| Step |
Hyp |
Ref |
Expression |
| 1 |
|
soxp.1 |
|- T = { <. x , y >. | ( ( x e. ( A X. B ) /\ y e. ( A X. B ) ) /\ ( ( 1st ` x ) R ( 1st ` y ) \/ ( ( 1st ` x ) = ( 1st ` y ) /\ ( 2nd ` x ) S ( 2nd ` y ) ) ) ) } |
| 2 |
|
sopo |
|- ( R Or A -> R Po A ) |
| 3 |
|
sopo |
|- ( S Or B -> S Po B ) |
| 4 |
1
|
poxp |
|- ( ( R Po A /\ S Po B ) -> T Po ( A X. B ) ) |
| 5 |
2 3 4
|
syl2an |
|- ( ( R Or A /\ S Or B ) -> T Po ( A X. B ) ) |
| 6 |
|
elxp |
|- ( t e. ( A X. B ) <-> E. a E. b ( t = <. a , b >. /\ ( a e. A /\ b e. B ) ) ) |
| 7 |
|
elxp |
|- ( u e. ( A X. B ) <-> E. c E. d ( u = <. c , d >. /\ ( c e. A /\ d e. B ) ) ) |
| 8 |
|
ioran |
|- ( -. ( ( a R c \/ ( a = c /\ b S d ) ) \/ ( a = c /\ b = d ) ) <-> ( -. ( a R c \/ ( a = c /\ b S d ) ) /\ -. ( a = c /\ b = d ) ) ) |
| 9 |
|
ioran |
|- ( -. ( a R c \/ ( a = c /\ b S d ) ) <-> ( -. a R c /\ -. ( a = c /\ b S d ) ) ) |
| 10 |
|
ianor |
|- ( -. ( a = c /\ b S d ) <-> ( -. a = c \/ -. b S d ) ) |
| 11 |
10
|
anbi2i |
|- ( ( -. a R c /\ -. ( a = c /\ b S d ) ) <-> ( -. a R c /\ ( -. a = c \/ -. b S d ) ) ) |
| 12 |
9 11
|
bitri |
|- ( -. ( a R c \/ ( a = c /\ b S d ) ) <-> ( -. a R c /\ ( -. a = c \/ -. b S d ) ) ) |
| 13 |
|
ianor |
|- ( -. ( a = c /\ b = d ) <-> ( -. a = c \/ -. b = d ) ) |
| 14 |
12 13
|
anbi12i |
|- ( ( -. ( a R c \/ ( a = c /\ b S d ) ) /\ -. ( a = c /\ b = d ) ) <-> ( ( -. a R c /\ ( -. a = c \/ -. b S d ) ) /\ ( -. a = c \/ -. b = d ) ) ) |
| 15 |
8 14
|
bitri |
|- ( -. ( ( a R c \/ ( a = c /\ b S d ) ) \/ ( a = c /\ b = d ) ) <-> ( ( -. a R c /\ ( -. a = c \/ -. b S d ) ) /\ ( -. a = c \/ -. b = d ) ) ) |
| 16 |
|
solin |
|- ( ( R Or A /\ ( a e. A /\ c e. A ) ) -> ( a R c \/ a = c \/ c R a ) ) |
| 17 |
|
3orass |
|- ( ( a R c \/ a = c \/ c R a ) <-> ( a R c \/ ( a = c \/ c R a ) ) ) |
| 18 |
|
df-or |
|- ( ( a R c \/ ( a = c \/ c R a ) ) <-> ( -. a R c -> ( a = c \/ c R a ) ) ) |
| 19 |
17 18
|
bitri |
|- ( ( a R c \/ a = c \/ c R a ) <-> ( -. a R c -> ( a = c \/ c R a ) ) ) |
| 20 |
16 19
|
sylib |
|- ( ( R Or A /\ ( a e. A /\ c e. A ) ) -> ( -. a R c -> ( a = c \/ c R a ) ) ) |
| 21 |
|
solin |
|- ( ( S Or B /\ ( b e. B /\ d e. B ) ) -> ( b S d \/ b = d \/ d S b ) ) |
| 22 |
|
3orass |
|- ( ( b S d \/ b = d \/ d S b ) <-> ( b S d \/ ( b = d \/ d S b ) ) ) |
| 23 |
|
df-or |
|- ( ( b S d \/ ( b = d \/ d S b ) ) <-> ( -. b S d -> ( b = d \/ d S b ) ) ) |
| 24 |
22 23
|
bitri |
|- ( ( b S d \/ b = d \/ d S b ) <-> ( -. b S d -> ( b = d \/ d S b ) ) ) |
| 25 |
21 24
|
sylib |
|- ( ( S Or B /\ ( b e. B /\ d e. B ) ) -> ( -. b S d -> ( b = d \/ d S b ) ) ) |
| 26 |
25
|
orim2d |
|- ( ( S Or B /\ ( b e. B /\ d e. B ) ) -> ( ( -. a = c \/ -. b S d ) -> ( -. a = c \/ ( b = d \/ d S b ) ) ) ) |
| 27 |
20 26
|
im2anan9 |
|- ( ( ( R Or A /\ ( a e. A /\ c e. A ) ) /\ ( S Or B /\ ( b e. B /\ d e. B ) ) ) -> ( ( -. a R c /\ ( -. a = c \/ -. b S d ) ) -> ( ( a = c \/ c R a ) /\ ( -. a = c \/ ( b = d \/ d S b ) ) ) ) ) |
| 28 |
|
pm2.53 |
|- ( ( a = c \/ c R a ) -> ( -. a = c -> c R a ) ) |
| 29 |
|
orc |
|- ( c R a -> ( c R a \/ ( c = a /\ d S b ) ) ) |
| 30 |
28 29
|
syl6 |
|- ( ( a = c \/ c R a ) -> ( -. a = c -> ( c R a \/ ( c = a /\ d S b ) ) ) ) |
| 31 |
30
|
adantr |
|- ( ( ( a = c \/ c R a ) /\ ( -. a = c \/ ( b = d \/ d S b ) ) ) -> ( -. a = c -> ( c R a \/ ( c = a /\ d S b ) ) ) ) |
| 32 |
|
orel1 |
|- ( -. b = d -> ( ( b = d \/ d S b ) -> d S b ) ) |
| 33 |
32
|
orim2d |
|- ( -. b = d -> ( ( -. a = c \/ ( b = d \/ d S b ) ) -> ( -. a = c \/ d S b ) ) ) |
| 34 |
33
|
anim2d |
|- ( -. b = d -> ( ( ( a = c \/ c R a ) /\ ( -. a = c \/ ( b = d \/ d S b ) ) ) -> ( ( a = c \/ c R a ) /\ ( -. a = c \/ d S b ) ) ) ) |
| 35 |
|
imor |
|- ( ( a = c -> d S b ) <-> ( -. a = c \/ d S b ) ) |
| 36 |
35
|
biimpri |
|- ( ( -. a = c \/ d S b ) -> ( a = c -> d S b ) ) |
| 37 |
36
|
com12 |
|- ( a = c -> ( ( -. a = c \/ d S b ) -> d S b ) ) |
| 38 |
|
equcomi |
|- ( a = c -> c = a ) |
| 39 |
38
|
anim1i |
|- ( ( a = c /\ d S b ) -> ( c = a /\ d S b ) ) |
| 40 |
39
|
olcd |
|- ( ( a = c /\ d S b ) -> ( c R a \/ ( c = a /\ d S b ) ) ) |
| 41 |
40
|
ex |
|- ( a = c -> ( d S b -> ( c R a \/ ( c = a /\ d S b ) ) ) ) |
| 42 |
37 41
|
syld |
|- ( a = c -> ( ( -. a = c \/ d S b ) -> ( c R a \/ ( c = a /\ d S b ) ) ) ) |
| 43 |
29
|
a1d |
|- ( c R a -> ( ( -. a = c \/ d S b ) -> ( c R a \/ ( c = a /\ d S b ) ) ) ) |
| 44 |
42 43
|
jaoi |
|- ( ( a = c \/ c R a ) -> ( ( -. a = c \/ d S b ) -> ( c R a \/ ( c = a /\ d S b ) ) ) ) |
| 45 |
44
|
imp |
|- ( ( ( a = c \/ c R a ) /\ ( -. a = c \/ d S b ) ) -> ( c R a \/ ( c = a /\ d S b ) ) ) |
| 46 |
34 45
|
syl6com |
|- ( ( ( a = c \/ c R a ) /\ ( -. a = c \/ ( b = d \/ d S b ) ) ) -> ( -. b = d -> ( c R a \/ ( c = a /\ d S b ) ) ) ) |
| 47 |
31 46
|
jaod |
|- ( ( ( a = c \/ c R a ) /\ ( -. a = c \/ ( b = d \/ d S b ) ) ) -> ( ( -. a = c \/ -. b = d ) -> ( c R a \/ ( c = a /\ d S b ) ) ) ) |
| 48 |
27 47
|
syl6 |
|- ( ( ( R Or A /\ ( a e. A /\ c e. A ) ) /\ ( S Or B /\ ( b e. B /\ d e. B ) ) ) -> ( ( -. a R c /\ ( -. a = c \/ -. b S d ) ) -> ( ( -. a = c \/ -. b = d ) -> ( c R a \/ ( c = a /\ d S b ) ) ) ) ) |
| 49 |
48
|
impd |
|- ( ( ( R Or A /\ ( a e. A /\ c e. A ) ) /\ ( S Or B /\ ( b e. B /\ d e. B ) ) ) -> ( ( ( -. a R c /\ ( -. a = c \/ -. b S d ) ) /\ ( -. a = c \/ -. b = d ) ) -> ( c R a \/ ( c = a /\ d S b ) ) ) ) |
| 50 |
15 49
|
biimtrid |
|- ( ( ( R Or A /\ ( a e. A /\ c e. A ) ) /\ ( S Or B /\ ( b e. B /\ d e. B ) ) ) -> ( -. ( ( a R c \/ ( a = c /\ b S d ) ) \/ ( a = c /\ b = d ) ) -> ( c R a \/ ( c = a /\ d S b ) ) ) ) |
| 51 |
|
df-3or |
|- ( ( ( a R c \/ ( a = c /\ b S d ) ) \/ ( a = c /\ b = d ) \/ ( c R a \/ ( c = a /\ d S b ) ) ) <-> ( ( ( a R c \/ ( a = c /\ b S d ) ) \/ ( a = c /\ b = d ) ) \/ ( c R a \/ ( c = a /\ d S b ) ) ) ) |
| 52 |
|
df-or |
|- ( ( ( ( a R c \/ ( a = c /\ b S d ) ) \/ ( a = c /\ b = d ) ) \/ ( c R a \/ ( c = a /\ d S b ) ) ) <-> ( -. ( ( a R c \/ ( a = c /\ b S d ) ) \/ ( a = c /\ b = d ) ) -> ( c R a \/ ( c = a /\ d S b ) ) ) ) |
| 53 |
51 52
|
bitri |
|- ( ( ( a R c \/ ( a = c /\ b S d ) ) \/ ( a = c /\ b = d ) \/ ( c R a \/ ( c = a /\ d S b ) ) ) <-> ( -. ( ( a R c \/ ( a = c /\ b S d ) ) \/ ( a = c /\ b = d ) ) -> ( c R a \/ ( c = a /\ d S b ) ) ) ) |
| 54 |
50 53
|
sylibr |
|- ( ( ( R Or A /\ ( a e. A /\ c e. A ) ) /\ ( S Or B /\ ( b e. B /\ d e. B ) ) ) -> ( ( a R c \/ ( a = c /\ b S d ) ) \/ ( a = c /\ b = d ) \/ ( c R a \/ ( c = a /\ d S b ) ) ) ) |
| 55 |
|
pm3.2 |
|- ( ( ( a e. A /\ c e. A ) /\ ( b e. B /\ d e. B ) ) -> ( ( a R c \/ ( a = c /\ b S d ) ) -> ( ( ( a e. A /\ c e. A ) /\ ( b e. B /\ d e. B ) ) /\ ( a R c \/ ( a = c /\ b S d ) ) ) ) ) |
| 56 |
55
|
ad2ant2l |
|- ( ( ( R Or A /\ ( a e. A /\ c e. A ) ) /\ ( S Or B /\ ( b e. B /\ d e. B ) ) ) -> ( ( a R c \/ ( a = c /\ b S d ) ) -> ( ( ( a e. A /\ c e. A ) /\ ( b e. B /\ d e. B ) ) /\ ( a R c \/ ( a = c /\ b S d ) ) ) ) ) |
| 57 |
|
idd |
|- ( ( ( R Or A /\ ( a e. A /\ c e. A ) ) /\ ( S Or B /\ ( b e. B /\ d e. B ) ) ) -> ( ( a = c /\ b = d ) -> ( a = c /\ b = d ) ) ) |
| 58 |
|
simpr |
|- ( ( R Or A /\ ( a e. A /\ c e. A ) ) -> ( a e. A /\ c e. A ) ) |
| 59 |
58
|
ancomd |
|- ( ( R Or A /\ ( a e. A /\ c e. A ) ) -> ( c e. A /\ a e. A ) ) |
| 60 |
|
simpr |
|- ( ( S Or B /\ ( b e. B /\ d e. B ) ) -> ( b e. B /\ d e. B ) ) |
| 61 |
60
|
ancomd |
|- ( ( S Or B /\ ( b e. B /\ d e. B ) ) -> ( d e. B /\ b e. B ) ) |
| 62 |
|
pm3.2 |
|- ( ( ( c e. A /\ a e. A ) /\ ( d e. B /\ b e. B ) ) -> ( ( c R a \/ ( c = a /\ d S b ) ) -> ( ( ( c e. A /\ a e. A ) /\ ( d e. B /\ b e. B ) ) /\ ( c R a \/ ( c = a /\ d S b ) ) ) ) ) |
| 63 |
59 61 62
|
syl2an |
|- ( ( ( R Or A /\ ( a e. A /\ c e. A ) ) /\ ( S Or B /\ ( b e. B /\ d e. B ) ) ) -> ( ( c R a \/ ( c = a /\ d S b ) ) -> ( ( ( c e. A /\ a e. A ) /\ ( d e. B /\ b e. B ) ) /\ ( c R a \/ ( c = a /\ d S b ) ) ) ) ) |
| 64 |
56 57 63
|
3orim123d |
|- ( ( ( R Or A /\ ( a e. A /\ c e. A ) ) /\ ( S Or B /\ ( b e. B /\ d e. B ) ) ) -> ( ( ( a R c \/ ( a = c /\ b S d ) ) \/ ( a = c /\ b = d ) \/ ( c R a \/ ( c = a /\ d S b ) ) ) -> ( ( ( ( a e. A /\ c e. A ) /\ ( b e. B /\ d e. B ) ) /\ ( a R c \/ ( a = c /\ b S d ) ) ) \/ ( a = c /\ b = d ) \/ ( ( ( c e. A /\ a e. A ) /\ ( d e. B /\ b e. B ) ) /\ ( c R a \/ ( c = a /\ d S b ) ) ) ) ) ) |
| 65 |
54 64
|
mpd |
|- ( ( ( R Or A /\ ( a e. A /\ c e. A ) ) /\ ( S Or B /\ ( b e. B /\ d e. B ) ) ) -> ( ( ( ( a e. A /\ c e. A ) /\ ( b e. B /\ d e. B ) ) /\ ( a R c \/ ( a = c /\ b S d ) ) ) \/ ( a = c /\ b = d ) \/ ( ( ( c e. A /\ a e. A ) /\ ( d e. B /\ b e. B ) ) /\ ( c R a \/ ( c = a /\ d S b ) ) ) ) ) |
| 66 |
65
|
an4s |
|- ( ( ( R Or A /\ S Or B ) /\ ( ( a e. A /\ c e. A ) /\ ( b e. B /\ d e. B ) ) ) -> ( ( ( ( a e. A /\ c e. A ) /\ ( b e. B /\ d e. B ) ) /\ ( a R c \/ ( a = c /\ b S d ) ) ) \/ ( a = c /\ b = d ) \/ ( ( ( c e. A /\ a e. A ) /\ ( d e. B /\ b e. B ) ) /\ ( c R a \/ ( c = a /\ d S b ) ) ) ) ) |
| 67 |
66
|
expcom |
|- ( ( ( a e. A /\ c e. A ) /\ ( b e. B /\ d e. B ) ) -> ( ( R Or A /\ S Or B ) -> ( ( ( ( a e. A /\ c e. A ) /\ ( b e. B /\ d e. B ) ) /\ ( a R c \/ ( a = c /\ b S d ) ) ) \/ ( a = c /\ b = d ) \/ ( ( ( c e. A /\ a e. A ) /\ ( d e. B /\ b e. B ) ) /\ ( c R a \/ ( c = a /\ d S b ) ) ) ) ) ) |
| 68 |
67
|
an4s |
|- ( ( ( a e. A /\ b e. B ) /\ ( c e. A /\ d e. B ) ) -> ( ( R Or A /\ S Or B ) -> ( ( ( ( a e. A /\ c e. A ) /\ ( b e. B /\ d e. B ) ) /\ ( a R c \/ ( a = c /\ b S d ) ) ) \/ ( a = c /\ b = d ) \/ ( ( ( c e. A /\ a e. A ) /\ ( d e. B /\ b e. B ) ) /\ ( c R a \/ ( c = a /\ d S b ) ) ) ) ) ) |
| 69 |
|
breq12 |
|- ( ( t = <. a , b >. /\ u = <. c , d >. ) -> ( t T u <-> <. a , b >. T <. c , d >. ) ) |
| 70 |
|
eqeq12 |
|- ( ( t = <. a , b >. /\ u = <. c , d >. ) -> ( t = u <-> <. a , b >. = <. c , d >. ) ) |
| 71 |
|
breq12 |
|- ( ( u = <. c , d >. /\ t = <. a , b >. ) -> ( u T t <-> <. c , d >. T <. a , b >. ) ) |
| 72 |
71
|
ancoms |
|- ( ( t = <. a , b >. /\ u = <. c , d >. ) -> ( u T t <-> <. c , d >. T <. a , b >. ) ) |
| 73 |
69 70 72
|
3orbi123d |
|- ( ( t = <. a , b >. /\ u = <. c , d >. ) -> ( ( t T u \/ t = u \/ u T t ) <-> ( <. a , b >. T <. c , d >. \/ <. a , b >. = <. c , d >. \/ <. c , d >. T <. a , b >. ) ) ) |
| 74 |
1
|
xporderlem |
|- ( <. a , b >. T <. c , d >. <-> ( ( ( a e. A /\ c e. A ) /\ ( b e. B /\ d e. B ) ) /\ ( a R c \/ ( a = c /\ b S d ) ) ) ) |
| 75 |
|
vex |
|- a e. _V |
| 76 |
|
vex |
|- b e. _V |
| 77 |
75 76
|
opth |
|- ( <. a , b >. = <. c , d >. <-> ( a = c /\ b = d ) ) |
| 78 |
1
|
xporderlem |
|- ( <. c , d >. T <. a , b >. <-> ( ( ( c e. A /\ a e. A ) /\ ( d e. B /\ b e. B ) ) /\ ( c R a \/ ( c = a /\ d S b ) ) ) ) |
| 79 |
74 77 78
|
3orbi123i |
|- ( ( <. a , b >. T <. c , d >. \/ <. a , b >. = <. c , d >. \/ <. c , d >. T <. a , b >. ) <-> ( ( ( ( a e. A /\ c e. A ) /\ ( b e. B /\ d e. B ) ) /\ ( a R c \/ ( a = c /\ b S d ) ) ) \/ ( a = c /\ b = d ) \/ ( ( ( c e. A /\ a e. A ) /\ ( d e. B /\ b e. B ) ) /\ ( c R a \/ ( c = a /\ d S b ) ) ) ) ) |
| 80 |
73 79
|
bitrdi |
|- ( ( t = <. a , b >. /\ u = <. c , d >. ) -> ( ( t T u \/ t = u \/ u T t ) <-> ( ( ( ( a e. A /\ c e. A ) /\ ( b e. B /\ d e. B ) ) /\ ( a R c \/ ( a = c /\ b S d ) ) ) \/ ( a = c /\ b = d ) \/ ( ( ( c e. A /\ a e. A ) /\ ( d e. B /\ b e. B ) ) /\ ( c R a \/ ( c = a /\ d S b ) ) ) ) ) ) |
| 81 |
80
|
biimprcd |
|- ( ( ( ( ( a e. A /\ c e. A ) /\ ( b e. B /\ d e. B ) ) /\ ( a R c \/ ( a = c /\ b S d ) ) ) \/ ( a = c /\ b = d ) \/ ( ( ( c e. A /\ a e. A ) /\ ( d e. B /\ b e. B ) ) /\ ( c R a \/ ( c = a /\ d S b ) ) ) ) -> ( ( t = <. a , b >. /\ u = <. c , d >. ) -> ( t T u \/ t = u \/ u T t ) ) ) |
| 82 |
68 81
|
syl6 |
|- ( ( ( a e. A /\ b e. B ) /\ ( c e. A /\ d e. B ) ) -> ( ( R Or A /\ S Or B ) -> ( ( t = <. a , b >. /\ u = <. c , d >. ) -> ( t T u \/ t = u \/ u T t ) ) ) ) |
| 83 |
82
|
com3r |
|- ( ( t = <. a , b >. /\ u = <. c , d >. ) -> ( ( ( a e. A /\ b e. B ) /\ ( c e. A /\ d e. B ) ) -> ( ( R Or A /\ S Or B ) -> ( t T u \/ t = u \/ u T t ) ) ) ) |
| 84 |
83
|
imp |
|- ( ( ( t = <. a , b >. /\ u = <. c , d >. ) /\ ( ( a e. A /\ b e. B ) /\ ( c e. A /\ d e. B ) ) ) -> ( ( R Or A /\ S Or B ) -> ( t T u \/ t = u \/ u T t ) ) ) |
| 85 |
84
|
an4s |
|- ( ( ( t = <. a , b >. /\ ( a e. A /\ b e. B ) ) /\ ( u = <. c , d >. /\ ( c e. A /\ d e. B ) ) ) -> ( ( R Or A /\ S Or B ) -> ( t T u \/ t = u \/ u T t ) ) ) |
| 86 |
85
|
expcom |
|- ( ( u = <. c , d >. /\ ( c e. A /\ d e. B ) ) -> ( ( t = <. a , b >. /\ ( a e. A /\ b e. B ) ) -> ( ( R Or A /\ S Or B ) -> ( t T u \/ t = u \/ u T t ) ) ) ) |
| 87 |
86
|
exlimivv |
|- ( E. c E. d ( u = <. c , d >. /\ ( c e. A /\ d e. B ) ) -> ( ( t = <. a , b >. /\ ( a e. A /\ b e. B ) ) -> ( ( R Or A /\ S Or B ) -> ( t T u \/ t = u \/ u T t ) ) ) ) |
| 88 |
87
|
com12 |
|- ( ( t = <. a , b >. /\ ( a e. A /\ b e. B ) ) -> ( E. c E. d ( u = <. c , d >. /\ ( c e. A /\ d e. B ) ) -> ( ( R Or A /\ S Or B ) -> ( t T u \/ t = u \/ u T t ) ) ) ) |
| 89 |
88
|
exlimivv |
|- ( E. a E. b ( t = <. a , b >. /\ ( a e. A /\ b e. B ) ) -> ( E. c E. d ( u = <. c , d >. /\ ( c e. A /\ d e. B ) ) -> ( ( R Or A /\ S Or B ) -> ( t T u \/ t = u \/ u T t ) ) ) ) |
| 90 |
89
|
imp |
|- ( ( E. a E. b ( t = <. a , b >. /\ ( a e. A /\ b e. B ) ) /\ E. c E. d ( u = <. c , d >. /\ ( c e. A /\ d e. B ) ) ) -> ( ( R Or A /\ S Or B ) -> ( t T u \/ t = u \/ u T t ) ) ) |
| 91 |
6 7 90
|
syl2anb |
|- ( ( t e. ( A X. B ) /\ u e. ( A X. B ) ) -> ( ( R Or A /\ S Or B ) -> ( t T u \/ t = u \/ u T t ) ) ) |
| 92 |
91
|
com12 |
|- ( ( R Or A /\ S Or B ) -> ( ( t e. ( A X. B ) /\ u e. ( A X. B ) ) -> ( t T u \/ t = u \/ u T t ) ) ) |
| 93 |
92
|
ralrimivv |
|- ( ( R Or A /\ S Or B ) -> A. t e. ( A X. B ) A. u e. ( A X. B ) ( t T u \/ t = u \/ u T t ) ) |
| 94 |
|
df-so |
|- ( T Or ( A X. B ) <-> ( T Po ( A X. B ) /\ A. t e. ( A X. B ) A. u e. ( A X. B ) ( t T u \/ t = u \/ u T t ) ) ) |
| 95 |
5 93 94
|
sylanbrc |
|- ( ( R Or A /\ S Or B ) -> T Or ( A X. B ) ) |