ((♯‘𝑥) − 1) ∈ (0..^(♯‘𝑥)))
95	93, 94	syl 17	. . . . . . . . . . . . . . . . . 18 ⊢ (((𝑚 ∈ ℕ₀ ∧ ∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)) ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → ((♯‘𝑥) − 1) ∈ (0..^(♯‘𝑥)))
96	90, 95	sseldi 3750	. . . . . . . . . . . . . . . . 17 ⊢ (((𝑚 ∈ ℕ₀ ∧ ∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)) ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → ((♯‘𝑥) − 1) ∈ (0...(♯‘𝑥)))
97		swrd0len 13623	. . . . . . . . . . . . . . . . 17 ⊢ ((𝑥 ∈ Word 𝑋 ∧ ((♯‘𝑥) − 1) ∈ (0...(♯‘𝑥))) → (♯‘(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩)) = ((♯‘𝑥) − 1))
98	89, 96, 97	syl2anc 573	. . . . . . . . . . . . . . . 16 ⊢ (((𝑚 ∈ ℕ₀ ∧ ∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)) ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → (♯‘(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩)) = ((♯‘𝑥) − 1))
99		simprll 764	. . . . . . . . . . . . . . . . 17 ⊢ (((𝑚 ∈ ℕ₀ ∧ ∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)) ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → 𝑤 ∈ Word 𝑌)
100		oveq1 6798	. . . . . . . . . . . . . . . . . . . . . 22 ⊢ ((♯‘𝑤) = (♯‘𝑥) → ((♯‘𝑤) − 1) = ((♯‘𝑥) − 1))
101		oveq2 6799	. . . . . . . . . . . . . . . . . . . . . 22 ⊢ ((♯‘𝑤) = (♯‘𝑥) → (0...(♯‘𝑤)) = (0...(♯‘𝑥)))
102	100, 101	eleq12d 2844	. . . . . . . . . . . . . . . . . . . . 21 ⊢ ((♯‘𝑤) = (♯‘𝑥) → (((♯‘𝑤) − 1) ∈ (0...(♯‘𝑤)) ↔ ((♯‘𝑥) − 1) ∈ (0...(♯‘𝑥))))
103	102	eqcoms 2779	. . . . . . . . . . . . . . . . . . . 20 ⊢ ((♯‘𝑥) = (♯‘𝑤) → (((♯‘𝑤) − 1) ∈ (0...(♯‘𝑤)) ↔ ((♯‘𝑥) − 1) ∈ (0...(♯‘𝑥))))
104	103	adantr 466	. . . . . . . . . . . . . . . . . . 19 ⊢ (((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)) → (((♯‘𝑤) − 1) ∈ (0...(♯‘𝑤)) ↔ ((♯‘𝑥) − 1) ∈ (0...(♯‘𝑥))))
105	104	ad2antll 708	. . . . . . . . . . . . . . . . . 18 ⊢ (((𝑚 ∈ ℕ₀ ∧ ∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)) ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → (((♯‘𝑤) − 1) ∈ (0...(♯‘𝑤)) ↔ ((♯‘𝑥) − 1) ∈ (0...(♯‘𝑥))))
106	96, 105	mpbird 247	. . . . . . . . . . . . . . . . 17 ⊢ (((𝑚 ∈ ℕ₀ ∧ ∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)) ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → ((♯‘𝑤) − 1) ∈ (0...(♯‘𝑤)))
107		swrd0len 13623	. . . . . . . . . . . . . . . . 17 ⊢ ((𝑤 ∈ Word 𝑌 ∧ ((♯‘𝑤) − 1) ∈ (0...(♯‘𝑤))) → (♯‘(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩)) = ((♯‘𝑤) − 1))
108	99, 106, 107	syl2anc 573	. . . . . . . . . . . . . . . 16 ⊢ (((𝑚 ∈ ℕ₀ ∧ ∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)) ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → (♯‘(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩)) = ((♯‘𝑤) − 1))
109	88, 98, 108	3eqtr4d 2815	. . . . . . . . . . . . . . 15 ⊢ (((𝑚 ∈ ℕ₀ ∧ ∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)) ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → (♯‘(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩)) = (♯‘(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩)))
110	91	oveq1d 6806	. . . . . . . . . . . . . . . 16 ⊢ (((𝑚 ∈ ℕ₀ ∧ ∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)) ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → ((♯‘𝑥) − 1) = ((𝑚 + 1) − 1))
111		nn0cn 11502	. . . . . . . . . . . . . . . . . 18 ⊢ (𝑚 ∈ ℕ₀ → 𝑚 ∈ ℂ)
112	111	ad2antrr 705	. . . . . . . . . . . . . . . . 17 ⊢ (((𝑚 ∈ ℕ₀ ∧ ∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)) ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → 𝑚 ∈ ℂ)
113		ax-1cn 10194	. . . . . . . . . . . . . . . . 17 ⊢ 1 ∈ ℂ
114		pncan 10487	. . . . . . . . . . . . . . . . 17 ⊢ ((𝑚 ∈ ℂ ∧ 1 ∈ ℂ) → ((𝑚 + 1) − 1) = 𝑚)
115	112, 113, 114	sylancl 574	. . . . . . . . . . . . . . . 16 ⊢ (((𝑚 ∈ ℕ₀ ∧ ∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)) ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → ((𝑚 + 1) − 1) = 𝑚)
116	98, 110, 115	3eqtrd 2809	. . . . . . . . . . . . . . 15 ⊢ (((𝑚 ∈ ℕ₀ ∧ ∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)) ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → (♯‘(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩)) = 𝑚)
117	109, 116	jca 501	. . . . . . . . . . . . . 14 ⊢ (((𝑚 ∈ ℕ₀ ∧ ∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)) ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → ((♯‘(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩)) = (♯‘(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩)) ∧ (♯‘(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩)) = 𝑚))
118	70	adantr 466	. . . . . . . . . . . . . . . 16 ⊢ (((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ 𝑢 = (𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩)) → (𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) ∈ Word 𝑋)
119		fveq2 6330	. . . . . . . . . . . . . . . . . . . . . 22 ⊢ (𝑦 = (𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) → (♯‘𝑦) = (♯‘(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩)))
120		fveq2 6330	. . . . . . . . . . . . . . . . . . . . . 22 ⊢ (𝑢 = (𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) → (♯‘𝑢) = (♯‘(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩)))
121	119, 120	eqeqan12d 2787	. . . . . . . . . . . . . . . . . . . . 21 ⊢ ((𝑦 = (𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) ∧ 𝑢 = (𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩)) → ((♯‘𝑦) = (♯‘𝑢) ↔ (♯‘(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩)) = (♯‘(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩))))
122	121	expcom 398	. . . . . . . . . . . . . . . . . . . 20 ⊢ (𝑢 = (𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) → (𝑦 = (𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) → ((♯‘𝑦) = (♯‘𝑢) ↔ (♯‘(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩)) = (♯‘(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩)))))
123	122	adantl 467	. . . . . . . . . . . . . . . . . . 19 ⊢ (((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ 𝑢 = (𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩)) → (𝑦 = (𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) → ((♯‘𝑦) = (♯‘𝑢) ↔ (♯‘(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩)) = (♯‘(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩)))))
124	123	imp 393	. . . . . . . . . . . . . . . . . 18 ⊢ ((((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ 𝑢 = (𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩)) ∧ 𝑦 = (𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩)) → ((♯‘𝑦) = (♯‘𝑢) ↔ (♯‘(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩)) = (♯‘(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩))))
125	119	eqeq1d 2773	. . . . . . . . . . . . . . . . . . 19 ⊢ (𝑦 = (𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) → ((♯‘𝑦) = 𝑚 ↔ (♯‘(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩)) = 𝑚))
126	125	adantl 467	. . . . . . . . . . . . . . . . . 18 ⊢ ((((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ 𝑢 = (𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩)) ∧ 𝑦 = (𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩)) → ((♯‘𝑦) = 𝑚 ↔ (♯‘(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩)) = 𝑚))
127	124, 126	anbi12d 616	. . . . . . . . . . . . . . . . 17 ⊢ ((((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ 𝑢 = (𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩)) ∧ 𝑦 = (𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩)) → (((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) ↔ ((♯‘(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩)) = (♯‘(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩)) ∧ (♯‘(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩)) = 𝑚)))
128		vex 3354	. . . . . . . . . . . . . . . . . . . . 21 ⊢ 𝑦 ∈ V
129		vex 3354	. . . . . . . . . . . . . . . . . . . . 21 ⊢ 𝑢 ∈ V
130	128, 129, 44	sbc2ie 3655	. . . . . . . . . . . . . . . . . . . 20 ⊢ ([𝑦 / 𝑥][𝑢 / 𝑤]𝜑 ↔ 𝜒)
131	130	bicomi 214	. . . . . . . . . . . . . . . . . . 19 ⊢ (𝜒 ↔ [𝑦 / 𝑥][𝑢 / 𝑤]𝜑)
132	131	a1i 11	. . . . . . . . . . . . . . . . . 18 ⊢ ((((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ 𝑢 = (𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩)) ∧ 𝑦 = (𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩)) → (𝜒 ↔ [𝑦 / 𝑥][𝑢 / 𝑤]𝜑))
133		simpr 471	. . . . . . . . . . . . . . . . . . 19 ⊢ ((((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ 𝑢 = (𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩)) ∧ 𝑦 = (𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩)) → 𝑦 = (𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩))
134	133	sbceq1d 3592	. . . . . . . . . . . . . . . . . 18 ⊢ ((((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ 𝑢 = (𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩)) ∧ 𝑦 = (𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩)) → ([𝑦 / 𝑥][𝑢 / 𝑤]𝜑 ↔ [(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) / 𝑥][𝑢 / 𝑤]𝜑))
135		dfsbcq 3589	. . . . . . . . . . . . . . . . . . . . 21 ⊢ (𝑢 = (𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) → ([𝑢 / 𝑤]𝜑 ↔ [(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) / 𝑤]𝜑))
136	135	sbcbidv 3642	. . . . . . . . . . . . . . . . . . . 20 ⊢ (𝑢 = (𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) → ([(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) / 𝑥][𝑢 / 𝑤]𝜑 ↔ [(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) / 𝑥][(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) / 𝑤]𝜑))
137	136	adantl 467	. . . . . . . . . . . . . . . . . . 19 ⊢ (((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ 𝑢 = (𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩)) → ([(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) / 𝑥][𝑢 / 𝑤]𝜑 ↔ [(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) / 𝑥][(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) / 𝑤]𝜑))
138	137	adantr 466	. . . . . . . . . . . . . . . . . 18 ⊢ ((((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ 𝑢 = (𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩)) ∧ 𝑦 = (𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩)) → ([(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) / 𝑥][𝑢 / 𝑤]𝜑 ↔ [(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) / 𝑥][(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) / 𝑤]𝜑))
139	132, 134, 138	3bitrd 294	. . . . . . . . . . . . . . . . 17 ⊢ ((((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ 𝑢 = (𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩)) ∧ 𝑦 = (𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩)) → (𝜒 ↔ [(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) / 𝑥][(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) / 𝑤]𝜑))
140	127, 139	imbi12d 333	. . . . . . . . . . . . . . . 16 ⊢ ((((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ 𝑢 = (𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩)) ∧ 𝑦 = (𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩)) → ((((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒) ↔ (((♯‘(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩)) = (♯‘(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩)) ∧ (♯‘(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩)) = 𝑚) → [(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) / 𝑥][(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) / 𝑤]𝜑)))
141	118, 140	rspcdv 3463	. . . . . . . . . . . . . . 15 ⊢ (((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ 𝑢 = (𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩)) → (∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒) → (((♯‘(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩)) = (♯‘(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩)) ∧ (♯‘(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩)) = 𝑚) → [(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) / 𝑥][(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) / 𝑤]𝜑)))
142	50, 141	rspcimdv 3461	. . . . . . . . . . . . . 14 ⊢ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) → (∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒) → (((♯‘(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩)) = (♯‘(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩)) ∧ (♯‘(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩)) = 𝑚) → [(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) / 𝑥][(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) / 𝑤]𝜑)))
143	85, 86, 117, 142	syl3c 66	. . . . . . . . . . . . 13 ⊢ (((𝑚 ∈ ℕ₀ ∧ ∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)) ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → [(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) / 𝑥][(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) / 𝑤]𝜑)
144	143, 109	jca 501	. . . . . . . . . . . 12 ⊢ (((𝑚 ∈ ℕ₀ ∧ ∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)) ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → ([(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) / 𝑥][(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) / 𝑤]𝜑 ∧ (♯‘(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩)) = (♯‘(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩))))
145		dfsbcq 3589	. . . . . . . . . . . . . . . 16 ⊢ (𝑢 = (𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) → ([𝑢 / 𝑤][𝑦 / 𝑥]𝜑 ↔ [(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) / 𝑤][𝑦 / 𝑥]𝜑))
146		sbccom 3659	. . . . . . . . . . . . . . . 16 ⊢ ([(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) / 𝑤][𝑦 / 𝑥]𝜑 ↔ [𝑦 / 𝑥][(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) / 𝑤]𝜑)
147	145, 146	syl6bb 276	. . . . . . . . . . . . . . 15 ⊢ (𝑢 = (𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) → ([𝑢 / 𝑤][𝑦 / 𝑥]𝜑 ↔ [𝑦 / 𝑥][(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) / 𝑤]𝜑))
148	120	eqeq2d 2781	. . . . . . . . . . . . . . 15 ⊢ (𝑢 = (𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) → ((♯‘𝑦) = (♯‘𝑢) ↔ (♯‘𝑦) = (♯‘(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩))))
149	147, 148	anbi12d 616	. . . . . . . . . . . . . 14 ⊢ (𝑢 = (𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) → (([𝑢 / 𝑤][𝑦 / 𝑥]𝜑 ∧ (♯‘𝑦) = (♯‘𝑢)) ↔ ([𝑦 / 𝑥][(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) / 𝑤]𝜑 ∧ (♯‘𝑦) = (♯‘(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩)))))
150		oveq1 6798	. . . . . . . . . . . . . . 15 ⊢ (𝑢 = (𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) → (𝑢 ++ ⟨“𝑠”⟩) = ((𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ++ ⟨“𝑠”⟩))
151	150	sbceq1d 3592	. . . . . . . . . . . . . 14 ⊢ (𝑢 = (𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) → ([(𝑢 ++ ⟨“𝑠”⟩) / 𝑤][(𝑦 ++ ⟨“𝑧”⟩) / 𝑥]𝜑 ↔ [((𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ++ ⟨“𝑠”⟩) / 𝑤][(𝑦 ++ ⟨“𝑧”⟩) / 𝑥]𝜑))
152	149, 151	imbi12d 333	. . . . . . . . . . . . 13 ⊢ (𝑢 = (𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) → ((([𝑢 / 𝑤][𝑦 / 𝑥]𝜑 ∧ (♯‘𝑦) = (♯‘𝑢)) → [(𝑢 ++ ⟨“𝑠”⟩) / 𝑤][(𝑦 ++ ⟨“𝑧”⟩) / 𝑥]𝜑) ↔ (([𝑦 / 𝑥][(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) / 𝑤]𝜑 ∧ (♯‘𝑦) = (♯‘(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩))) → [((𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ++ ⟨“𝑠”⟩) / 𝑤][(𝑦 ++ ⟨“𝑧”⟩) / 𝑥]𝜑)))
153		s1eq 13573	. . . . . . . . . . . . . . . . 17 ⊢ (𝑠 = (lastS‘𝑤) → ⟨“𝑠”⟩ = ⟨“(lastS‘𝑤)”⟩)
154	153	oveq2d 6807	. . . . . . . . . . . . . . . 16 ⊢ (𝑠 = (lastS‘𝑤) → ((𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ++ ⟨“𝑠”⟩) = ((𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ++ ⟨“(lastS‘𝑤)”⟩))
155	154	sbceq1d 3592	. . . . . . . . . . . . . . 15 ⊢ (𝑠 = (lastS‘𝑤) → ([((𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ++ ⟨“𝑠”⟩) / 𝑤][(𝑦 ++ ⟨“𝑧”⟩) / 𝑥]𝜑 ↔ [((𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ++ ⟨“(lastS‘𝑤)”⟩) / 𝑤][(𝑦 ++ ⟨“𝑧”⟩) / 𝑥]𝜑))
156	155	imbi2d 329	. . . . . . . . . . . . . 14 ⊢ (𝑠 = (lastS‘𝑤) → ((([𝑦 / 𝑥][(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) / 𝑤]𝜑 ∧ (♯‘𝑦) = (♯‘(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩))) → [((𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ++ ⟨“𝑠”⟩) / 𝑤][(𝑦 ++ ⟨“𝑧”⟩) / 𝑥]𝜑) ↔ (([𝑦 / 𝑥][(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) / 𝑤]𝜑 ∧ (♯‘𝑦) = (♯‘(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩))) → [((𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ++ ⟨“(lastS‘𝑤)”⟩) / 𝑤][(𝑦 ++ ⟨“𝑧”⟩) / 𝑥]𝜑)))
157		sbccom 3659	. . . . . . . . . . . . . . . 16 ⊢ ([((𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ++ ⟨“(lastS‘𝑤)”⟩) / 𝑤][(𝑦 ++ ⟨“𝑧”⟩) / 𝑥]𝜑 ↔ [(𝑦 ++ ⟨“𝑧”⟩) / 𝑥][((𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ++ ⟨“(lastS‘𝑤)”⟩) / 𝑤]𝜑)
158	157	a1i 11	. . . . . . . . . . . . . . 15 ⊢ (𝑠 = (lastS‘𝑤) → ([((𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ++ ⟨“(lastS‘𝑤)”⟩) / 𝑤][(𝑦 ++ ⟨“𝑧”⟩) / 𝑥]𝜑 ↔ [(𝑦 ++ ⟨“𝑧”⟩) / 𝑥][((𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ++ ⟨“(lastS‘𝑤)”⟩) / 𝑤]𝜑))
159	158	imbi2d 329	. . . . . . . . . . . . . 14 ⊢ (𝑠 = (lastS‘𝑤) → ((([𝑦 / 𝑥][(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) / 𝑤]𝜑 ∧ (♯‘𝑦) = (♯‘(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩))) → [((𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ++ ⟨“(lastS‘𝑤)”⟩) / 𝑤][(𝑦 ++ ⟨“𝑧”⟩) / 𝑥]𝜑) ↔ (([𝑦 / 𝑥][(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) / 𝑤]𝜑 ∧ (♯‘𝑦) = (♯‘(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩))) → [(𝑦 ++ ⟨“𝑧”⟩) / 𝑥][((𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ++ ⟨“(lastS‘𝑤)”⟩) / 𝑤]𝜑)))
160	156, 159	bitrd 268	. . . . . . . . . . . . 13 ⊢ (𝑠 = (lastS‘𝑤) → ((([𝑦 / 𝑥][(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) / 𝑤]𝜑 ∧ (♯‘𝑦) = (♯‘(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩))) → [((𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ++ ⟨“𝑠”⟩) / 𝑤][(𝑦 ++ ⟨“𝑧”⟩) / 𝑥]𝜑) ↔ (([𝑦 / 𝑥][(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) / 𝑤]𝜑 ∧ (♯‘𝑦) = (♯‘(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩))) → [(𝑦 ++ ⟨“𝑧”⟩) / 𝑥][((𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ++ ⟨“(lastS‘𝑤)”⟩) / 𝑤]𝜑)))
161		dfsbcq 3589	. . . . . . . . . . . . . . 15 ⊢ (𝑦 = (𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) → ([𝑦 / 𝑥][(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) / 𝑤]𝜑 ↔ [(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) / 𝑥][(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) / 𝑤]𝜑))
162	119	eqeq1d 2773	. . . . . . . . . . . . . . 15 ⊢ (𝑦 = (𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) → ((♯‘𝑦) = (♯‘(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩)) ↔ (♯‘(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩)) = (♯‘(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩))))
163	161, 162	anbi12d 616	. . . . . . . . . . . . . 14 ⊢ (𝑦 = (𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) → (([𝑦 / 𝑥][(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) / 𝑤]𝜑 ∧ (♯‘𝑦) = (♯‘(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩))) ↔ ([(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) / 𝑥][(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) / 𝑤]𝜑 ∧ (♯‘(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩)) = (♯‘(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩)))))
164		oveq1 6798	. . . . . . . . . . . . . . 15 ⊢ (𝑦 = (𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) → (𝑦 ++ ⟨“𝑧”⟩) = ((𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) ++ ⟨“𝑧”⟩))
165	164	sbceq1d 3592	. . . . . . . . . . . . . 14 ⊢ (𝑦 = (𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) → ([(𝑦 ++ ⟨“𝑧”⟩) / 𝑥][((𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ++ ⟨“(lastS‘𝑤)”⟩) / 𝑤]𝜑 ↔ [((𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) ++ ⟨“𝑧”⟩) / 𝑥][((𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ++ ⟨“(lastS‘𝑤)”⟩) / 𝑤]𝜑))
166	163, 165	imbi12d 333	. . . . . . . . . . . . 13 ⊢ (𝑦 = (𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) → ((([𝑦 / 𝑥][(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) / 𝑤]𝜑 ∧ (♯‘𝑦) = (♯‘(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩))) → [(𝑦 ++ ⟨“𝑧”⟩) / 𝑥][((𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ++ ⟨“(lastS‘𝑤)”⟩) / 𝑤]𝜑) ↔ (([(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) / 𝑥][(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) / 𝑤]𝜑 ∧ (♯‘(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩)) = (♯‘(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩))) → [((𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) ++ ⟨“𝑧”⟩) / 𝑥][((𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ++ ⟨“(lastS‘𝑤)”⟩) / 𝑤]𝜑)))
167		s1eq 13573	. . . . . . . . . . . . . . . 16 ⊢ (𝑧 = (lastS‘𝑥) → ⟨“𝑧”⟩ = ⟨“(lastS‘𝑥)”⟩)
168	167	oveq2d 6807	. . . . . . . . . . . . . . 15 ⊢ (𝑧 = (lastS‘𝑥) → ((𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) ++ ⟨“𝑧”⟩) = ((𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) ++ ⟨“(lastS‘𝑥)”⟩))
169	168	sbceq1d 3592	. . . . . . . . . . . . . 14 ⊢ (𝑧 = (lastS‘𝑥) → ([((𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) ++ ⟨“𝑧”⟩) / 𝑥][((𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ++ ⟨“(lastS‘𝑤)”⟩) / 𝑤]𝜑 ↔ [((𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) ++ ⟨“(lastS‘𝑥)”⟩) / 𝑥][((𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ++ ⟨“(lastS‘𝑤)”⟩) / 𝑤]𝜑))
170	169	imbi2d 329	. . . . . . . . . . . . 13 ⊢ (𝑧 = (lastS‘𝑥) → ((([(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) / 𝑥][(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) / 𝑤]𝜑 ∧ (♯‘(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩)) = (♯‘(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩))) → [((𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) ++ ⟨“𝑧”⟩) / 𝑥][((𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ++ ⟨“(lastS‘𝑤)”⟩) / 𝑤]𝜑) ↔ (([(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) / 𝑥][(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) / 𝑤]𝜑 ∧ (♯‘(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩)) = (♯‘(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩))) → [((𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) ++ ⟨“(lastS‘𝑥)”⟩) / 𝑥][((𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ++ ⟨“(lastS‘𝑤)”⟩) / 𝑤]𝜑)))
171		simplr 752	. . . . . . . . . . . . . . . . . 18 ⊢ ((((𝑢 ∈ Word 𝑌 ∧ 𝑠 ∈ 𝑌) ∧ (𝑦 ∈ Word 𝑋 ∧ 𝑧 ∈ 𝑋)) ∧ (♯‘𝑦) = (♯‘𝑢)) → (𝑦 ∈ Word 𝑋 ∧ 𝑧 ∈ 𝑋))
172		simpll 750	. . . . . . . . . . . . . . . . . 18 ⊢ ((((𝑢 ∈ Word 𝑌 ∧ 𝑠 ∈ 𝑌) ∧ (𝑦 ∈ Word 𝑋 ∧ 𝑧 ∈ 𝑋)) ∧ (♯‘𝑦) = (♯‘𝑢)) → (𝑢 ∈ Word 𝑌 ∧ 𝑠 ∈ 𝑌))
173		simpr 471	. . . . . . . . . . . . . . . . . 18 ⊢ ((((𝑢 ∈ Word 𝑌 ∧ 𝑠 ∈ 𝑌) ∧ (𝑦 ∈ Word 𝑋 ∧ 𝑧 ∈ 𝑋)) ∧ (♯‘𝑦) = (♯‘𝑢)) → (♯‘𝑦) = (♯‘𝑢))
174		wrd2ind.7	. . . . . . . . . . . . . . . . . 18 ⊢ (((𝑦 ∈ Word 𝑋 ∧ 𝑧 ∈ 𝑋) ∧ (𝑢 ∈ Word 𝑌 ∧ 𝑠 ∈ 𝑌) ∧ (♯‘𝑦) = (♯‘𝑢)) → (𝜒 → 𝜃))
175	171, 172, 173, 174	syl3anc 1476	. . . . . . . . . . . . . . . . 17 ⊢ ((((𝑢 ∈ Word 𝑌 ∧ 𝑠 ∈ 𝑌) ∧ (𝑦 ∈ Word 𝑋 ∧ 𝑧 ∈ 𝑋)) ∧ (♯‘𝑦) = (♯‘𝑢)) → (𝜒 → 𝜃))
176	44	ancoms 446	. . . . . . . . . . . . . . . . . 18 ⊢ ((𝑤 = 𝑢 ∧ 𝑥 = 𝑦) → (𝜑 ↔ 𝜒))
177	129, 128, 176	sbc2ie 3655	. . . . . . . . . . . . . . . . 17 ⊢ ([𝑢 / 𝑤][𝑦 / 𝑥]𝜑 ↔ 𝜒)
178		ovex 6821	. . . . . . . . . . . . . . . . . 18 ⊢ (𝑢 ++ ⟨“𝑠”⟩) ∈ V
179		ovex 6821	. . . . . . . . . . . . . . . . . 18 ⊢ (𝑦 ++ ⟨“𝑧”⟩) ∈ V
180		wrd2ind.3	. . . . . . . . . . . . . . . . . . 19 ⊢ ((𝑥 = (𝑦 ++ ⟨“𝑧”⟩) ∧ 𝑤 = (𝑢 ++ ⟨“𝑠”⟩)) → (𝜑 ↔ 𝜃))
181	180	ancoms 446	. . . . . . . . . . . . . . . . . 18 ⊢ ((𝑤 = (𝑢 ++ ⟨“𝑠”⟩) ∧ 𝑥 = (𝑦 ++ ⟨“𝑧”⟩)) → (𝜑 ↔ 𝜃))
182	178, 179, 181	sbc2ie 3655	. . . . . . . . . . . . . . . . 17 ⊢ ([(𝑢 ++ ⟨“𝑠”⟩) / 𝑤][(𝑦 ++ ⟨“𝑧”⟩) / 𝑥]𝜑 ↔ 𝜃)
183	175, 177, 182	3imtr4g 285	. . . . . . . . . . . . . . . 16 ⊢ ((((𝑢 ∈ Word 𝑌 ∧ 𝑠 ∈ 𝑌) ∧ (𝑦 ∈ Word 𝑋 ∧ 𝑧 ∈ 𝑋)) ∧ (♯‘𝑦) = (♯‘𝑢)) → ([𝑢 / 𝑤][𝑦 / 𝑥]𝜑 → [(𝑢 ++ ⟨“𝑠”⟩) / 𝑤][(𝑦 ++ ⟨“𝑧”⟩) / 𝑥]𝜑))
184	183	ex 397	. . . . . . . . . . . . . . 15 ⊢ (((𝑢 ∈ Word 𝑌 ∧ 𝑠 ∈ 𝑌) ∧ (𝑦 ∈ Word 𝑋 ∧ 𝑧 ∈ 𝑋)) → ((♯‘𝑦) = (♯‘𝑢) → ([𝑢 / 𝑤][𝑦 / 𝑥]𝜑 → [(𝑢 ++ ⟨“𝑠”⟩) / 𝑤][(𝑦 ++ ⟨“𝑧”⟩) / 𝑥]𝜑)))
185	184	com23 86	. . . . . . . . . . . . . 14 ⊢ (((𝑢 ∈ Word 𝑌 ∧ 𝑠 ∈ 𝑌) ∧ (𝑦 ∈ Word 𝑋 ∧ 𝑧 ∈ 𝑋)) → ([𝑢 / 𝑤][𝑦 / 𝑥]𝜑 → ((♯‘𝑦) = (♯‘𝑢) → [(𝑢 ++ ⟨“𝑠”⟩) / 𝑤][(𝑦 ++ ⟨“𝑧”⟩) / 𝑥]𝜑)))
186	185	impd 396	. . . . . . . . . . . . 13 ⊢ (((𝑢 ∈ Word 𝑌 ∧ 𝑠 ∈ 𝑌) ∧ (𝑦 ∈ Word 𝑋 ∧ 𝑧 ∈ 𝑋)) → (([𝑢 / 𝑤][𝑦 / 𝑥]𝜑 ∧ (♯‘𝑦) = (♯‘𝑢)) → [(𝑢 ++ ⟨“𝑠”⟩) / 𝑤][(𝑦 ++ ⟨“𝑧”⟩) / 𝑥]𝜑))
187	152, 160, 166, 170, 186	vtocl4ga 3429	. . . . . . . . . . . 12 ⊢ ((((𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ∈ Word 𝑌 ∧ (lastS‘𝑤) ∈ 𝑌) ∧ ((𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) ∈ Word 𝑋 ∧ (lastS‘𝑥) ∈ 𝑋)) → (([(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) / 𝑥][(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) / 𝑤]𝜑 ∧ (♯‘(𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩)) = (♯‘(𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩))) → [((𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) ++ ⟨“(lastS‘𝑥)”⟩) / 𝑥][((𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ++ ⟨“(lastS‘𝑤)”⟩) / 𝑤]𝜑))
188	84, 144, 187	sylc 65	. . . . . . . . . . 11 ⊢ (((𝑚 ∈ ℕ₀ ∧ ∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)) ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → [((𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) ++ ⟨“(lastS‘𝑥)”⟩) / 𝑥][((𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ++ ⟨“(lastS‘𝑤)”⟩) / 𝑤]𝜑)
189		eqtr2 2791	. . . . . . . . . . . . . . . 16 ⊢ (((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)) → (♯‘𝑤) = (𝑚 + 1))
190	189	ad2antll 708	. . . . . . . . . . . . . . 15 ⊢ (((𝑚 ∈ ℕ₀ ∧ ∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)) ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → (♯‘𝑤) = (𝑚 + 1))
191	190, 92	eqeltrd 2850	. . . . . . . . . . . . . 14 ⊢ (((𝑚 ∈ ℕ₀ ∧ ∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)) ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → (♯‘𝑤) ∈ ℕ)
192		wrdfin 13512	. . . . . . . . . . . . . . . . 17 ⊢ (𝑤 ∈ Word 𝑌 → 𝑤 ∈ Fin)
193	192	adantr 466	. . . . . . . . . . . . . . . 16 ⊢ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) → 𝑤 ∈ Fin)
194	193	ad2antrl 707	. . . . . . . . . . . . . . 15 ⊢ (((𝑚 ∈ ℕ₀ ∧ ∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)) ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → 𝑤 ∈ Fin)
195		hashnncl 13352	. . . . . . . . . . . . . . 15 ⊢ (𝑤 ∈ Fin → ((♯‘𝑤) ∈ ℕ ↔ 𝑤 ≠ ∅))
196	194, 195	syl 17	. . . . . . . . . . . . . 14 ⊢ (((𝑚 ∈ ℕ₀ ∧ ∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)) ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → ((♯‘𝑤) ∈ ℕ ↔ 𝑤 ≠ ∅))
197	191, 196	mpbid 222	. . . . . . . . . . . . 13 ⊢ (((𝑚 ∈ ℕ₀ ∧ ∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)) ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → 𝑤 ≠ ∅)
198		swrdccatwrd 13670	. . . . . . . . . . . . . 14 ⊢ ((𝑤 ∈ Word 𝑌 ∧ 𝑤 ≠ ∅) → ((𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ++ ⟨“(lastS‘𝑤)”⟩) = 𝑤)
199	198	eqcomd 2777	. . . . . . . . . . . . 13 ⊢ ((𝑤 ∈ Word 𝑌 ∧ 𝑤 ≠ ∅) → 𝑤 = ((𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ++ ⟨“(lastS‘𝑤)”⟩))
200	99, 197, 199	syl2anc 573	. . . . . . . . . . . 12 ⊢ (((𝑚 ∈ ℕ₀ ∧ ∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)) ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → 𝑤 = ((𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ++ ⟨“(lastS‘𝑤)”⟩))
201		wrdfin 13512	. . . . . . . . . . . . . . . . 17 ⊢ (𝑥 ∈ Word 𝑋 → 𝑥 ∈ Fin)
202	201	adantl 467	. . . . . . . . . . . . . . . 16 ⊢ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) → 𝑥 ∈ Fin)
203	202	ad2antrl 707	. . . . . . . . . . . . . . 15 ⊢ (((𝑚 ∈ ℕ₀ ∧ ∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)) ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → 𝑥 ∈ Fin)
204		hashnncl 13352	. . . . . . . . . . . . . . 15 ⊢ (𝑥 ∈ Fin → ((♯‘𝑥) ∈ ℕ ↔ 𝑥 ≠ ∅))
205	203, 204	syl 17	. . . . . . . . . . . . . 14 ⊢ (((𝑚 ∈ ℕ₀ ∧ ∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)) ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → ((♯‘𝑥) ∈ ℕ ↔ 𝑥 ≠ ∅))
206	93, 205	mpbid 222	. . . . . . . . . . . . 13 ⊢ (((𝑚 ∈ ℕ₀ ∧ ∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)) ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → 𝑥 ≠ ∅)
207		swrdccatwrd 13670	. . . . . . . . . . . . . 14 ⊢ ((𝑥 ∈ Word 𝑋 ∧ 𝑥 ≠ ∅) → ((𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) ++ ⟨“(lastS‘𝑥)”⟩) = 𝑥)
208	207	eqcomd 2777	. . . . . . . . . . . . 13 ⊢ ((𝑥 ∈ Word 𝑋 ∧ 𝑥 ≠ ∅) → 𝑥 = ((𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) ++ ⟨“(lastS‘𝑥)”⟩))
209	89, 206, 208	syl2anc 573	. . . . . . . . . . . 12 ⊢ (((𝑚 ∈ ℕ₀ ∧ ∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)) ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → 𝑥 = ((𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) ++ ⟨“(lastS‘𝑥)”⟩))
210		sbceq1a 3598	. . . . . . . . . . . . 13 ⊢ (𝑤 = ((𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ++ ⟨“(lastS‘𝑤)”⟩) → (𝜑 ↔ [((𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ++ ⟨“(lastS‘𝑤)”⟩) / 𝑤]𝜑))
211		sbceq1a 3598	. . . . . . . . . . . . 13 ⊢ (𝑥 = ((𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) ++ ⟨“(lastS‘𝑥)”⟩) → ([((𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ++ ⟨“(lastS‘𝑤)”⟩) / 𝑤]𝜑 ↔ [((𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) ++ ⟨“(lastS‘𝑥)”⟩) / 𝑥][((𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ++ ⟨“(lastS‘𝑤)”⟩) / 𝑤]𝜑))
212	210, 211	sylan9bb 499	. . . . . . . . . . . 12 ⊢ ((𝑤 = ((𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ++ ⟨“(lastS‘𝑤)”⟩) ∧ 𝑥 = ((𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) ++ ⟨“(lastS‘𝑥)”⟩)) → (𝜑 ↔ [((𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) ++ ⟨“(lastS‘𝑥)”⟩) / 𝑥][((𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ++ ⟨“(lastS‘𝑤)”⟩) / 𝑤]𝜑))
213	200, 209, 212	syl2anc 573	. . . . . . . . . . 11 ⊢ (((𝑚 ∈ ℕ₀ ∧ ∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)) ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → (𝜑 ↔ [((𝑥 substr ⟨0, ((♯‘𝑥) − 1)⟩) ++ ⟨“(lastS‘𝑥)”⟩) / 𝑥][((𝑤 substr ⟨0, ((♯‘𝑤) − 1)⟩) ++ ⟨“(lastS‘𝑤)”⟩) / 𝑤]𝜑))
214	188, 213	mpbird 247	. . . . . . . . . 10 ⊢ (((𝑚 ∈ ℕ₀ ∧ ∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)) ∧ ((𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋) ∧ ((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)))) → 𝜑)
215	214	expr 444	. . . . . . . . 9 ⊢ (((𝑚 ∈ ℕ₀ ∧ ∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)) ∧ (𝑤 ∈ Word 𝑌 ∧ 𝑥 ∈ Word 𝑋)) → (((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)) → 𝜑))
216	215	ralrimivva 3120	. . . . . . . 8 ⊢ ((𝑚 ∈ ℕ₀ ∧ ∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒)) → ∀𝑤 ∈ Word 𝑌∀𝑥 ∈ Word 𝑋(((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)) → 𝜑))
217	216	ex 397	. . . . . . 7 ⊢ (𝑚 ∈ ℕ₀ → (∀𝑢 ∈ Word 𝑌∀𝑦 ∈ Word 𝑋(((♯‘𝑦) = (♯‘𝑢) ∧ (♯‘𝑦) = 𝑚) → 𝜒) → ∀𝑤 ∈ Word 𝑌∀𝑥 ∈ Word 𝑋(((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)) → 𝜑)))
218	48, 217	syl5bi 232	. . . . . 6 ⊢ (𝑚 ∈ ℕ₀ → (∀𝑤 ∈ Word 𝑌∀𝑥 ∈ Word 𝑋(((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = 𝑚) → 𝜑) → ∀𝑤 ∈ Word 𝑌∀𝑥 ∈ Word 𝑋(((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (𝑚 + 1)) → 𝜑)))
219	5, 9, 13, 17, 37, 218	nn0ind 11672	. . . . 5 ⊢ ((♯‘𝐴) ∈ ℕ₀ → ∀𝑤 ∈ Word 𝑌∀𝑥 ∈ Word 𝑋(((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (♯‘𝐴)) → 𝜑))
220	1, 219	syl 17	. . . 4 ⊢ (𝐴 ∈ Word 𝑋 → ∀𝑤 ∈ Word 𝑌∀𝑥 ∈ Word 𝑋(((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (♯‘𝐴)) → 𝜑))
221	220	3ad2ant1 1127	. . 3 ⊢ ((𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ Word 𝑌 ∧ (♯‘𝐴) = (♯‘𝐵)) → ∀𝑤 ∈ Word 𝑌∀𝑥 ∈ Word 𝑋(((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (♯‘𝐴)) → 𝜑))
222		fveq2 6330	. . . . . . . . 9 ⊢ (𝑤 = 𝐵 → (♯‘𝑤) = (♯‘𝐵))
223	222	eqeq2d 2781	. . . . . . . 8 ⊢ (𝑤 = 𝐵 → ((♯‘𝑥) = (♯‘𝑤) ↔ (♯‘𝑥) = (♯‘𝐵)))
224	223	anbi1d 615	. . . . . . 7 ⊢ (𝑤 = 𝐵 → (((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (♯‘𝐴)) ↔ ((♯‘𝑥) = (♯‘𝐵) ∧ (♯‘𝑥) = (♯‘𝐴))))
225		wrd2ind.5	. . . . . . 7 ⊢ (𝑤 = 𝐵 → (𝜑 ↔ 𝜌))
226	224, 225	imbi12d 333	. . . . . 6 ⊢ (𝑤 = 𝐵 → ((((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (♯‘𝐴)) → 𝜑) ↔ (((♯‘𝑥) = (♯‘𝐵) ∧ (♯‘𝑥) = (♯‘𝐴)) → 𝜌)))
227	226	ralbidv 3135	. . . . 5 ⊢ (𝑤 = 𝐵 → (∀𝑥 ∈ Word 𝑋(((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (♯‘𝐴)) → 𝜑) ↔ ∀𝑥 ∈ Word 𝑋(((♯‘𝑥) = (♯‘𝐵) ∧ (♯‘𝑥) = (♯‘𝐴)) → 𝜌)))
228	227	rspcv 3456	. . . 4 ⊢ (𝐵 ∈ Word 𝑌 → (∀𝑤 ∈ Word 𝑌∀𝑥 ∈ Word 𝑋(((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (♯‘𝐴)) → 𝜑) → ∀𝑥 ∈ Word 𝑋(((♯‘𝑥) = (♯‘𝐵) ∧ (♯‘𝑥) = (♯‘𝐴)) → 𝜌)))
229	228	3ad2ant2 1128	. . 3 ⊢ ((𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ Word 𝑌 ∧ (♯‘𝐴) = (♯‘𝐵)) → (∀𝑤 ∈ Word 𝑌∀𝑥 ∈ Word 𝑋(((♯‘𝑥) = (♯‘𝑤) ∧ (♯‘𝑥) = (♯‘𝐴)) → 𝜑) → ∀𝑥 ∈ Word 𝑋(((♯‘𝑥) = (♯‘𝐵) ∧ (♯‘𝑥) = (♯‘𝐴)) → 𝜌)))
230	221, 229	mpd 15	. 2 ⊢ ((𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ Word 𝑌 ∧ (♯‘𝐴) = (♯‘𝐵)) → ∀𝑥 ∈ Word 𝑋(((♯‘𝑥) = (♯‘𝐵) ∧ (♯‘𝑥) = (♯‘𝐴)) → 𝜌))
231		eqidd 2772	. 2 ⊢ ((𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ Word 𝑌 ∧ (♯‘𝐴) = (♯‘𝐵)) → (♯‘𝐴) = (♯‘𝐴))
232		fveq2 6330	. . . . . . . . . . 11 ⊢ (𝑥 = 𝐴 → (♯‘𝑥) = (♯‘𝐴))
233	232	eqeq1d 2773	. . . . . . . . . 10 ⊢ (𝑥 = 𝐴 → ((♯‘𝑥) = (♯‘𝐵) ↔ (♯‘𝐴) = (♯‘𝐵)))
234	232	eqeq1d 2773	. . . . . . . . . 10 ⊢ (𝑥 = 𝐴 → ((♯‘𝑥) = (♯‘𝐴) ↔ (♯‘𝐴) = (♯‘𝐴)))
235	233, 234	anbi12d 616	. . . . . . . . 9 ⊢ (𝑥 = 𝐴 → (((♯‘𝑥) = (♯‘𝐵) ∧ (♯‘𝑥) = (♯‘𝐴)) ↔ ((♯‘𝐴) = (♯‘𝐵) ∧ (♯‘𝐴) = (♯‘𝐴))))
236		wrd2ind.4	. . . . . . . . 9 ⊢ (𝑥 = 𝐴 → (𝜌 ↔ 𝜏))
237	235, 236	imbi12d 333	. . . . . . . 8 ⊢ (𝑥 = 𝐴 → ((((♯‘𝑥) = (♯‘𝐵) ∧ (♯‘𝑥) = (♯‘𝐴)) → 𝜌) ↔ (((♯‘𝐴) = (♯‘𝐵) ∧ (♯‘𝐴) = (♯‘𝐴)) → 𝜏)))
238	237	rspcv 3456	. . . . . . 7 ⊢ (𝐴 ∈ Word 𝑋 → (∀𝑥 ∈ Word 𝑋(((♯‘𝑥) = (♯‘𝐵) ∧ (♯‘𝑥) = (♯‘𝐴)) → 𝜌) → (((♯‘𝐴) = (♯‘𝐵) ∧ (♯‘𝐴) = (♯‘𝐴)) → 𝜏)))
239	238	com23 86	. . . . . 6 ⊢ (𝐴 ∈ Word 𝑋 → (((♯‘𝐴) = (♯‘𝐵) ∧ (♯‘𝐴) = (♯‘𝐴)) → (∀𝑥 ∈ Word 𝑋(((♯‘𝑥) = (♯‘𝐵) ∧ (♯‘𝑥) = (♯‘𝐴)) → 𝜌) → 𝜏)))
240	239	expd 400	. . . . 5 ⊢ (𝐴 ∈ Word 𝑋 → ((♯‘𝐴) = (♯‘𝐵) → ((♯‘𝐴) = (♯‘𝐴) → (∀𝑥 ∈ Word 𝑋(((♯‘𝑥) = (♯‘𝐵) ∧ (♯‘𝑥) = (♯‘𝐴)) → 𝜌) → 𝜏))))
241	240	com34 91	. . . 4 ⊢ (𝐴 ∈ Word 𝑋 → ((♯‘𝐴) = (♯‘𝐵) → (∀𝑥 ∈ Word 𝑋(((♯‘𝑥) = (♯‘𝐵) ∧ (♯‘𝑥) = (♯‘𝐴)) → 𝜌) → ((♯‘𝐴) = (♯‘𝐴) → 𝜏))))
242	241	imp 393	. . 3 ⊢ ((𝐴 ∈ Word 𝑋 ∧ (♯‘𝐴) = (♯‘𝐵)) → (∀𝑥 ∈ Word 𝑋(((♯‘𝑥) = (♯‘𝐵) ∧ (♯‘𝑥) = (♯‘𝐴)) → 𝜌) → ((♯‘𝐴) = (♯‘𝐴) → 𝜏)))
243	242	3adant2 1125	. 2 ⊢ ((𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ Word 𝑌 ∧ (♯‘𝐴) = (♯‘𝐵)) → (∀𝑥 ∈ Word 𝑋(((♯‘𝑥) = (♯‘𝐵) ∧ (♯‘𝑥) = (♯‘𝐴)) → 𝜌) → ((♯‘𝐴) = (♯‘𝐴) → 𝜏)))
244	230, 231, 243	mp2d 49	1 ⊢ ((𝐴 ∈ Word 𝑋 ∧ 𝐵 ∈ Word 𝑌 ∧ (♯‘𝐴) = (♯‘𝐵)) → 𝜏)

Colors of variables: wff setvar class

Syntax hints: → wi 4 ↔ wb 196 ∧ wa 382 ∧ w3a 1071 = wceq 1631 ∈ wcel 2145 ≠ wne 2943 ∀wral 3061 [wsbc 3587 ∅c0 4063 ⟨cop 4322 class class class wbr 4786 ‘cfv 6029 (class class class)co 6791 Fincfn 8107 ℂcc 10134 0cc0 10136 1c1 10137 + caddc 10139 ≤ cle 10275 − cmin 10466 ℕcn 11220 ℕ₀cn0 11492 ...cfz 12526 ..^cfzo 12666 ♯chash 13314 Word cword 13480 lastSclsw 13481 ++ cconcat 13482 ⟨“cs1 13483 substr csubstr 13484

This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1870 ax-4 1885 ax-5 1991 ax-6 2057 ax-7 2093 ax-8 2147 ax-9 2154 ax-10 2174 ax-11 2190 ax-12 2203 ax-13 2408 ax-ext 2751 ax-rep 4904 ax-sep 4915 ax-nul 4923 ax-pow 4974 ax-pr 5034 ax-un 7094 ax-cnex 10192 ax-resscn 10193 ax-1cn 10194 ax-icn 10195 ax-addcl 10196 ax-addrcl 10197 ax-mulcl 10198 ax-mulrcl 10199 ax-mulcom 10200 ax-addass 10201 ax-mulass 10202 ax-distr 10203 ax-i2m1 10204 ax-1ne0 10205 ax-1rid 10206 ax-rnegex 10207 ax-rrecex 10208 ax-cnre 10209 ax-pre-lttri 10210 ax-pre-lttrn 10211 ax-pre-ltadd 10212 ax-pre-mulgt0 10213

This theorem depends on definitions: df-bi 197 df-an 383 df-or 837 df-3or 1072 df-3an 1073 df-tru 1634 df-ex 1853 df-nf 1858 df-sb 2050 df-eu 2622 df-mo 2623 df-clab 2758 df-cleq 2764 df-clel 2767 df-nfc 2902 df-ne 2944 df-nel 3047 df-ral 3066 df-rex 3067 df-reu 3068 df-rab 3070 df-v 3353 df-sbc 3588 df-csb 3683 df-dif 3726 df-un 3728 df-in 3730 df-ss 3737 df-pss 3739 df-nul 4064 df-if 4226 df-pw 4299 df-sn 4317 df-pr 4319 df-tp 4321 df-op 4323 df-uni 4575 df-int 4612 df-iun 4656 df-br 4787 df-opab 4847 df-mpt 4864 df-tr 4887 df-id 5157 df-eprel 5162 df-po 5170 df-so 5171 df-fr 5208 df-we 5210 df-xp 5255 df-rel 5256 df-cnv 5257 df-co 5258 df-dm 5259 df-rn 5260 df-res 5261 df-ima 5262 df-pred 5821 df-ord 5867 df-on 5868 df-lim 5869 df-suc 5870 df-iota 5992 df-fun 6031 df-fn 6032 df-f 6033 df-f1 6034 df-fo 6035 df-f1o 6036 df-fv 6037 df-riota 6752 df-ov 6794 df-oprab 6795 df-mpt2 6796 df-om 7211 df-1st 7313 df-2nd 7314 df-wrecs 7557 df-recs 7619 df-rdg 7657 df-1o 7711 df-oadd 7715 df-er 7894 df-en 8108 df-dom 8109 df-sdom 8110 df-fin 8111 df-card 8963 df-pnf 10276 df-mnf 10277 df-xr 10278 df-ltxr 10279 df-le 10280 df-sub 10468 df-neg 10469 df-nn 11221 df-n0 11493 df-xnn0 11564 df-z 11578 df-uz 11887 df-fz 12527 df-fzo 12667 df-hash 13315 df-word 13488 df-lsw 13489 df-concat 13490 df-s1 13491 df-substr 13492

This theorem is referenced by: gsmsymgreq 18052

W3C validator