| 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 |