| 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 | 1 2 3 4 5 6 | efgsval |  |-  ( F e. dom S -> ( S ` F ) = ( F ` ( ( # ` F ) - 1 ) ) ) | 
						
							| 8 | 7 | adantr |  |-  ( ( F e. dom S /\ ( ( # ` F ) - 1 ) e. NN ) -> ( S ` F ) = ( F ` ( ( # ` F ) - 1 ) ) ) | 
						
							| 9 |  | fveq2 |  |-  ( i = ( ( # ` F ) - 1 ) -> ( F ` i ) = ( F ` ( ( # ` F ) - 1 ) ) ) | 
						
							| 10 |  | fvoveq1 |  |-  ( i = ( ( # ` F ) - 1 ) -> ( F ` ( i - 1 ) ) = ( F ` ( ( ( # ` F ) - 1 ) - 1 ) ) ) | 
						
							| 11 | 10 | fveq2d |  |-  ( i = ( ( # ` F ) - 1 ) -> ( T ` ( F ` ( i - 1 ) ) ) = ( T ` ( F ` ( ( ( # ` F ) - 1 ) - 1 ) ) ) ) | 
						
							| 12 | 11 | rneqd |  |-  ( i = ( ( # ` F ) - 1 ) -> ran ( T ` ( F ` ( i - 1 ) ) ) = ran ( T ` ( F ` ( ( ( # ` F ) - 1 ) - 1 ) ) ) ) | 
						
							| 13 | 9 12 | eleq12d |  |-  ( i = ( ( # ` F ) - 1 ) -> ( ( F ` i ) e. ran ( T ` ( F ` ( i - 1 ) ) ) <-> ( F ` ( ( # ` F ) - 1 ) ) e. ran ( T ` ( F ` ( ( ( # ` F ) - 1 ) - 1 ) ) ) ) ) | 
						
							| 14 | 1 2 3 4 5 6 | efgsdm |  |-  ( 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 ) ) ) ) ) | 
						
							| 15 | 14 | simp3bi |  |-  ( F e. dom S -> A. i e. ( 1 ..^ ( # ` F ) ) ( F ` i ) e. ran ( T ` ( F ` ( i - 1 ) ) ) ) | 
						
							| 16 | 15 | adantr |  |-  ( ( F e. dom S /\ ( ( # ` F ) - 1 ) e. NN ) -> A. i e. ( 1 ..^ ( # ` F ) ) ( F ` i ) e. ran ( T ` ( F ` ( i - 1 ) ) ) ) | 
						
							| 17 |  | simpr |  |-  ( ( F e. dom S /\ ( ( # ` F ) - 1 ) e. NN ) -> ( ( # ` F ) - 1 ) e. NN ) | 
						
							| 18 |  | nnuz |  |-  NN = ( ZZ>= ` 1 ) | 
						
							| 19 | 17 18 | eleqtrdi |  |-  ( ( F e. dom S /\ ( ( # ` F ) - 1 ) e. NN ) -> ( ( # ` F ) - 1 ) e. ( ZZ>= ` 1 ) ) | 
						
							| 20 |  | eluzfz1 |  |-  ( ( ( # ` F ) - 1 ) e. ( ZZ>= ` 1 ) -> 1 e. ( 1 ... ( ( # ` F ) - 1 ) ) ) | 
						
							| 21 | 19 20 | syl |  |-  ( ( F e. dom S /\ ( ( # ` F ) - 1 ) e. NN ) -> 1 e. ( 1 ... ( ( # ` F ) - 1 ) ) ) | 
						
							| 22 | 14 | simp1bi |  |-  ( F e. dom S -> F e. ( Word W \ { (/) } ) ) | 
						
							| 23 | 22 | adantr |  |-  ( ( F e. dom S /\ ( ( # ` F ) - 1 ) e. NN ) -> F e. ( Word W \ { (/) } ) ) | 
						
							| 24 | 23 | eldifad |  |-  ( ( F e. dom S /\ ( ( # ` F ) - 1 ) e. NN ) -> F e. Word W ) | 
						
							| 25 |  | lencl |  |-  ( F e. Word W -> ( # ` F ) e. NN0 ) | 
						
							| 26 |  | nn0z |  |-  ( ( # ` F ) e. NN0 -> ( # ` F ) e. ZZ ) | 
						
							| 27 |  | fzoval |  |-  ( ( # ` F ) e. ZZ -> ( 1 ..^ ( # ` F ) ) = ( 1 ... ( ( # ` F ) - 1 ) ) ) | 
						
							| 28 | 24 25 26 27 | 4syl |  |-  ( ( F e. dom S /\ ( ( # ` F ) - 1 ) e. NN ) -> ( 1 ..^ ( # ` F ) ) = ( 1 ... ( ( # ` F ) - 1 ) ) ) | 
						
							| 29 | 21 28 | eleqtrrd |  |-  ( ( F e. dom S /\ ( ( # ` F ) - 1 ) e. NN ) -> 1 e. ( 1 ..^ ( # ` F ) ) ) | 
						
							| 30 |  | fzoend |  |-  ( 1 e. ( 1 ..^ ( # ` F ) ) -> ( ( # ` F ) - 1 ) e. ( 1 ..^ ( # ` F ) ) ) | 
						
							| 31 | 29 30 | syl |  |-  ( ( F e. dom S /\ ( ( # ` F ) - 1 ) e. NN ) -> ( ( # ` F ) - 1 ) e. ( 1 ..^ ( # ` F ) ) ) | 
						
							| 32 | 13 16 31 | rspcdva |  |-  ( ( F e. dom S /\ ( ( # ` F ) - 1 ) e. NN ) -> ( F ` ( ( # ` F ) - 1 ) ) e. ran ( T ` ( F ` ( ( ( # ` F ) - 1 ) - 1 ) ) ) ) | 
						
							| 33 | 8 32 | eqeltrd |  |-  ( ( F e. dom S /\ ( ( # ` F ) - 1 ) e. NN ) -> ( S ` F ) e. ran ( T ` ( F ` ( ( ( # ` F ) - 1 ) - 1 ) ) ) ) |