Theorem wrd2ind 11308

Description: Perform induction over the structure of two words of the same length. (Contributed by AV, 23-Jan-2019.) (Proof shortened by AV, 12-Oct-2022.)

Hypotheses

Ref	Expression
wrd2ind.1	|- ( ( x = (/) /\ w = (/) ) -> ( ph <-> ps ) )
wrd2ind.2	|- ( ( x = y /\ w = u ) -> ( ph <-> ch ) )
wrd2ind.3	|- ( ( x = ( y ++ <" z "> ) /\ w = ( u ++ <" s "> ) ) -> ( ph <-> th ) )
wrd2ind.4	|- ( x = A -> ( rh <-> ta ) )
wrd2ind.5	|- ( w = B -> ( ph <-> rh ) )
wrd2ind.6	|- ps
wrd2ind.7	|- ( ( ( y e. Word X /\ z e. X ) /\ ( u e. Word Y /\ s e. Y ) /\ (♯ ` y ) = (♯ ` u ) ) -> ( ch -> th ) )

Assertion

Ref	Expression
wrd2ind	|- ( ( A e. Word X /\ B e. Word Y /\ (♯ ` A ) = (♯ ` B ) ) -> ta )

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   ch, w, x   ph, s, u, y, z   ta, x   th, w, x   rh, w

Allowed substitution hints:   ph( x, w)   ps( x, y, z, w, u, s)   ch( y, z, u, s)   th( y, z, u, s)   ta( y, z, w, u, s)   rh( 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 11121	. . . . 5 |- ( A e. Word X -> (♯ ` A ) e. NN0 )
2		eqeq2 2241	. . . . . . . . 9 |- ( n = 0 -> ( (♯ ` x ) = n <-> (♯ ` x ) = 0 ) )
3	2	anbi2d 464	. . . . . . . 8 |- ( n = 0 -> ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = n ) <-> ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = 0 ) ) )
4	3	imbi1d 231	. . . . . . 7 |- ( n = 0 -> ( ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = n ) -> ph ) <-> ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = 0 ) -> ph ) ) )
5	4	2ralbidv 2556	. . . . . 6 |- ( n = 0 -> ( A. w e. Word Y A. x e. Word X ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = n ) -> ph ) <-> A. w e. Word Y A. x e. Word X ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = 0 ) -> ph ) ) )
6		eqeq2 2241	. . . . . . . . 9 |- ( n = m -> ( (♯ ` x ) = n <-> (♯ ` x ) = m ) )
7	6	anbi2d 464	. . . . . . . 8 |- ( n = m -> ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = n ) <-> ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = m ) ) )
8	7	imbi1d 231	. . . . . . 7 |- ( n = m -> ( ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = n ) -> ph ) <-> ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = m ) -> ph ) ) )
9	8	2ralbidv 2556	. . . . . 6 |- ( n = m -> ( A. w e. Word Y A. x e. Word X ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = n ) -> ph ) <-> A. w e. Word Y A. x e. Word X ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = m ) -> ph ) ) )
10		eqeq2 2241	. . . . . . . . 9 |- ( n = ( m + 1 ) -> ( (♯ ` x ) = n <-> (♯ ` x ) = ( m + 1 ) ) )
11	10	anbi2d 464	. . . . . . . 8 |- ( n = ( m + 1 ) -> ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = n ) <-> ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) )
12	11	imbi1d 231	. . . . . . 7 |- ( n = ( m + 1 ) -> ( ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = n ) -> ph ) <-> ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) -> ph ) ) )
13	12	2ralbidv 2556	. . . . . 6 |- ( n = ( m + 1 ) -> ( A. w e. Word Y A. x e. Word X ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = n ) -> ph ) <-> A. w e. Word Y A. x e. Word X ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) -> ph ) ) )
14		eqeq2 2241	. . . . . . . . 9 |- ( n = (♯ ` A ) -> ( (♯ ` x ) = n <-> (♯ ` x ) = (♯ ` A ) ) )
15	14	anbi2d 464	. . . . . . . 8 |- ( n = (♯ ` A ) -> ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = n ) <-> ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = (♯ ` A ) ) ) )
16	15	imbi1d 231	. . . . . . 7 |- ( n = (♯ ` A ) -> ( ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = n ) -> ph ) <-> ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = (♯ ` A ) ) -> ph ) ) )
17	16	2ralbidv 2556	. . . . . 6 |- ( n = (♯ ` A ) -> ( A. w e. Word Y A. x e. Word X ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = n ) -> ph ) <-> A. w e. Word Y A. x e. Word X ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = (♯ ` A ) ) -> ph ) ) )
18		eqeq1 2238	. . . . . . . . . . 11 |- ( (♯ ` x ) = 0 -> ( (♯ ` x ) = (♯ ` w ) <-> 0 = (♯ ` w ) ) )
19	18	adantl 277	. . . . . . . . . 10 |- ( ( ( w e. Word Y /\ x e. Word X ) /\ (♯ ` x ) = 0 ) -> ( (♯ ` x ) = (♯ ` w ) <-> 0 = (♯ ` w ) ) )
20		eqcom 2233	. . . . . . . . . . . . . 14 |- ( 0 = (♯ ` w ) <-> (♯ ` w ) = 0 )
21		wrdfin 11136	. . . . . . . . . . . . . . 15 |- ( w e. Word Y -> w e. Fin )
22		fihasheq0 11056	. . . . . . . . . . . . . . 15 |- ( w e. Fin -> ( (♯ ` w ) = 0 <-> w = (/) ) )
23	21, 22	syl 14	. . . . . . . . . . . . . 14 |- ( w e. Word Y -> ( (♯ ` w ) = 0 <-> w = (/) ) )
24	20, 23	bitrid 192	. . . . . . . . . . . . 13 |- ( w e. Word Y -> ( 0 = (♯ ` w ) <-> w = (/) ) )
25		wrdfin 11136	. . . . . . . . . . . . . . . 16 |- ( x e. Word X -> x e. Fin )
26		fihasheq0 11056	. . . . . . . . . . . . . . . 16 |- ( x e. Fin -> ( (♯ ` x ) = 0 <-> x = (/) ) )
27	25, 26	syl 14	. . . . . . . . . . . . . . 15 |- ( x e. Word X -> ( (♯ ` x ) = 0 <-> x = (/) ) )
28		wrd2ind.6	. . . . . . . . . . . . . . . . 17 |- ps
29		wrd2ind.1	. . . . . . . . . . . . . . . . 17 |- ( ( x = (/) /\ w = (/) ) -> ( ph <-> ps ) )
30	28, 29	mpbiri 168	. . . . . . . . . . . . . . . 16 |- ( ( x = (/) /\ w = (/) ) -> ph )
31	30	ex 115	. . . . . . . . . . . . . . 15 |- ( x = (/) -> ( w = (/) -> ph ) )
32	27, 31	biimtrdi 163	. . . . . . . . . . . . . 14 |- ( x e. Word X -> ( (♯ ` x ) = 0 -> ( w = (/) -> ph ) ) )
33	32	com13 80	. . . . . . . . . . . . 13 |- ( w = (/) -> ( (♯ ` x ) = 0 -> ( x e. Word X -> ph ) ) )
34	24, 33	biimtrdi 163	. . . . . . . . . . . 12 |- ( w e. Word Y -> ( 0 = (♯ ` w ) -> ( (♯ ` x ) = 0 -> ( x e. Word X -> ph ) ) ) )
35	34	com24 87	. . . . . . . . . . 11 |- ( w e. Word Y -> ( x e. Word X -> ( (♯ ` x ) = 0 -> ( 0 = (♯ ` w ) -> ph ) ) ) )
36	35	imp31 256	. . . . . . . . . 10 |- ( ( ( w e. Word Y /\ x e. Word X ) /\ (♯ ` x ) = 0 ) -> ( 0 = (♯ ` w ) -> ph ) )
37	19, 36	sylbid 150	. . . . . . . . 9 |- ( ( ( w e. Word Y /\ x e. Word X ) /\ (♯ ` x ) = 0 ) -> ( (♯ ` x ) = (♯ ` w ) -> ph ) )
38	37	ex 115	. . . . . . . 8 |- ( ( w e. Word Y /\ x e. Word X ) -> ( (♯ ` x ) = 0 -> ( (♯ ` x ) = (♯ ` w ) -> ph ) ) )
39	38	impcomd 255	. . . . . . 7 |- ( ( w e. Word Y /\ x e. Word X ) -> ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = 0 ) -> ph ) )
40	39	rgen2 2618	. . . . . 6 |- A. w e. Word Y A. x e. Word X ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = 0 ) -> ph )
41		fveq2 5639	. . . . . . . . . . . . 13 |- ( x = y -> (♯ ` x ) = (♯ ` y ) )
42		fveq2 5639	. . . . . . . . . . . . 13 |- ( w = u -> (♯ ` w ) = (♯ ` u ) )
43	41, 42	eqeqan12d 2247	. . . . . . . . . . . 12 |- ( ( x = y /\ w = u ) -> ( (♯ ` x ) = (♯ ` w ) <-> (♯ ` y ) = (♯ ` u ) ) )
44		fveqeq2 5648	. . . . . . . . . . . . 13 |- ( x = y -> ( (♯ ` x ) = m <-> (♯ ` y ) = m ) )
45	44	adantr 276	. . . . . . . . . . . 12 |- ( ( x = y /\ w = u ) -> ( (♯ ` x ) = m <-> (♯ ` y ) = m ) )
46	43, 45	anbi12d 473	. . . . . . . . . . 11 |- ( ( x = y /\ w = u ) -> ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = m ) <-> ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) ) )
47		wrd2ind.2	. . . . . . . . . . 11 |- ( ( x = y /\ w = u ) -> ( ph <-> ch ) )
48	46, 47	imbi12d 234	. . . . . . . . . 10 |- ( ( x = y /\ w = u ) -> ( ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = m ) -> ph ) <-> ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) )
49	48	ancoms 268	. . . . . . . . 9 |- ( ( w = u /\ x = y ) -> ( ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = m ) -> ph ) <-> ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) )
50	49	cbvraldva 2776	. . . . . . . 8 |- ( w = u -> ( A. x e. Word X ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = m ) -> ph ) <-> A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) )
51	50	cbvralvw 2771	. . . . . . 7 |- ( A. w e. Word Y A. x e. Word X ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = m ) -> ph ) <-> A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) )
52		lencl 11121	. . . . . . . . . . . . . . . . . . . 20 |- ( w e. Word Y -> (♯ ` w ) e. NN0 )
53	52	nn0zd 9600	. . . . . . . . . . . . . . . . . . 19 |- ( w e. Word Y -> (♯ ` w ) e. ZZ )
54		1zzd 9506	. . . . . . . . . . . . . . . . . . 19 |- ( w e. Word Y -> 1 e. ZZ )
55	53, 54	zsubcld 9607	. . . . . . . . . . . . . . . . . 18 |- ( w e. Word Y -> ( (♯ ` w ) - 1 ) e. ZZ )
56		pfxclz 11264	. . . . . . . . . . . . . . . . . 18 |- ( ( w e. Word Y /\ ( (♯ ` w ) - 1 ) e. ZZ ) -> ( w prefix ( (♯ ` w ) - 1 ) ) e. Word Y )
57	55, 56	mpdan 421	. . . . . . . . . . . . . . . . 17 |- ( w e. Word Y -> ( w prefix ( (♯ ` w ) - 1 ) ) e. Word Y )
58	57	adantr 276	. . . . . . . . . . . . . . . 16 |- ( ( w e. Word Y /\ x e. Word X ) -> ( w prefix ( (♯ ` w ) - 1 ) ) e. Word Y )
59	58	ad2antrl 490	. . . . . . . . . . . . . . 15 |- ( ( m e. NN0 /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> ( w prefix ( (♯ ` w ) - 1 ) ) e. Word Y )
60		simprll 539	. . . . . . . . . . . . . . . 16 |- ( ( m e. NN0 /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> w e. Word Y )
61		eqeq1 2238	. . . . . . . . . . . . . . . . . . . . . 22 |- ( (♯ ` x ) = ( m + 1 ) -> ( (♯ ` x ) = (♯ ` w ) <-> ( m + 1 ) = (♯ ` w ) ) )
62		nn0p1nn 9441	. . . . . . . . . . . . . . . . . . . . . . 23 |- ( m e. NN0 -> ( m + 1 ) e. NN )
63		eleq1 2294	. . . . . . . . . . . . . . . . . . . . . . . 24 |- ( (♯ ` w ) = ( m + 1 ) -> ( (♯ ` w ) e. NN <-> ( m + 1 ) e. NN ) )
64	63	eqcoms 2234	. . . . . . . . . . . . . . . . . . . . . . 23 |- ( ( m + 1 ) = (♯ ` w ) -> ( (♯ ` w ) e. NN <-> ( m + 1 ) e. NN ) )
65	62, 64	imbitrrid 156	. . . . . . . . . . . . . . . . . . . . . 22 |- ( ( m + 1 ) = (♯ ` w ) -> ( m e. NN0 -> (♯ ` w ) e. NN ) )
66	61, 65	biimtrdi 163	. . . . . . . . . . . . . . . . . . . . 21 |- ( (♯ ` x ) = ( m + 1 ) -> ( (♯ ` x ) = (♯ ` w ) -> ( m e. NN0 -> (♯ ` w ) e. NN ) ) )
67	66	impcom 125	. . . . . . . . . . . . . . . . . . . 20 |- ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) -> ( m e. NN0 -> (♯ ` w ) e. NN ) )
68	67	adantl 277	. . . . . . . . . . . . . . . . . . 19 |- ( ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) -> ( m e. NN0 -> (♯ ` w ) e. NN ) )
69	68	impcom 125	. . . . . . . . . . . . . . . . . 18 |- ( ( m e. NN0 /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> (♯ ` w ) e. NN )
70	69	nnge1d 9186	. . . . . . . . . . . . . . . . 17 |- ( ( m e. NN0 /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> 1 <_ (♯ ` w ) )
71		wrdlenge1n0 11151	. . . . . . . . . . . . . . . . . 18 |- ( w e. Word Y -> ( w =/= (/) <-> 1 <_ (♯ ` w ) ) )
72	60, 71	syl 14	. . . . . . . . . . . . . . . . 17 |- ( ( m e. NN0 /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> ( w =/= (/) <-> 1 <_ (♯ ` w ) ) )
73	70, 72	mpbird 167	. . . . . . . . . . . . . . . 16 |- ( ( m e. NN0 /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> w =/= (/) )
74		lswcl 11168	. . . . . . . . . . . . . . . 16 |- ( ( w e. Word Y /\ w =/= (/) ) -> (lastS ` w ) e. Y )
75	60, 73, 74	syl2anc 411	. . . . . . . . . . . . . . 15 |- ( ( m e. NN0 /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> (lastS ` w ) e. Y )
76	59, 75	jca 306	. . . . . . . . . . . . . 14 |- ( ( m e. NN0 /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> ( ( w prefix ( (♯ ` w ) - 1 ) ) e. Word Y /\ (lastS ` w ) e. Y ) )
77		lencl 11121	. . . . . . . . . . . . . . . . . . 19 |- ( x e. Word X -> (♯ ` x ) e. NN0 )
78	77	nn0zd 9600	. . . . . . . . . . . . . . . . . 18 |- ( x e. Word X -> (♯ ` x ) e. ZZ )
79		1zzd 9506	. . . . . . . . . . . . . . . . . 18 |- ( x e. Word X -> 1 e. ZZ )
80	78, 79	zsubcld 9607	. . . . . . . . . . . . . . . . 17 |- ( x e. Word X -> ( (♯ ` x ) - 1 ) e. ZZ )
81		pfxclz 11264	. . . . . . . . . . . . . . . . 17 |- ( ( x e. Word X /\ ( (♯ ` x ) - 1 ) e. ZZ ) -> ( x prefix ( (♯ ` x ) - 1 ) ) e. Word X )
82	80, 81	mpdan 421	. . . . . . . . . . . . . . . 16 |- ( x e. Word X -> ( x prefix ( (♯ ` x ) - 1 ) ) e. Word X )
83	82	adantl 277	. . . . . . . . . . . . . . 15 |- ( ( w e. Word Y /\ x e. Word X ) -> ( x prefix ( (♯ ` x ) - 1 ) ) e. Word X )
84	83	ad2antrl 490	. . . . . . . . . . . . . 14 |- ( ( m e. NN0 /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> ( x prefix ( (♯ ` x ) - 1 ) ) e. Word X )
85		simprlr 540	. . . . . . . . . . . . . . 15 |- ( ( m e. NN0 /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> x e. Word X )
86		eleq1 2294	. . . . . . . . . . . . . . . . . . . 20 |- ( (♯ ` x ) = ( m + 1 ) -> ( (♯ ` x ) e. NN <-> ( m + 1 ) e. NN ) )
87	62, 86	imbitrrid 156	. . . . . . . . . . . . . . . . . . 19 |- ( (♯ ` x ) = ( m + 1 ) -> ( m e. NN0 -> (♯ ` x ) e. NN ) )
88	87	ad2antll 491	. . . . . . . . . . . . . . . . . 18 |- ( ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) -> ( m e. NN0 -> (♯ ` x ) e. NN ) )
89	88	impcom 125	. . . . . . . . . . . . . . . . 17 |- ( ( m e. NN0 /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> (♯ ` x ) e. NN )
90	89	nnge1d 9186	. . . . . . . . . . . . . . . 16 |- ( ( m e. NN0 /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> 1 <_ (♯ ` x ) )
91		wrdlenge1n0 11151	. . . . . . . . . . . . . . . . 17 |- ( x e. Word X -> ( x =/= (/) <-> 1 <_ (♯ ` x ) ) )
92	85, 91	syl 14	. . . . . . . . . . . . . . . 16 |- ( ( m e. NN0 /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> ( x =/= (/) <-> 1 <_ (♯ ` x ) ) )
93	90, 92	mpbird 167	. . . . . . . . . . . . . . 15 |- ( ( m e. NN0 /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> x =/= (/) )
94		lswcl 11168	. . . . . . . . . . . . . . 15 |- ( ( x e. Word X /\ x =/= (/) ) -> (lastS ` x ) e. X )
95	85, 93, 94	syl2anc 411	. . . . . . . . . . . . . 14 |- ( ( m e. NN0 /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> (lastS ` x ) e. X )
96	76, 84, 95	jca32 310	. . . . . . . . . . . . 13 |- ( ( m e. NN0 /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> ( ( ( w prefix ( (♯ ` w ) - 1 ) ) e. Word Y /\ (lastS ` w ) e. Y ) /\ ( ( x prefix ( (♯ ` x ) - 1 ) ) e. Word X /\ (lastS ` x ) e. X ) ) )
97	96	adantlr 477	. . . . . . . . . . . 12 |- ( ( ( m e. NN0 /\ A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> ( ( ( w prefix ( (♯ ` w ) - 1 ) ) e. Word Y /\ (lastS ` w ) e. Y ) /\ ( ( x prefix ( (♯ ` x ) - 1 ) ) e. Word X /\ (lastS ` x ) e. X ) ) )
98		simprl 531	. . . . . . . . . . . . . 14 |- ( ( ( m e. NN0 /\ A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> ( w e. Word Y /\ x e. Word X ) )
99		simplr 529	. . . . . . . . . . . . . 14 |- ( ( ( m e. NN0 /\ A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) )
100		simprrl 541	. . . . . . . . . . . . . . . . 17 |- ( ( ( m e. NN0 /\ A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> (♯ ` x ) = (♯ ` w ) )
101	100	oveq1d 6033	. . . . . . . . . . . . . . . 16 |- ( ( ( m e. NN0 /\ A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> ( (♯ ` x ) - 1 ) = ( (♯ ` w ) - 1 ) )
102		simprlr 540	. . . . . . . . . . . . . . . . 17 |- ( ( ( m e. NN0 /\ A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> x e. Word X )
103		fzossfz 10401	. . . . . . . . . . . . . . . . . 18 |- ( 0..^ (♯ ` x ) ) C_ ( 0 ... (♯ ` x ) )
104		simprrr 542	. . . . . . . . . . . . . . . . . . . 20 |- ( ( ( m e. NN0 /\ A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> (♯ ` x ) = ( m + 1 ) )
105	62	ad2antrr 488	. . . . . . . . . . . . . . . . . . . 20 |- ( ( ( m e. NN0 /\ A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> ( m + 1 ) e. NN )
106	104, 105	eqeltrd 2308	. . . . . . . . . . . . . . . . . . 19 |- ( ( ( m e. NN0 /\ A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> (♯ ` x ) e. NN )
107		fzo0end 10469	. . . . . . . . . . . . . . . . . . 19 |- ( (♯ ` x ) e. NN -> ( (♯ ` x ) - 1 ) e. ( 0..^ (♯ ` x ) ) )
108	106, 107	syl 14	. . . . . . . . . . . . . . . . . 18 |- ( ( ( m e. NN0 /\ A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> ( (♯ ` x ) - 1 ) e. ( 0..^ (♯ ` x ) ) )
109	103, 108	sselid 3225	. . . . . . . . . . . . . . . . 17 |- ( ( ( m e. NN0 /\ A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> ( (♯ ` x ) - 1 ) e. ( 0 ... (♯ ` x ) ) )
110		pfxlen 11270	. . . . . . . . . . . . . . . . 17 |- ( ( x e. Word X /\ ( (♯ ` x ) - 1 ) e. ( 0 ... (♯ ` x ) ) ) -> (♯ ` ( x prefix ( (♯ ` x ) - 1 ) ) ) = ( (♯ ` x ) - 1 ) )
111	102, 109, 110	syl2anc 411	. . . . . . . . . . . . . . . 16 |- ( ( ( m e. NN0 /\ A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> (♯ ` ( x prefix ( (♯ ` x ) - 1 ) ) ) = ( (♯ ` x ) - 1 ) )
112		simprll 539	. . . . . . . . . . . . . . . . 17 |- ( ( ( m e. NN0 /\ A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> w e. Word Y )
113		oveq1 6025	. . . . . . . . . . . . . . . . . . . . . 22 |- ( (♯ ` w ) = (♯ ` x ) -> ( (♯ ` w ) - 1 ) = ( (♯ ` x ) - 1 ) )
114		oveq2 6026	. . . . . . . . . . . . . . . . . . . . . 22 |- ( (♯ ` w ) = (♯ ` x ) -> ( 0 ... (♯ ` w ) ) = ( 0 ... (♯ ` x ) ) )
115	113, 114	eleq12d 2302	. . . . . . . . . . . . . . . . . . . . 21 |- ( (♯ ` w ) = (♯ ` x ) -> ( ( (♯ ` w ) - 1 ) e. ( 0 ... (♯ ` w ) ) <-> ( (♯ ` x ) - 1 ) e. ( 0 ... (♯ ` x ) ) ) )
116	115	eqcoms 2234	. . . . . . . . . . . . . . . . . . . 20 |- ( (♯ ` x ) = (♯ ` w ) -> ( ( (♯ ` w ) - 1 ) e. ( 0 ... (♯ ` w ) ) <-> ( (♯ ` x ) - 1 ) e. ( 0 ... (♯ ` x ) ) ) )
117	116	adantr 276	. . . . . . . . . . . . . . . . . . 19 |- ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) -> ( ( (♯ ` w ) - 1 ) e. ( 0 ... (♯ ` w ) ) <-> ( (♯ ` x ) - 1 ) e. ( 0 ... (♯ ` x ) ) ) )
118	117	ad2antll 491	. . . . . . . . . . . . . . . . . 18 |- ( ( ( m e. NN0 /\ A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> ( ( (♯ ` w ) - 1 ) e. ( 0 ... (♯ ` w ) ) <-> ( (♯ ` x ) - 1 ) e. ( 0 ... (♯ ` x ) ) ) )
119	109, 118	mpbird 167	. . . . . . . . . . . . . . . . 17 |- ( ( ( m e. NN0 /\ A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> ( (♯ ` w ) - 1 ) e. ( 0 ... (♯ ` w ) ) )
120		pfxlen 11270	. . . . . . . . . . . . . . . . 17 |- ( ( w e. Word Y /\ ( (♯ ` w ) - 1 ) e. ( 0 ... (♯ ` w ) ) ) -> (♯ ` ( w prefix ( (♯ ` w ) - 1 ) ) ) = ( (♯ ` w ) - 1 ) )
121	112, 119, 120	syl2anc 411	. . . . . . . . . . . . . . . 16 |- ( ( ( m e. NN0 /\ A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> (♯ ` ( w prefix ( (♯ ` w ) - 1 ) ) ) = ( (♯ ` w ) - 1 ) )
122	101, 111, 121	3eqtr4d 2274	. . . . . . . . . . . . . . 15 |- ( ( ( m e. NN0 /\ A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> (♯ ` ( x prefix ( (♯ ` x ) - 1 ) ) ) = (♯ ` ( w prefix ( (♯ ` w ) - 1 ) ) ) )
123	104	oveq1d 6033	. . . . . . . . . . . . . . . 16 |- ( ( ( m e. NN0 /\ A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> ( (♯ ` x ) - 1 ) = ( ( m + 1 ) - 1 ) )
124		nn0cn 9412	. . . . . . . . . . . . . . . . . 18 |- ( m e. NN0 -> m e. CC )
125	124	ad2antrr 488	. . . . . . . . . . . . . . . . 17 |- ( ( ( m e. NN0 /\ A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> m e. CC )
126		ax-1cn 8125	. . . . . . . . . . . . . . . . 17 |- 1 e. CC
127		pncan 8385	. . . . . . . . . . . . . . . . 17 |- ( ( m e. CC /\ 1 e. CC ) -> ( ( m + 1 ) - 1 ) = m )
128	125, 126, 127	sylancl 413	. . . . . . . . . . . . . . . 16 |- ( ( ( m e. NN0 /\ A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> ( ( m + 1 ) - 1 ) = m )
129	111, 123, 128	3eqtrd 2268	. . . . . . . . . . . . . . 15 |- ( ( ( m e. NN0 /\ A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> (♯ ` ( x prefix ( (♯ ` x ) - 1 ) ) ) = m )
130	122, 129	jca 306	. . . . . . . . . . . . . 14 |- ( ( ( m e. NN0 /\ A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> ( (♯ ` ( x prefix ( (♯ ` x ) - 1 ) ) ) = (♯ ` ( w prefix ( (♯ ` w ) - 1 ) ) ) /\ (♯ ` ( x prefix ( (♯ ` x ) - 1 ) ) ) = m ) )
131	83	adantr 276	. . . . . . . . . . . . . . . 16 |- ( ( ( w e. Word Y /\ x e. Word X ) /\ u = ( w prefix ( (♯ ` w ) - 1 ) ) ) -> ( x prefix ( (♯ ` x ) - 1 ) ) e. Word X )
132		fveq2 5639	. . . . . . . . . . . . . . . . . . . . . 22 |- ( y = ( x prefix ( (♯ ` x ) - 1 ) ) -> (♯ ` y ) = (♯ ` ( x prefix ( (♯ ` x ) - 1 ) ) ) )
133		fveq2 5639	. . . . . . . . . . . . . . . . . . . . . 22 |- ( u = ( w prefix ( (♯ ` w ) - 1 ) ) -> (♯ ` u ) = (♯ ` ( w prefix ( (♯ ` w ) - 1 ) ) ) )
134	132, 133	eqeqan12d 2247	. . . . . . . . . . . . . . . . . . . . 21 |- ( ( y = ( x prefix ( (♯ ` x ) - 1 ) ) /\ u = ( w prefix ( (♯ ` w ) - 1 ) ) ) -> ( (♯ ` y ) = (♯ ` u ) <-> (♯ ` ( x prefix ( (♯ ` x ) - 1 ) ) ) = (♯ ` ( w prefix ( (♯ ` w ) - 1 ) ) ) ) )
135	134	expcom 116	. . . . . . . . . . . . . . . . . . . 20 |- ( u = ( w prefix ( (♯ ` w ) - 1 ) ) -> ( y = ( x prefix ( (♯ ` x ) - 1 ) ) -> ( (♯ ` y ) = (♯ ` u ) <-> (♯ ` ( x prefix ( (♯ ` x ) - 1 ) ) ) = (♯ ` ( w prefix ( (♯ ` w ) - 1 ) ) ) ) ) )
136	135	adantl 277	. . . . . . . . . . . . . . . . . . 19 |- ( ( ( w e. Word Y /\ x e. Word X ) /\ u = ( w prefix ( (♯ ` w ) - 1 ) ) ) -> ( y = ( x prefix ( (♯ ` x ) - 1 ) ) -> ( (♯ ` y ) = (♯ ` u ) <-> (♯ ` ( x prefix ( (♯ ` x ) - 1 ) ) ) = (♯ ` ( w prefix ( (♯ ` w ) - 1 ) ) ) ) ) )
137	136	imp 124	. . . . . . . . . . . . . . . . . 18 |- ( ( ( ( w e. Word Y /\ x e. Word X ) /\ u = ( w prefix ( (♯ ` w ) - 1 ) ) ) /\ y = ( x prefix ( (♯ ` x ) - 1 ) ) ) -> ( (♯ ` y ) = (♯ ` u ) <-> (♯ ` ( x prefix ( (♯ ` x ) - 1 ) ) ) = (♯ ` ( w prefix ( (♯ ` w ) - 1 ) ) ) ) )
138		fveqeq2 5648	. . . . . . . . . . . . . . . . . . 19 |- ( y = ( x prefix ( (♯ ` x ) - 1 ) ) -> ( (♯ ` y ) = m <-> (♯ ` ( x prefix ( (♯ ` x ) - 1 ) ) ) = m ) )
139	138	adantl 277	. . . . . . . . . . . . . . . . . 18 |- ( ( ( ( w e. Word Y /\ x e. Word X ) /\ u = ( w prefix ( (♯ ` w ) - 1 ) ) ) /\ y = ( x prefix ( (♯ ` x ) - 1 ) ) ) -> ( (♯ ` y ) = m <-> (♯ ` ( x prefix ( (♯ ` x ) - 1 ) ) ) = m ) )
140	137, 139	anbi12d 473	. . . . . . . . . . . . . . . . 17 |- ( ( ( ( w e. Word Y /\ x e. Word X ) /\ u = ( w prefix ( (♯ ` w ) - 1 ) ) ) /\ y = ( x prefix ( (♯ ` x ) - 1 ) ) ) -> ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) <-> ( (♯ ` ( x prefix ( (♯ ` x ) - 1 ) ) ) = (♯ ` ( w prefix ( (♯ ` w ) - 1 ) ) ) /\ (♯ ` ( x prefix ( (♯ ` x ) - 1 ) ) ) = m ) ) )
141		vex 2805	. . . . . . . . . . . . . . . . . . . . 21 |- y e. _V
142		vex 2805	. . . . . . . . . . . . . . . . . . . . 21 |- u e. _V
143	141, 142, 47	sbc2ie 3103	. . . . . . . . . . . . . . . . . . . 20 |- ( [. y / x ]. [. u / w ]. ph <-> ch )
144	143	bicomi 132	. . . . . . . . . . . . . . . . . . 19 |- ( ch <-> [. y / x ]. [. u / w ]. ph )
145	144	a1i 9	. . . . . . . . . . . . . . . . . 18 |- ( ( ( ( w e. Word Y /\ x e. Word X ) /\ u = ( w prefix ( (♯ ` w ) - 1 ) ) ) /\ y = ( x prefix ( (♯ ` x ) - 1 ) ) ) -> ( ch <-> [. y / x ]. [. u / w ]. ph ) )
146		simpr 110	. . . . . . . . . . . . . . . . . . 19 |- ( ( ( ( w e. Word Y /\ x e. Word X ) /\ u = ( w prefix ( (♯ ` w ) - 1 ) ) ) /\ y = ( x prefix ( (♯ ` x ) - 1 ) ) ) -> y = ( x prefix ( (♯ ` x ) - 1 ) ) )
147	146	sbceq1d 3036	. . . . . . . . . . . . . . . . . 18 |- ( ( ( ( w e. Word Y /\ x e. Word X ) /\ u = ( w prefix ( (♯ ` w ) - 1 ) ) ) /\ y = ( x prefix ( (♯ ` x ) - 1 ) ) ) -> ( [. y / x ]. [. u / w ]. ph <-> [. ( x prefix ( (♯ ` x ) - 1 ) ) / x ]. [. u / w ]. ph ) )
148		dfsbcq 3033	. . . . . . . . . . . . . . . . . . . . 21 |- ( u = ( w prefix ( (♯ ` w ) - 1 ) ) -> ( [. u / w ]. ph <-> [. ( w prefix ( (♯ ` w ) - 1 ) ) / w ]. ph ) )
149	148	sbcbidv 3090	. . . . . . . . . . . . . . . . . . . 20 |- ( u = ( w prefix ( (♯ ` w ) - 1 ) ) -> ( [. ( x prefix ( (♯ ` x ) - 1 ) ) / x ]. [. u / w ]. ph <-> [. ( x prefix ( (♯ ` x ) - 1 ) ) / x ]. [. ( w prefix ( (♯ ` w ) - 1 ) ) / w ]. ph ) )
150	149	adantl 277	. . . . . . . . . . . . . . . . . . 19 |- ( ( ( w e. Word Y /\ x e. Word X ) /\ u = ( w prefix ( (♯ ` w ) - 1 ) ) ) -> ( [. ( x prefix ( (♯ ` x ) - 1 ) ) / x ]. [. u / w ]. ph <-> [. ( x prefix ( (♯ ` x ) - 1 ) ) / x ]. [. ( w prefix ( (♯ ` w ) - 1 ) ) / w ]. ph ) )
151	150	adantr 276	. . . . . . . . . . . . . . . . . 18 |- ( ( ( ( w e. Word Y /\ x e. Word X ) /\ u = ( w prefix ( (♯ ` w ) - 1 ) ) ) /\ y = ( x prefix ( (♯ ` x ) - 1 ) ) ) -> ( [. ( x prefix ( (♯ ` x ) - 1 ) ) / x ]. [. u / w ]. ph <-> [. ( x prefix ( (♯ ` x ) - 1 ) ) / x ]. [. ( w prefix ( (♯ ` w ) - 1 ) ) / w ]. ph ) )
152	145, 147, 151	3bitrd 214	. . . . . . . . . . . . . . . . 17 |- ( ( ( ( w e. Word Y /\ x e. Word X ) /\ u = ( w prefix ( (♯ ` w ) - 1 ) ) ) /\ y = ( x prefix ( (♯ ` x ) - 1 ) ) ) -> ( ch <-> [. ( x prefix ( (♯ ` x ) - 1 ) ) / x ]. [. ( w prefix ( (♯ ` w ) - 1 ) ) / w ]. ph ) )
153	140, 152	imbi12d 234	. . . . . . . . . . . . . . . 16 |- ( ( ( ( w e. Word Y /\ x e. Word X ) /\ u = ( w prefix ( (♯ ` w ) - 1 ) ) ) /\ y = ( x prefix ( (♯ ` x ) - 1 ) ) ) -> ( ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) <-> ( ( (♯ ` ( x prefix ( (♯ ` x ) - 1 ) ) ) = (♯ ` ( w prefix ( (♯ ` w ) - 1 ) ) ) /\ (♯ ` ( x prefix ( (♯ ` x ) - 1 ) ) ) = m ) -> [. ( x prefix ( (♯ ` x ) - 1 ) ) / x ]. [. ( w prefix ( (♯ ` w ) - 1 ) ) / w ]. ph ) ) )
154	131, 153	rspcdv 2913	. . . . . . . . . . . . . . 15 |- ( ( ( w e. Word Y /\ x e. Word X ) /\ u = ( w prefix ( (♯ ` w ) - 1 ) ) ) -> ( A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) -> ( ( (♯ ` ( x prefix ( (♯ ` x ) - 1 ) ) ) = (♯ ` ( w prefix ( (♯ ` w ) - 1 ) ) ) /\ (♯ ` ( x prefix ( (♯ ` x ) - 1 ) ) ) = m ) -> [. ( x prefix ( (♯ ` x ) - 1 ) ) / x ]. [. ( w prefix ( (♯ ` w ) - 1 ) ) / w ]. ph ) ) )
155	58, 154	rspcimdv 2911	. . . . . . . . . . . . . 14 |- ( ( w e. Word Y /\ x e. Word X ) -> ( A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) -> ( ( (♯ ` ( x prefix ( (♯ ` x ) - 1 ) ) ) = (♯ ` ( w prefix ( (♯ ` w ) - 1 ) ) ) /\ (♯ ` ( x prefix ( (♯ ` x ) - 1 ) ) ) = m ) -> [. ( x prefix ( (♯ ` x ) - 1 ) ) / x ]. [. ( w prefix ( (♯ ` w ) - 1 ) ) / w ]. ph ) ) )
156	98, 99, 130, 155	syl3c 63	. . . . . . . . . . . . 13 |- ( ( ( m e. NN0 /\ A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> [. ( x prefix ( (♯ ` x ) - 1 ) ) / x ]. [. ( w prefix ( (♯ ` w ) - 1 ) ) / w ]. ph )
157	156, 122	jca 306	. . . . . . . . . . . 12 |- ( ( ( m e. NN0 /\ A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> ( [. ( x prefix ( (♯ ` x ) - 1 ) ) / x ]. [. ( w prefix ( (♯ ` w ) - 1 ) ) / w ]. ph /\ (♯ ` ( x prefix ( (♯ ` x ) - 1 ) ) ) = (♯ ` ( w prefix ( (♯ ` w ) - 1 ) ) ) ) )
158		dfsbcq 3033	. . . . . . . . . . . . . . . 16 |- ( u = ( w prefix ( (♯ ` w ) - 1 ) ) -> ( [. u / w ]. [. y / x ]. ph <-> [. ( w prefix ( (♯ ` w ) - 1 ) ) / w ]. [. y / x ]. ph ) )
159		sbccom 3107	. . . . . . . . . . . . . . . 16 |- ( [. ( w prefix ( (♯ ` w ) - 1 ) ) / w ]. [. y / x ]. ph <-> [. y / x ]. [. ( w prefix ( (♯ ` w ) - 1 ) ) / w ]. ph )
160	158, 159	bitrdi 196	. . . . . . . . . . . . . . 15 |- ( u = ( w prefix ( (♯ ` w ) - 1 ) ) -> ( [. u / w ]. [. y / x ]. ph <-> [. y / x ]. [. ( w prefix ( (♯ ` w ) - 1 ) ) / w ]. ph ) )
161	133	eqeq2d 2243	. . . . . . . . . . . . . . 15 |- ( u = ( w prefix ( (♯ ` w ) - 1 ) ) -> ( (♯ ` y ) = (♯ ` u ) <-> (♯ ` y ) = (♯ ` ( w prefix ( (♯ ` w ) - 1 ) ) ) ) )
162	160, 161	anbi12d 473	. . . . . . . . . . . . . 14 |- ( u = ( w prefix ( (♯ ` w ) - 1 ) ) -> ( ( [. u / w ]. [. y / x ]. ph /\ (♯ ` y ) = (♯ ` u ) ) <-> ( [. y / x ]. [. ( w prefix ( (♯ ` w ) - 1 ) ) / w ]. ph /\ (♯ ` y ) = (♯ ` ( w prefix ( (♯ ` w ) - 1 ) ) ) ) ) )
163		oveq1 6025	. . . . . . . . . . . . . . 15 |- ( u = ( w prefix ( (♯ ` w ) - 1 ) ) -> ( u ++ <" s "> ) = ( ( w prefix ( (♯ ` w ) - 1 ) ) ++ <" s "> ) )
164	163	sbceq1d 3036	. . . . . . . . . . . . . 14 |- ( u = ( w prefix ( (♯ ` w ) - 1 ) ) -> ( [. ( u ++ <" s "> ) / w ]. [. ( y ++ <" z "> ) / x ]. ph <-> [. ( ( w prefix ( (♯ ` w ) - 1 ) ) ++ <" s "> ) / w ]. [. ( y ++ <" z "> ) / x ]. ph ) )
165	162, 164	imbi12d 234	. . . . . . . . . . . . 13 |- ( u = ( w prefix ( (♯ ` w ) - 1 ) ) -> ( ( ( [. u / w ]. [. y / x ]. ph /\ (♯ ` y ) = (♯ ` u ) ) -> [. ( u ++ <" s "> ) / w ]. [. ( y ++ <" z "> ) / x ]. ph ) <-> ( ( [. y / x ]. [. ( w prefix ( (♯ ` w ) - 1 ) ) / w ]. ph /\ (♯ ` y ) = (♯ ` ( w prefix ( (♯ ` w ) - 1 ) ) ) ) -> [. ( ( w prefix ( (♯ ` w ) - 1 ) ) ++ <" s "> ) / w ]. [. ( y ++ <" z "> ) / x ]. ph ) ) )
166		s1eq 11200	. . . . . . . . . . . . . . . . 17 |- ( s = (lastS ` w ) -> <" s "> = <" (lastS ` w ) "> )
167	166	oveq2d 6034	. . . . . . . . . . . . . . . 16 |- ( s = (lastS ` w ) -> ( ( w prefix ( (♯ ` w ) - 1 ) ) ++ <" s "> ) = ( ( w prefix ( (♯ ` w ) - 1 ) ) ++ <" (lastS ` w ) "> ) )
168	167	sbceq1d 3036	. . . . . . . . . . . . . . 15 |- ( s = (lastS ` w ) -> ( [. ( ( w prefix ( (♯ ` w ) - 1 ) ) ++ <" s "> ) / w ]. [. ( y ++ <" z "> ) / x ]. ph <-> [. ( ( w prefix ( (♯ ` w ) - 1 ) ) ++ <" (lastS ` w ) "> ) / w ]. [. ( y ++ <" z "> ) / x ]. ph ) )
169	168	imbi2d 230	. . . . . . . . . . . . . 14 |- ( s = (lastS ` w ) -> ( ( ( [. y / x ]. [. ( w prefix ( (♯ ` w ) - 1 ) ) / w ]. ph /\ (♯ ` y ) = (♯ ` ( w prefix ( (♯ ` w ) - 1 ) ) ) ) -> [. ( ( w prefix ( (♯ ` w ) - 1 ) ) ++ <" s "> ) / w ]. [. ( y ++ <" z "> ) / x ]. ph ) <-> ( ( [. y / x ]. [. ( w prefix ( (♯ ` w ) - 1 ) ) / w ]. ph /\ (♯ ` y ) = (♯ ` ( w prefix ( (♯ ` w ) - 1 ) ) ) ) -> [. ( ( w prefix ( (♯ ` w ) - 1 ) ) ++ <" (lastS ` w ) "> ) / w ]. [. ( y ++ <" z "> ) / x ]. ph ) ) )
170		sbccom 3107	. . . . . . . . . . . . . . . 16 |- ( [. ( ( w prefix ( (♯ ` w ) - 1 ) ) ++ <" (lastS ` w ) "> ) / w ]. [. ( y ++ <" z "> ) / x ]. ph <-> [. ( y ++ <" z "> ) / x ]. [. ( ( w prefix ( (♯ ` w ) - 1 ) ) ++ <" (lastS ` w ) "> ) / w ]. ph )
171	170	a1i 9	. . . . . . . . . . . . . . 15 |- ( s = (lastS ` w ) -> ( [. ( ( w prefix ( (♯ ` w ) - 1 ) ) ++ <" (lastS ` w ) "> ) / w ]. [. ( y ++ <" z "> ) / x ]. ph <-> [. ( y ++ <" z "> ) / x ]. [. ( ( w prefix ( (♯ ` w ) - 1 ) ) ++ <" (lastS ` w ) "> ) / w ]. ph ) )
172	171	imbi2d 230	. . . . . . . . . . . . . 14 |- ( s = (lastS ` w ) -> ( ( ( [. y / x ]. [. ( w prefix ( (♯ ` w ) - 1 ) ) / w ]. ph /\ (♯ ` y ) = (♯ ` ( w prefix ( (♯ ` w ) - 1 ) ) ) ) -> [. ( ( w prefix ( (♯ ` w ) - 1 ) ) ++ <" (lastS ` w ) "> ) / w ]. [. ( y ++ <" z "> ) / x ]. ph ) <-> ( ( [. y / x ]. [. ( w prefix ( (♯ ` w ) - 1 ) ) / w ]. ph /\ (♯ ` y ) = (♯ ` ( w prefix ( (♯ ` w ) - 1 ) ) ) ) -> [. ( y ++ <" z "> ) / x ]. [. ( ( w prefix ( (♯ ` w ) - 1 ) ) ++ <" (lastS ` w ) "> ) / w ]. ph ) ) )
173	169, 172	bitrd 188	. . . . . . . . . . . . 13 |- ( s = (lastS ` w ) -> ( ( ( [. y / x ]. [. ( w prefix ( (♯ ` w ) - 1 ) ) / w ]. ph /\ (♯ ` y ) = (♯ ` ( w prefix ( (♯ ` w ) - 1 ) ) ) ) -> [. ( ( w prefix ( (♯ ` w ) - 1 ) ) ++ <" s "> ) / w ]. [. ( y ++ <" z "> ) / x ]. ph ) <-> ( ( [. y / x ]. [. ( w prefix ( (♯ ` w ) - 1 ) ) / w ]. ph /\ (♯ ` y ) = (♯ ` ( w prefix ( (♯ ` w ) - 1 ) ) ) ) -> [. ( y ++ <" z "> ) / x ]. [. ( ( w prefix ( (♯ ` w ) - 1 ) ) ++ <" (lastS ` w ) "> ) / w ]. ph ) ) )
174		dfsbcq 3033	. . . . . . . . . . . . . . 15 |- ( y = ( x prefix ( (♯ ` x ) - 1 ) ) -> ( [. y / x ]. [. ( w prefix ( (♯ ` w ) - 1 ) ) / w ]. ph <-> [. ( x prefix ( (♯ ` x ) - 1 ) ) / x ]. [. ( w prefix ( (♯ ` w ) - 1 ) ) / w ]. ph ) )
175		fveqeq2 5648	. . . . . . . . . . . . . . 15 |- ( y = ( x prefix ( (♯ ` x ) - 1 ) ) -> ( (♯ ` y ) = (♯ ` ( w prefix ( (♯ ` w ) - 1 ) ) ) <-> (♯ ` ( x prefix ( (♯ ` x ) - 1 ) ) ) = (♯ ` ( w prefix ( (♯ ` w ) - 1 ) ) ) ) )
176	174, 175	anbi12d 473	. . . . . . . . . . . . . 14 |- ( y = ( x prefix ( (♯ ` x ) - 1 ) ) -> ( ( [. y / x ]. [. ( w prefix ( (♯ ` w ) - 1 ) ) / w ]. ph /\ (♯ ` y ) = (♯ ` ( w prefix ( (♯ ` w ) - 1 ) ) ) ) <-> ( [. ( x prefix ( (♯ ` x ) - 1 ) ) / x ]. [. ( w prefix ( (♯ ` w ) - 1 ) ) / w ]. ph /\ (♯ ` ( x prefix ( (♯ ` x ) - 1 ) ) ) = (♯ ` ( w prefix ( (♯ ` w ) - 1 ) ) ) ) ) )
177		oveq1 6025	. . . . . . . . . . . . . . 15 |- ( y = ( x prefix ( (♯ ` x ) - 1 ) ) -> ( y ++ <" z "> ) = ( ( x prefix ( (♯ ` x ) - 1 ) ) ++ <" z "> ) )
178	177	sbceq1d 3036	. . . . . . . . . . . . . 14 |- ( y = ( x prefix ( (♯ ` x ) - 1 ) ) -> ( [. ( y ++ <" z "> ) / x ]. [. ( ( w prefix ( (♯ ` w ) - 1 ) ) ++ <" (lastS ` w ) "> ) / w ]. ph <-> [. ( ( x prefix ( (♯ ` x ) - 1 ) ) ++ <" z "> ) / x ]. [. ( ( w prefix ( (♯ ` w ) - 1 ) ) ++ <" (lastS ` w ) "> ) / w ]. ph ) )
179	176, 178	imbi12d 234	. . . . . . . . . . . . 13 |- ( y = ( x prefix ( (♯ ` x ) - 1 ) ) -> ( ( ( [. y / x ]. [. ( w prefix ( (♯ ` w ) - 1 ) ) / w ]. ph /\ (♯ ` y ) = (♯ ` ( w prefix ( (♯ ` w ) - 1 ) ) ) ) -> [. ( y ++ <" z "> ) / x ]. [. ( ( w prefix ( (♯ ` w ) - 1 ) ) ++ <" (lastS ` w ) "> ) / w ]. ph ) <-> ( ( [. ( x prefix ( (♯ ` x ) - 1 ) ) / x ]. [. ( w prefix ( (♯ ` w ) - 1 ) ) / w ]. ph /\ (♯ ` ( x prefix ( (♯ ` x ) - 1 ) ) ) = (♯ ` ( w prefix ( (♯ ` w ) - 1 ) ) ) ) -> [. ( ( x prefix ( (♯ ` x ) - 1 ) ) ++ <" z "> ) / x ]. [. ( ( w prefix ( (♯ ` w ) - 1 ) ) ++ <" (lastS ` w ) "> ) / w ]. ph ) ) )
180		s1eq 11200	. . . . . . . . . . . . . . . 16 |- ( z = (lastS ` x ) -> <" z "> = <" (lastS ` x ) "> )
181	180	oveq2d 6034	. . . . . . . . . . . . . . 15 |- ( z = (lastS ` x ) -> ( ( x prefix ( (♯ ` x ) - 1 ) ) ++ <" z "> ) = ( ( x prefix ( (♯ ` x ) - 1 ) ) ++ <" (lastS ` x ) "> ) )
182	181	sbceq1d 3036	. . . . . . . . . . . . . 14 |- ( z = (lastS ` x ) -> ( [. ( ( x prefix ( (♯ ` x ) - 1 ) ) ++ <" z "> ) / x ]. [. ( ( w prefix ( (♯ ` w ) - 1 ) ) ++ <" (lastS ` w ) "> ) / w ]. ph <-> [. ( ( x prefix ( (♯ ` x ) - 1 ) ) ++ <" (lastS ` x ) "> ) / x ]. [. ( ( w prefix ( (♯ ` w ) - 1 ) ) ++ <" (lastS ` w ) "> ) / w ]. ph ) )
183	182	imbi2d 230	. . . . . . . . . . . . 13 |- ( z = (lastS ` x ) -> ( ( ( [. ( x prefix ( (♯ ` x ) - 1 ) ) / x ]. [. ( w prefix ( (♯ ` w ) - 1 ) ) / w ]. ph /\ (♯ ` ( x prefix ( (♯ ` x ) - 1 ) ) ) = (♯ ` ( w prefix ( (♯ ` w ) - 1 ) ) ) ) -> [. ( ( x prefix ( (♯ ` x ) - 1 ) ) ++ <" z "> ) / x ]. [. ( ( w prefix ( (♯ ` w ) - 1 ) ) ++ <" (lastS ` w ) "> ) / w ]. ph ) <-> ( ( [. ( x prefix ( (♯ ` x ) - 1 ) ) / x ]. [. ( w prefix ( (♯ ` w ) - 1 ) ) / w ]. ph /\ (♯ ` ( x prefix ( (♯ ` x ) - 1 ) ) ) = (♯ ` ( w prefix ( (♯ ` w ) - 1 ) ) ) ) -> [. ( ( x prefix ( (♯ ` x ) - 1 ) ) ++ <" (lastS ` x ) "> ) / x ]. [. ( ( w prefix ( (♯ ` w ) - 1 ) ) ++ <" (lastS ` w ) "> ) / w ]. ph ) ) )
184		simplr 529	. . . . . . . . . . . . . . . . 17 |- ( ( ( ( u e. Word Y /\ s e. Y ) /\ ( y e. Word X /\ z e. X ) ) /\ (♯ ` y ) = (♯ ` u ) ) -> ( y e. Word X /\ z e. X ) )
185		simpll 527	. . . . . . . . . . . . . . . . 17 |- ( ( ( ( u e. Word Y /\ s e. Y ) /\ ( y e. Word X /\ z e. X ) ) /\ (♯ ` y ) = (♯ ` u ) ) -> ( u e. Word Y /\ s e. Y ) )
186		simpr 110	. . . . . . . . . . . . . . . . 17 |- ( ( ( ( u e. Word Y /\ s e. Y ) /\ ( y e. Word X /\ z e. X ) ) /\ (♯ ` y ) = (♯ ` u ) ) -> (♯ ` y ) = (♯ ` u ) )
187		wrd2ind.7	. . . . . . . . . . . . . . . . 17 |- ( ( ( y e. Word X /\ z e. X ) /\ ( u e. Word Y /\ s e. Y ) /\ (♯ ` y ) = (♯ ` u ) ) -> ( ch -> th ) )
188	184, 185, 186, 187	syl3anc 1273	. . . . . . . . . . . . . . . 16 |- ( ( ( ( u e. Word Y /\ s e. Y ) /\ ( y e. Word X /\ z e. X ) ) /\ (♯ ` y ) = (♯ ` u ) ) -> ( ch -> th ) )
189	47	ancoms 268	. . . . . . . . . . . . . . . . . 18 |- ( ( w = u /\ x = y ) -> ( ph <-> ch ) )
190	142, 141, 189	sbc2ie 3103	. . . . . . . . . . . . . . . . 17 |- ( [. u / w ]. [. y / x ]. ph <-> ch )
191	190	a1i 9	. . . . . . . . . . . . . . . 16 |- ( ( ( ( u e. Word Y /\ s e. Y ) /\ ( y e. Word X /\ z e. X ) ) /\ (♯ ` y ) = (♯ ` u ) ) -> ( [. u / w ]. [. y / x ]. ph <-> ch ) )
192		ccatws1cl 11213	. . . . . . . . . . . . . . . . . 18 |- ( ( u e. Word Y /\ s e. Y ) -> ( u ++ <" s "> ) e. Word Y )
193	192	ad2antrr 488	. . . . . . . . . . . . . . . . 17 |- ( ( ( ( u e. Word Y /\ s e. Y ) /\ ( y e. Word X /\ z e. X ) ) /\ (♯ ` y ) = (♯ ` u ) ) -> ( u ++ <" s "> ) e. Word Y )
194		ccatws1cl 11213	. . . . . . . . . . . . . . . . . 18 |- ( ( y e. Word X /\ z e. X ) -> ( y ++ <" z "> ) e. Word X )
195	184, 194	syl 14	. . . . . . . . . . . . . . . . 17 |- ( ( ( ( u e. Word Y /\ s e. Y ) /\ ( y e. Word X /\ z e. X ) ) /\ (♯ ` y ) = (♯ ` u ) ) -> ( y ++ <" z "> ) e. Word X )
196		nfv 1576	. . . . . . . . . . . . . . . . . 18 |- F/ w th
197		nfv 1576	. . . . . . . . . . . . . . . . . 18 |- F/ x th
198		nfv 1576	. . . . . . . . . . . . . . . . . 18 |- F/ w ( y ++ <" z "> ) e. Word X
199		wrd2ind.3	. . . . . . . . . . . . . . . . . . 19 |- ( ( x = ( y ++ <" z "> ) /\ w = ( u ++ <" s "> ) ) -> ( ph <-> th ) )
200	199	ancoms 268	. . . . . . . . . . . . . . . . . 18 |- ( ( w = ( u ++ <" s "> ) /\ x = ( y ++ <" z "> ) ) -> ( ph <-> th ) )
201	196, 197, 198, 200	sbc2iegf 3102	. . . . . . . . . . . . . . . . 17 |- ( ( ( u ++ <" s "> ) e. Word Y /\ ( y ++ <" z "> ) e. Word X ) -> ( [. ( u ++ <" s "> ) / w ]. [. ( y ++ <" z "> ) / x ]. ph <-> th ) )
202	193, 195, 201	syl2anc 411	. . . . . . . . . . . . . . . 16 |- ( ( ( ( u e. Word Y /\ s e. Y ) /\ ( y e. Word X /\ z e. X ) ) /\ (♯ ` y ) = (♯ ` u ) ) -> ( [. ( u ++ <" s "> ) / w ]. [. ( y ++ <" z "> ) / x ]. ph <-> th ) )
203	188, 191, 202	3imtr4d 203	. . . . . . . . . . . . . . 15 |- ( ( ( ( u e. Word Y /\ s e. Y ) /\ ( y e. Word X /\ z e. X ) ) /\ (♯ ` y ) = (♯ ` u ) ) -> ( [. u / w ]. [. y / x ]. ph -> [. ( u ++ <" s "> ) / w ]. [. ( y ++ <" z "> ) / x ]. ph ) )
204	203	ex 115	. . . . . . . . . . . . . 14 |- ( ( ( u e. Word Y /\ s e. Y ) /\ ( y e. Word X /\ z e. X ) ) -> ( (♯ ` y ) = (♯ ` u ) -> ( [. u / w ]. [. y / x ]. ph -> [. ( u ++ <" s "> ) / w ]. [. ( y ++ <" z "> ) / x ]. ph ) ) )
205	204	impcomd 255	. . . . . . . . . . . . 13 |- ( ( ( u e. Word Y /\ s e. Y ) /\ ( y e. Word X /\ z e. X ) ) -> ( ( [. u / w ]. [. y / x ]. ph /\ (♯ ` y ) = (♯ ` u ) ) -> [. ( u ++ <" s "> ) / w ]. [. ( y ++ <" z "> ) / x ]. ph ) )
206	165, 173, 179, 183, 205	vtocl4ga 2876	. . . . . . . . . . . 12 |- ( ( ( ( w prefix ( (♯ ` w ) - 1 ) ) e. Word Y /\ (lastS ` w ) e. Y ) /\ ( ( x prefix ( (♯ ` x ) - 1 ) ) e. Word X /\ (lastS ` x ) e. X ) ) -> ( ( [. ( x prefix ( (♯ ` x ) - 1 ) ) / x ]. [. ( w prefix ( (♯ ` w ) - 1 ) ) / w ]. ph /\ (♯ ` ( x prefix ( (♯ ` x ) - 1 ) ) ) = (♯ ` ( w prefix ( (♯ ` w ) - 1 ) ) ) ) -> [. ( ( x prefix ( (♯ ` x ) - 1 ) ) ++ <" (lastS ` x ) "> ) / x ]. [. ( ( w prefix ( (♯ ` w ) - 1 ) ) ++ <" (lastS ` w ) "> ) / w ]. ph ) )
207	97, 157, 206	sylc 62	. . . . . . . . . . 11 |- ( ( ( m e. NN0 /\ A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> [. ( ( x prefix ( (♯ ` x ) - 1 ) ) ++ <" (lastS ` x ) "> ) / x ]. [. ( ( w prefix ( (♯ ` w ) - 1 ) ) ++ <" (lastS ` w ) "> ) / w ]. ph )
208		eqtr2 2250	. . . . . . . . . . . . . . . 16 |- ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) -> (♯ ` w ) = ( m + 1 ) )
209	208	ad2antll 491	. . . . . . . . . . . . . . 15 |- ( ( ( m e. NN0 /\ A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> (♯ ` w ) = ( m + 1 ) )
210	209, 105	eqeltrd 2308	. . . . . . . . . . . . . 14 |- ( ( ( m e. NN0 /\ A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> (♯ ` w ) e. NN )
211	21	adantr 276	. . . . . . . . . . . . . . . 16 |- ( ( w e. Word Y /\ x e. Word X ) -> w e. Fin )
212	211	ad2antrl 490	. . . . . . . . . . . . . . 15 |- ( ( ( m e. NN0 /\ A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> w e. Fin )
213		hashnncl 11058	. . . . . . . . . . . . . . 15 |- ( w e. Fin -> ( (♯ ` w ) e. NN <-> w =/= (/) ) )
214	212, 213	syl 14	. . . . . . . . . . . . . 14 |- ( ( ( m e. NN0 /\ A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> ( (♯ ` w ) e. NN <-> w =/= (/) ) )
215	210, 214	mpbid 147	. . . . . . . . . . . . 13 |- ( ( ( m e. NN0 /\ A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> w =/= (/) )
216		pfxlswccat 11298	. . . . . . . . . . . . . 14 |- ( ( w e. Word Y /\ w =/= (/) ) -> ( ( w prefix ( (♯ ` w ) - 1 ) ) ++ <" (lastS ` w ) "> ) = w )
217	216	eqcomd 2237	. . . . . . . . . . . . 13 |- ( ( w e. Word Y /\ w =/= (/) ) -> w = ( ( w prefix ( (♯ ` w ) - 1 ) ) ++ <" (lastS ` w ) "> ) )
218	112, 215, 217	syl2anc 411	. . . . . . . . . . . 12 |- ( ( ( m e. NN0 /\ A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> w = ( ( w prefix ( (♯ ` w ) - 1 ) ) ++ <" (lastS ` w ) "> ) )
219	25	adantl 277	. . . . . . . . . . . . . . . 16 |- ( ( w e. Word Y /\ x e. Word X ) -> x e. Fin )
220	219	ad2antrl 490	. . . . . . . . . . . . . . 15 |- ( ( ( m e. NN0 /\ A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> x e. Fin )
221		hashnncl 11058	. . . . . . . . . . . . . . 15 |- ( x e. Fin -> ( (♯ ` x ) e. NN <-> x =/= (/) ) )
222	220, 221	syl 14	. . . . . . . . . . . . . 14 |- ( ( ( m e. NN0 /\ A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> ( (♯ ` x ) e. NN <-> x =/= (/) ) )
223	106, 222	mpbid 147	. . . . . . . . . . . . 13 |- ( ( ( m e. NN0 /\ A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> x =/= (/) )
224		pfxlswccat 11298	. . . . . . . . . . . . . 14 |- ( ( x e. Word X /\ x =/= (/) ) -> ( ( x prefix ( (♯ ` x ) - 1 ) ) ++ <" (lastS ` x ) "> ) = x )
225	224	eqcomd 2237	. . . . . . . . . . . . 13 |- ( ( x e. Word X /\ x =/= (/) ) -> x = ( ( x prefix ( (♯ ` x ) - 1 ) ) ++ <" (lastS ` x ) "> ) )
226	102, 223, 225	syl2anc 411	. . . . . . . . . . . 12 |- ( ( ( m e. NN0 /\ A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> x = ( ( x prefix ( (♯ ` x ) - 1 ) ) ++ <" (lastS ` x ) "> ) )
227		sbceq1a 3041	. . . . . . . . . . . . 13 |- ( w = ( ( w prefix ( (♯ ` w ) - 1 ) ) ++ <" (lastS ` w ) "> ) -> ( ph <-> [. ( ( w prefix ( (♯ ` w ) - 1 ) ) ++ <" (lastS ` w ) "> ) / w ]. ph ) )
228		sbceq1a 3041	. . . . . . . . . . . . 13 |- ( x = ( ( x prefix ( (♯ ` x ) - 1 ) ) ++ <" (lastS ` x ) "> ) -> ( [. ( ( w prefix ( (♯ ` w ) - 1 ) ) ++ <" (lastS ` w ) "> ) / w ]. ph <-> [. ( ( x prefix ( (♯ ` x ) - 1 ) ) ++ <" (lastS ` x ) "> ) / x ]. [. ( ( w prefix ( (♯ ` w ) - 1 ) ) ++ <" (lastS ` w ) "> ) / w ]. ph ) )
229	227, 228	sylan9bb 462	. . . . . . . . . . . 12 |- ( ( w = ( ( w prefix ( (♯ ` w ) - 1 ) ) ++ <" (lastS ` w ) "> ) /\ x = ( ( x prefix ( (♯ ` x ) - 1 ) ) ++ <" (lastS ` x ) "> ) ) -> ( ph <-> [. ( ( x prefix ( (♯ ` x ) - 1 ) ) ++ <" (lastS ` x ) "> ) / x ]. [. ( ( w prefix ( (♯ ` w ) - 1 ) ) ++ <" (lastS ` w ) "> ) / w ]. ph ) )
230	218, 226, 229	syl2anc 411	. . . . . . . . . . 11 |- ( ( ( m e. NN0 /\ A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> ( ph <-> [. ( ( x prefix ( (♯ ` x ) - 1 ) ) ++ <" (lastS ` x ) "> ) / x ]. [. ( ( w prefix ( (♯ ` w ) - 1 ) ) ++ <" (lastS ` w ) "> ) / w ]. ph ) )
231	207, 230	mpbird 167	. . . . . . . . . 10 |- ( ( ( m e. NN0 /\ A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) /\ ( ( w e. Word Y /\ x e. Word X ) /\ ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) ) ) -> ph )
232	231	expr 375	. . . . . . . . 9 |- ( ( ( m e. NN0 /\ A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) /\ ( w e. Word Y /\ x e. Word X ) ) -> ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) -> ph ) )
233	232	ralrimivva 2614	. . . . . . . 8 |- ( ( m e. NN0 /\ A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) ) -> A. w e. Word Y A. x e. Word X ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) -> ph ) )
234	233	ex 115	. . . . . . 7 |- ( m e. NN0 -> ( A. u e. Word Y A. y e. Word X ( ( (♯ ` y ) = (♯ ` u ) /\ (♯ ` y ) = m ) -> ch ) -> A. w e. Word Y A. x e. Word X ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) -> ph ) ) )
235	51, 234	biimtrid 152	. . . . . 6 |- ( m e. NN0 -> ( A. w e. Word Y A. x e. Word X ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = m ) -> ph ) -> A. w e. Word Y A. x e. Word X ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = ( m + 1 ) ) -> ph ) ) )
236	5, 9, 13, 17, 40, 235	nn0ind 9594	. . . . 5 |- ( (♯ ` A ) e. NN0 -> A. w e. Word Y A. x e. Word X ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = (♯ ` A ) ) -> ph ) )
237	1, 236	syl 14	. . . 4 |- ( A e. Word X -> A. w e. Word Y A. x e. Word X ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = (♯ ` A ) ) -> ph ) )
238	237	3ad2ant1 1044	. . 3 |- ( ( A e. Word X /\ B e. Word Y /\ (♯ ` A ) = (♯ ` B ) ) -> A. w e. Word Y A. x e. Word X ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = (♯ ` A ) ) -> ph ) )
239		fveq2 5639	. . . . . . . . 9 |- ( w = B -> (♯ ` w ) = (♯ ` B ) )
240	239	eqeq2d 2243	. . . . . . . 8 |- ( w = B -> ( (♯ ` x ) = (♯ ` w ) <-> (♯ ` x ) = (♯ ` B ) ) )
241	240	anbi1d 465	. . . . . . 7 |- ( w = B -> ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = (♯ ` A ) ) <-> ( (♯ ` x ) = (♯ ` B ) /\ (♯ ` x ) = (♯ ` A ) ) ) )
242		wrd2ind.5	. . . . . . 7 |- ( w = B -> ( ph <-> rh ) )
243	241, 242	imbi12d 234	. . . . . 6 |- ( w = B -> ( ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = (♯ ` A ) ) -> ph ) <-> ( ( (♯ ` x ) = (♯ ` B ) /\ (♯ ` x ) = (♯ ` A ) ) -> rh ) ) )
244	243	ralbidv 2532	. . . . 5 |- ( w = B -> ( A. x e. Word X ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = (♯ ` A ) ) -> ph ) <-> A. x e. Word X ( ( (♯ ` x ) = (♯ ` B ) /\ (♯ ` x ) = (♯ ` A ) ) -> rh ) ) )
245	244	rspcv 2906	. . . 4 |- ( B e. Word Y -> ( A. w e. Word Y A. x e. Word X ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = (♯ ` A ) ) -> ph ) -> A. x e. Word X ( ( (♯ ` x ) = (♯ ` B ) /\ (♯ ` x ) = (♯ ` A ) ) -> rh ) ) )
246	245	3ad2ant2 1045	. . 3 |- ( ( A e. Word X /\ B e. Word Y /\ (♯ ` A ) = (♯ ` B ) ) -> ( A. w e. Word Y A. x e. Word X ( ( (♯ ` x ) = (♯ ` w ) /\ (♯ ` x ) = (♯ ` A ) ) -> ph ) -> A. x e. Word X ( ( (♯ ` x ) = (♯ ` B ) /\ (♯ ` x ) = (♯ ` A ) ) -> rh ) ) )
247	238, 246	mpd 13	. 2 |- ( ( A e. Word X /\ B e. Word Y /\ (♯ ` A ) = (♯ ` B ) ) -> A. x e. Word X ( ( (♯ ` x ) = (♯ ` B ) /\ (♯ ` x ) = (♯ ` A ) ) -> rh ) )
248		eqidd 2232	. 2 |- ( ( A e. Word X /\ B e. Word Y /\ (♯ ` A ) = (♯ ` B ) ) -> (♯ ` A ) = (♯ ` A ) )
249		fveqeq2 5648	. . . . . . . . . 10 |- ( x = A -> ( (♯ ` x ) = (♯ ` B ) <-> (♯ ` A ) = (♯ ` B ) ) )
250		fveqeq2 5648	. . . . . . . . . 10 |- ( x = A -> ( (♯ ` x ) = (♯ ` A ) <-> (♯ ` A ) = (♯ ` A ) ) )
251	249, 250	anbi12d 473	. . . . . . . . 9 |- ( x = A -> ( ( (♯ ` x ) = (♯ ` B ) /\ (♯ ` x ) = (♯ ` A ) ) <-> ( (♯ ` A ) = (♯ ` B ) /\ (♯ ` A ) = (♯ ` A ) ) ) )
252		wrd2ind.4	. . . . . . . . 9 |- ( x = A -> ( rh <-> ta ) )
253	251, 252	imbi12d 234	. . . . . . . 8 |- ( x = A -> ( ( ( (♯ ` x ) = (♯ ` B ) /\ (♯ ` x ) = (♯ ` A ) ) -> rh ) <-> ( ( (♯ ` A ) = (♯ ` B ) /\ (♯ ` A ) = (♯ ` A ) ) -> ta ) ) )
254	253	rspcv 2906	. . . . . . 7 |- ( A e. Word X -> ( A. x e. Word X ( ( (♯ ` x ) = (♯ ` B ) /\ (♯ ` x ) = (♯ ` A ) ) -> rh ) -> ( ( (♯ ` A ) = (♯ ` B ) /\ (♯ ` A ) = (♯ ` A ) ) -> ta ) ) )
255	254	com23 78	. . . . . 6 |- ( A e. Word X -> ( ( (♯ ` A ) = (♯ ` B ) /\ (♯ ` A ) = (♯ ` A ) ) -> ( A. x e. Word X ( ( (♯ ` x ) = (♯ ` B ) /\ (♯ ` x ) = (♯ ` A ) ) -> rh ) -> ta ) ) )
256	255	expd 258	. . . . 5 |- ( A e. Word X -> ( (♯ ` A ) = (♯ ` B ) -> ( (♯ ` A ) = (♯ ` A ) -> ( A. x e. Word X ( ( (♯ ` x ) = (♯ ` B ) /\ (♯ ` x ) = (♯ ` A ) ) -> rh ) -> ta ) ) ) )
257	256	com34 83	. . . 4 |- ( A e. Word X -> ( (♯ ` A ) = (♯ ` B ) -> ( A. x e. Word X ( ( (♯ ` x ) = (♯ ` B ) /\ (♯ ` x ) = (♯ ` A ) ) -> rh ) -> ( (♯ ` A ) = (♯ ` A ) -> ta ) ) ) )
258	257	imp 124	. . 3 |- ( ( A e. Word X /\ (♯ ` A ) = (♯ ` B ) ) -> ( A. x e. Word X ( ( (♯ ` x ) = (♯ ` B ) /\ (♯ ` x ) = (♯ ` A ) ) -> rh ) -> ( (♯ ` A ) = (♯ ` A ) -> ta ) ) )
259	258	3adant2 1042	. 2 |- ( ( A e. Word X /\ B e. Word Y /\ (♯ ` A ) = (♯ ` B ) ) -> ( A. x e. Word X ( ( (♯ ` x ) = (♯ ` B ) /\ (♯ ` x ) = (♯ ` A ) ) -> rh ) -> ( (♯ ` A ) = (♯ ` A ) -> ta ) ) )
260	247, 248, 259	mp2d 47	1 |- ( ( A e. Word X /\ B e. Word Y /\ (♯ ` A ) = (♯ ` B ) ) -> ta )

Syntax hints:   -> wi 4   /\ wa 104   <-> wb 105   /\ w3a 1004   = wceq 1397   e. wcel 2202   =/= wne 2402   A.wral 2510   [.wsbc 3031   (/)c0 3494   class class class wbr 4088   ` cfv 5326  (class class class)co 6018   Fincfn 6909   CCcc 8030   0cc0 8032   1c1 8033   + caddc 8035   <_ cle 8215   - cmin 8350   NNcn 9143   NN0cn0 9402   ZZcz 9479   ...cfz 10243  ..^cfzo 10377  ♯chash 11038  Word cword 11117  lastSclsw 11162   ++ cconcat 11171   <"cs1 11196   prefix cpfx 11257

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-in1 619  ax-in2 620  ax-io 716  ax-5 1495  ax-7 1496  ax-gen 1497  ax-ie1 1541  ax-ie2 1542  ax-8 1552  ax-10 1553  ax-11 1554  ax-i12 1555  ax-bndl 1557  ax-4 1558  ax-17 1574  ax-i9 1578  ax-ial 1582  ax-i5r 1583  ax-13 2204  ax-14 2205  ax-ext 2213  ax-coll 4204  ax-sep 4207  ax-nul 4215  ax-pow 4264  ax-pr 4299  ax-un 4530  ax-setind 4635  ax-iinf 4686  ax-cnex 8123  ax-resscn 8124  ax-1cn 8125  ax-1re 8126  ax-icn 8127  ax-addcl 8128  ax-addrcl 8129  ax-mulcl 8130  ax-mulrcl 8131  ax-addcom 8132  ax-mulcom 8133  ax-addass 8134  ax-mulass 8135  ax-distr 8136  ax-i2m1 8137  ax-0lt1 8138  ax-1rid 8139  ax-0id 8140  ax-rnegex 8141  ax-precex 8142  ax-cnre 8143  ax-pre-ltirr 8144  ax-pre-ltwlin 8145  ax-pre-lttrn 8146  ax-pre-apti 8147  ax-pre-ltadd 8148  ax-pre-mulgt0 8149

This theorem depends on definitions:  df-bi 117  df-dc 842  df-3or 1005  df-3an 1006  df-tru 1400  df-fal 1403  df-nf 1509  df-sb 1811  df-eu 2082  df-mo 2083  df-clab 2218  df-cleq 2224  df-clel 2227  df-nfc 2363  df-ne 2403  df-nel 2498  df-ral 2515  df-rex 2516  df-reu 2517  df-rab 2519  df-v 2804  df-sbc 3032  df-csb 3128  df-dif 3202  df-un 3204  df-in 3206  df-ss 3213  df-nul 3495  df-if 3606  df-pw 3654  df-sn 3675  df-pr 3676  df-op 3678  df-uni 3894  df-int 3929  df-iun 3972  df-br 4089  df-opab 4151  df-mpt 4152  df-tr 4188  df-id 4390  df-iord 4463  df-on 4465  df-ilim 4466  df-suc 4468  df-iom 4689  df-xp 4731  df-rel 4732  df-cnv 4733  df-co 4734  df-dm 4735  df-rn 4736  df-res 4737  df-ima 4738  df-iota 5286  df-fun 5328  df-fn 5329  df-f 5330  df-f1 5331  df-fo 5332  df-f1o 5333  df-fv 5334  df-riota 5971  df-ov 6021  df-oprab 6022  df-mpo 6023  df-1st 6303  df-2nd 6304  df-recs 6471  df-frec 6557  df-1o 6582  df-er 6702  df-en 6910  df-dom 6911  df-fin 6912  df-pnf 8216  df-mnf 8217  df-xr 8218  df-ltxr 8219  df-le 8220  df-sub 8352  df-neg 8353  df-reap 8755  df-ap 8762  df-inn 9144  df-n0 9403  df-z 9480  df-uz 9756  df-fz 10244  df-fzo 10378  df-ihash 11039  df-word 11118  df-lsw 11163  df-concat 11172  df-s1 11197  df-substr 11231  df-pfx 11258

This theorem is referenced by: (None)