| Step | Hyp | Ref | Expression | 
						
							| 1 |  | efgval.w |  |-  W = ( _I ` Word ( I X. 2o ) ) | 
						
							| 2 |  | efgval.r |  |-  .~ = ( ~FG ` I ) | 
						
							| 3 |  | efgval2.m |  |-  M = ( y e. I , z e. 2o |-> <. y , ( 1o \ z ) >. ) | 
						
							| 4 |  | efgval2.t |  |-  T = ( v e. W |-> ( n e. ( 0 ... ( # ` v ) ) , w e. ( I X. 2o ) |-> ( v splice <. n , n , <" w ( M ` w ) "> >. ) ) ) | 
						
							| 5 |  | efgred.d |  |-  D = ( W \ U_ x e. W ran ( T ` x ) ) | 
						
							| 6 |  | efgred.s |  |-  S = ( m e. { t e. ( Word W \ { (/) } ) | ( ( t ` 0 ) e. D /\ A. k e. ( 1 ..^ ( # ` t ) ) ( t ` k ) e. ran ( T ` ( t ` ( k - 1 ) ) ) ) } |-> ( m ` ( ( # ` m ) - 1 ) ) ) | 
						
							| 7 |  | fveq1 |  |-  ( f = F -> ( f ` 0 ) = ( F ` 0 ) ) | 
						
							| 8 | 7 | eleq1d |  |-  ( f = F -> ( ( f ` 0 ) e. D <-> ( F ` 0 ) e. D ) ) | 
						
							| 9 |  | fveq2 |  |-  ( f = F -> ( # ` f ) = ( # ` F ) ) | 
						
							| 10 | 9 | oveq2d |  |-  ( f = F -> ( 1 ..^ ( # ` f ) ) = ( 1 ..^ ( # ` F ) ) ) | 
						
							| 11 |  | fveq1 |  |-  ( f = F -> ( f ` i ) = ( F ` i ) ) | 
						
							| 12 |  | fveq1 |  |-  ( f = F -> ( f ` ( i - 1 ) ) = ( F ` ( i - 1 ) ) ) | 
						
							| 13 | 12 | fveq2d |  |-  ( f = F -> ( T ` ( f ` ( i - 1 ) ) ) = ( T ` ( F ` ( i - 1 ) ) ) ) | 
						
							| 14 | 13 | rneqd |  |-  ( f = F -> ran ( T ` ( f ` ( i - 1 ) ) ) = ran ( T ` ( F ` ( i - 1 ) ) ) ) | 
						
							| 15 | 11 14 | eleq12d |  |-  ( f = F -> ( ( f ` i ) e. ran ( T ` ( f ` ( i - 1 ) ) ) <-> ( F ` i ) e. ran ( T ` ( F ` ( i - 1 ) ) ) ) ) | 
						
							| 16 | 10 15 | raleqbidv |  |-  ( f = F -> ( A. i e. ( 1 ..^ ( # ` f ) ) ( f ` i ) e. ran ( T ` ( f ` ( i - 1 ) ) ) <-> A. i e. ( 1 ..^ ( # ` F ) ) ( F ` i ) e. ran ( T ` ( F ` ( i - 1 ) ) ) ) ) | 
						
							| 17 | 8 16 | anbi12d |  |-  ( f = F -> ( ( ( f ` 0 ) e. D /\ A. i e. ( 1 ..^ ( # ` f ) ) ( f ` i ) e. ran ( T ` ( f ` ( i - 1 ) ) ) ) <-> ( ( F ` 0 ) e. D /\ A. i e. ( 1 ..^ ( # ` F ) ) ( F ` i ) e. ran ( T ` ( F ` ( i - 1 ) ) ) ) ) ) | 
						
							| 18 | 1 2 3 4 5 6 | efgsf |  |-  S : { t e. ( Word W \ { (/) } ) | ( ( t ` 0 ) e. D /\ A. k e. ( 1 ..^ ( # ` t ) ) ( t ` k ) e. ran ( T ` ( t ` ( k - 1 ) ) ) ) } --> W | 
						
							| 19 | 18 | fdmi |  |-  dom S = { t e. ( Word W \ { (/) } ) | ( ( t ` 0 ) e. D /\ A. k e. ( 1 ..^ ( # ` t ) ) ( t ` k ) e. ran ( T ` ( t ` ( k - 1 ) ) ) ) } | 
						
							| 20 |  | fveq1 |  |-  ( t = f -> ( t ` 0 ) = ( f ` 0 ) ) | 
						
							| 21 | 20 | eleq1d |  |-  ( t = f -> ( ( t ` 0 ) e. D <-> ( f ` 0 ) e. D ) ) | 
						
							| 22 |  | fveq2 |  |-  ( k = i -> ( t ` k ) = ( t ` i ) ) | 
						
							| 23 |  | fvoveq1 |  |-  ( k = i -> ( t ` ( k - 1 ) ) = ( t ` ( i - 1 ) ) ) | 
						
							| 24 | 23 | fveq2d |  |-  ( k = i -> ( T ` ( t ` ( k - 1 ) ) ) = ( T ` ( t ` ( i - 1 ) ) ) ) | 
						
							| 25 | 24 | rneqd |  |-  ( k = i -> ran ( T ` ( t ` ( k - 1 ) ) ) = ran ( T ` ( t ` ( i - 1 ) ) ) ) | 
						
							| 26 | 22 25 | eleq12d |  |-  ( k = i -> ( ( t ` k ) e. ran ( T ` ( t ` ( k - 1 ) ) ) <-> ( t ` i ) e. ran ( T ` ( t ` ( i - 1 ) ) ) ) ) | 
						
							| 27 | 26 | cbvralvw |  |-  ( A. k e. ( 1 ..^ ( # ` t ) ) ( t ` k ) e. ran ( T ` ( t ` ( k - 1 ) ) ) <-> A. i e. ( 1 ..^ ( # ` t ) ) ( t ` i ) e. ran ( T ` ( t ` ( i - 1 ) ) ) ) | 
						
							| 28 |  | fveq2 |  |-  ( t = f -> ( # ` t ) = ( # ` f ) ) | 
						
							| 29 | 28 | oveq2d |  |-  ( t = f -> ( 1 ..^ ( # ` t ) ) = ( 1 ..^ ( # ` f ) ) ) | 
						
							| 30 |  | fveq1 |  |-  ( t = f -> ( t ` i ) = ( f ` i ) ) | 
						
							| 31 |  | fveq1 |  |-  ( t = f -> ( t ` ( i - 1 ) ) = ( f ` ( i - 1 ) ) ) | 
						
							| 32 | 31 | fveq2d |  |-  ( t = f -> ( T ` ( t ` ( i - 1 ) ) ) = ( T ` ( f ` ( i - 1 ) ) ) ) | 
						
							| 33 | 32 | rneqd |  |-  ( t = f -> ran ( T ` ( t ` ( i - 1 ) ) ) = ran ( T ` ( f ` ( i - 1 ) ) ) ) | 
						
							| 34 | 30 33 | eleq12d |  |-  ( t = f -> ( ( t ` i ) e. ran ( T ` ( t ` ( i - 1 ) ) ) <-> ( f ` i ) e. ran ( T ` ( f ` ( i - 1 ) ) ) ) ) | 
						
							| 35 | 29 34 | raleqbidv |  |-  ( t = f -> ( A. i e. ( 1 ..^ ( # ` t ) ) ( t ` i ) e. ran ( T ` ( t ` ( i - 1 ) ) ) <-> A. i e. ( 1 ..^ ( # ` f ) ) ( f ` i ) e. ran ( T ` ( f ` ( i - 1 ) ) ) ) ) | 
						
							| 36 | 27 35 | bitrid |  |-  ( t = f -> ( A. k e. ( 1 ..^ ( # ` t ) ) ( t ` k ) e. ran ( T ` ( t ` ( k - 1 ) ) ) <-> A. i e. ( 1 ..^ ( # ` f ) ) ( f ` i ) e. ran ( T ` ( f ` ( i - 1 ) ) ) ) ) | 
						
							| 37 | 21 36 | anbi12d |  |-  ( t = f -> ( ( ( t ` 0 ) e. D /\ A. k e. ( 1 ..^ ( # ` t ) ) ( t ` k ) e. ran ( T ` ( t ` ( k - 1 ) ) ) ) <-> ( ( f ` 0 ) e. D /\ A. i e. ( 1 ..^ ( # ` f ) ) ( f ` i ) e. ran ( T ` ( f ` ( i - 1 ) ) ) ) ) ) | 
						
							| 38 | 37 | cbvrabv |  |-  { t e. ( Word W \ { (/) } ) | ( ( t ` 0 ) e. D /\ A. k e. ( 1 ..^ ( # ` t ) ) ( t ` k ) e. ran ( T ` ( t ` ( k - 1 ) ) ) ) } = { f e. ( Word W \ { (/) } ) | ( ( f ` 0 ) e. D /\ A. i e. ( 1 ..^ ( # ` f ) ) ( f ` i ) e. ran ( T ` ( f ` ( i - 1 ) ) ) ) } | 
						
							| 39 | 19 38 | eqtri |  |-  dom S = { f e. ( Word W \ { (/) } ) | ( ( f ` 0 ) e. D /\ A. i e. ( 1 ..^ ( # ` f ) ) ( f ` i ) e. ran ( T ` ( f ` ( i - 1 ) ) ) ) } | 
						
							| 40 | 17 39 | elrab2 |  |-  ( F e. dom S <-> ( F e. ( Word W \ { (/) } ) /\ ( ( F ` 0 ) e. D /\ A. i e. ( 1 ..^ ( # ` F ) ) ( F ` i ) e. ran ( T ` ( F ` ( i - 1 ) ) ) ) ) ) | 
						
							| 41 |  | 3anass |  |-  ( ( F e. ( Word W \ { (/) } ) /\ ( F ` 0 ) e. D /\ A. i e. ( 1 ..^ ( # ` F ) ) ( F ` i ) e. ran ( T ` ( F ` ( i - 1 ) ) ) ) <-> ( F e. ( Word W \ { (/) } ) /\ ( ( F ` 0 ) e. D /\ A. i e. ( 1 ..^ ( # ` F ) ) ( F ` i ) e. ran ( T ` ( F ` ( i - 1 ) ) ) ) ) ) | 
						
							| 42 | 40 41 | bitr4i |  |-  ( F e. dom S <-> ( F e. ( Word W \ { (/) } ) /\ ( F ` 0 ) e. D /\ A. i e. ( 1 ..^ ( # ` F ) ) ( F ` i ) e. ran ( T ` ( F ` ( i - 1 ) ) ) ) ) |