| 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 |  | id |  |-  ( m = t -> m = t ) | 
						
							| 8 |  | fveq2 |  |-  ( m = t -> ( # ` m ) = ( # ` t ) ) | 
						
							| 9 | 8 | oveq1d |  |-  ( m = t -> ( ( # ` m ) - 1 ) = ( ( # ` t ) - 1 ) ) | 
						
							| 10 | 7 9 | fveq12d |  |-  ( m = t -> ( m ` ( ( # ` m ) - 1 ) ) = ( t ` ( ( # ` t ) - 1 ) ) ) | 
						
							| 11 | 10 | eleq1d |  |-  ( m = t -> ( ( m ` ( ( # ` m ) - 1 ) ) e. W <-> ( t ` ( ( # ` t ) - 1 ) ) e. W ) ) | 
						
							| 12 | 11 | ralrab2 |  |-  ( A. 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 ) ) e. W <-> A. t e. ( Word W \ { (/) } ) ( ( ( t ` 0 ) e. D /\ A. k e. ( 1 ..^ ( # ` t ) ) ( t ` k ) e. ran ( T ` ( t ` ( k - 1 ) ) ) ) -> ( t ` ( ( # ` t ) - 1 ) ) e. W ) ) | 
						
							| 13 |  | eldifi |  |-  ( t e. ( Word W \ { (/) } ) -> t e. Word W ) | 
						
							| 14 |  | wrdf |  |-  ( t e. Word W -> t : ( 0 ..^ ( # ` t ) ) --> W ) | 
						
							| 15 | 13 14 | syl |  |-  ( t e. ( Word W \ { (/) } ) -> t : ( 0 ..^ ( # ` t ) ) --> W ) | 
						
							| 16 |  | eldifsn |  |-  ( t e. ( Word W \ { (/) } ) <-> ( t e. Word W /\ t =/= (/) ) ) | 
						
							| 17 |  | lennncl |  |-  ( ( t e. Word W /\ t =/= (/) ) -> ( # ` t ) e. NN ) | 
						
							| 18 | 16 17 | sylbi |  |-  ( t e. ( Word W \ { (/) } ) -> ( # ` t ) e. NN ) | 
						
							| 19 |  | fzo0end |  |-  ( ( # ` t ) e. NN -> ( ( # ` t ) - 1 ) e. ( 0 ..^ ( # ` t ) ) ) | 
						
							| 20 | 18 19 | syl |  |-  ( t e. ( Word W \ { (/) } ) -> ( ( # ` t ) - 1 ) e. ( 0 ..^ ( # ` t ) ) ) | 
						
							| 21 | 15 20 | ffvelcdmd |  |-  ( t e. ( Word W \ { (/) } ) -> ( t ` ( ( # ` t ) - 1 ) ) e. W ) | 
						
							| 22 | 21 | a1d |  |-  ( t e. ( Word W \ { (/) } ) -> ( ( ( t ` 0 ) e. D /\ A. k e. ( 1 ..^ ( # ` t ) ) ( t ` k ) e. ran ( T ` ( t ` ( k - 1 ) ) ) ) -> ( t ` ( ( # ` t ) - 1 ) ) e. W ) ) | 
						
							| 23 | 12 22 | mprgbir |  |-  A. 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 ) ) e. W | 
						
							| 24 | 6 | fmpt |  |-  ( A. 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 ) ) e. W <-> S : { t e. ( Word W \ { (/) } ) | ( ( t ` 0 ) e. D /\ A. k e. ( 1 ..^ ( # ` t ) ) ( t ` k ) e. ran ( T ` ( t ` ( k - 1 ) ) ) ) } --> W ) | 
						
							| 25 | 23 24 | mpbi |  |-  S : { t e. ( Word W \ { (/) } ) | ( ( t ` 0 ) e. D /\ A. k e. ( 1 ..^ ( # ` t ) ) ( t ` k ) e. ran ( T ` ( t ` ( k - 1 ) ) ) ) } --> W |