Description: Lemma for general well-founded recursion. Two acceptable functions are compatible. (Contributed by Scott Fenton, 11-Sep-2023)
Ref | Expression | ||
---|---|---|---|
Hypotheses | frrlem15.1 | |
|
frrlem15.2 | |
||
Assertion | frrlem15 | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | frrlem15.1 | |
|
2 | frrlem15.2 | |
|
3 | vex | |
|
4 | vex | |
|
5 | 3 4 | breldm | |
6 | 5 | adantr | |
7 | vex | |
|
8 | 3 7 | breldm | |
9 | 8 | adantl | |
10 | 6 9 | elind | |
11 | id | |
|
12 | 4 | brresi | |
13 | 7 | brresi | |
14 | 12 13 | anbi12i | |
15 | an4 | |
|
16 | 14 15 | bitri | |
17 | 10 10 11 16 | syl21anbrc | |
18 | inss1 | |
|
19 | 1 | frrlem3 | |
20 | 18 19 | sstrid | |
21 | 20 | ad2antrl | |
22 | simpll | |
|
23 | frss | |
|
24 | 21 22 23 | sylc | |
25 | simplr | |
|
26 | sess2 | |
|
27 | 21 25 26 | sylc | |
28 | 1 | frrlem4 | |
29 | 28 | adantl | |
30 | 1 | frrlem4 | |
31 | incom | |
|
32 | 31 | reseq2i | |
33 | fneq12 | |
|
34 | 32 31 33 | mp2an | |
35 | 32 | fveq1i | |
36 | predeq2 | |
|
37 | 31 36 | ax-mp | |
38 | 32 37 | reseq12i | |
39 | 38 | oveq2i | |
40 | 35 39 | eqeq12i | |
41 | 31 40 | raleqbii | |
42 | 34 41 | anbi12i | |
43 | 30 42 | sylibr | |
44 | 43 | ancoms | |
45 | 44 | adantl | |
46 | frr3g | |
|
47 | 24 27 29 45 46 | syl211anc | |
48 | 47 | breqd | |
49 | 48 | biimprd | |
50 | 1 | frrlem2 | |
51 | 50 | funresd | |
52 | 51 | ad2antrl | |
53 | dffun2 | |
|
54 | 2sp | |
|
55 | 54 | sps | |
56 | 53 55 | simplbiim | |
57 | 52 56 | syl | |
58 | 49 57 | sylan2d | |
59 | 17 58 | syl5 | |