| Step | Hyp | Ref | Expression | 
						
							| 1 |  | spllen.s |  |-  ( ph -> S e. Word A ) | 
						
							| 2 |  | spllen.f |  |-  ( ph -> F e. ( 0 ... T ) ) | 
						
							| 3 |  | spllen.t |  |-  ( ph -> T e. ( 0 ... ( # ` S ) ) ) | 
						
							| 4 |  | spllen.r |  |-  ( ph -> R e. Word A ) | 
						
							| 5 |  | splfv2a.x |  |-  ( ph -> X e. ( 0 ..^ ( # ` R ) ) ) | 
						
							| 6 |  | splval |  |-  ( ( S e. Word A /\ ( F e. ( 0 ... T ) /\ T e. ( 0 ... ( # ` S ) ) /\ R e. Word A ) ) -> ( S splice <. F , T , R >. ) = ( ( ( S prefix F ) ++ R ) ++ ( S substr <. T , ( # ` S ) >. ) ) ) | 
						
							| 7 | 1 2 3 4 6 | syl13anc |  |-  ( ph -> ( S splice <. F , T , R >. ) = ( ( ( S prefix F ) ++ R ) ++ ( S substr <. T , ( # ` S ) >. ) ) ) | 
						
							| 8 |  | elfznn0 |  |-  ( F e. ( 0 ... T ) -> F e. NN0 ) | 
						
							| 9 | 2 8 | syl |  |-  ( ph -> F e. NN0 ) | 
						
							| 10 | 9 | nn0cnd |  |-  ( ph -> F e. CC ) | 
						
							| 11 |  | elfzonn0 |  |-  ( X e. ( 0 ..^ ( # ` R ) ) -> X e. NN0 ) | 
						
							| 12 | 5 11 | syl |  |-  ( ph -> X e. NN0 ) | 
						
							| 13 | 12 | nn0cnd |  |-  ( ph -> X e. CC ) | 
						
							| 14 | 10 13 | addcomd |  |-  ( ph -> ( F + X ) = ( X + F ) ) | 
						
							| 15 |  | nn0uz |  |-  NN0 = ( ZZ>= ` 0 ) | 
						
							| 16 | 9 15 | eleqtrdi |  |-  ( ph -> F e. ( ZZ>= ` 0 ) ) | 
						
							| 17 |  | elfzuz3 |  |-  ( T e. ( 0 ... ( # ` S ) ) -> ( # ` S ) e. ( ZZ>= ` T ) ) | 
						
							| 18 | 3 17 | syl |  |-  ( ph -> ( # ` S ) e. ( ZZ>= ` T ) ) | 
						
							| 19 |  | elfzuz3 |  |-  ( F e. ( 0 ... T ) -> T e. ( ZZ>= ` F ) ) | 
						
							| 20 | 2 19 | syl |  |-  ( ph -> T e. ( ZZ>= ` F ) ) | 
						
							| 21 |  | uztrn |  |-  ( ( ( # ` S ) e. ( ZZ>= ` T ) /\ T e. ( ZZ>= ` F ) ) -> ( # ` S ) e. ( ZZ>= ` F ) ) | 
						
							| 22 | 18 20 21 | syl2anc |  |-  ( ph -> ( # ` S ) e. ( ZZ>= ` F ) ) | 
						
							| 23 |  | elfzuzb |  |-  ( F e. ( 0 ... ( # ` S ) ) <-> ( F e. ( ZZ>= ` 0 ) /\ ( # ` S ) e. ( ZZ>= ` F ) ) ) | 
						
							| 24 | 16 22 23 | sylanbrc |  |-  ( ph -> F e. ( 0 ... ( # ` S ) ) ) | 
						
							| 25 |  | pfxlen |  |-  ( ( S e. Word A /\ F e. ( 0 ... ( # ` S ) ) ) -> ( # ` ( S prefix F ) ) = F ) | 
						
							| 26 | 1 24 25 | syl2anc |  |-  ( ph -> ( # ` ( S prefix F ) ) = F ) | 
						
							| 27 | 26 | oveq2d |  |-  ( ph -> ( X + ( # ` ( S prefix F ) ) ) = ( X + F ) ) | 
						
							| 28 | 14 27 | eqtr4d |  |-  ( ph -> ( F + X ) = ( X + ( # ` ( S prefix F ) ) ) ) | 
						
							| 29 | 7 28 | fveq12d |  |-  ( ph -> ( ( S splice <. F , T , R >. ) ` ( F + X ) ) = ( ( ( ( S prefix F ) ++ R ) ++ ( S substr <. T , ( # ` S ) >. ) ) ` ( X + ( # ` ( S prefix F ) ) ) ) ) | 
						
							| 30 |  | pfxcl |  |-  ( S e. Word A -> ( S prefix F ) e. Word A ) | 
						
							| 31 | 1 30 | syl |  |-  ( ph -> ( S prefix F ) e. Word A ) | 
						
							| 32 |  | ccatcl |  |-  ( ( ( S prefix F ) e. Word A /\ R e. Word A ) -> ( ( S prefix F ) ++ R ) e. Word A ) | 
						
							| 33 | 31 4 32 | syl2anc |  |-  ( ph -> ( ( S prefix F ) ++ R ) e. Word A ) | 
						
							| 34 |  | swrdcl |  |-  ( S e. Word A -> ( S substr <. T , ( # ` S ) >. ) e. Word A ) | 
						
							| 35 | 1 34 | syl |  |-  ( ph -> ( S substr <. T , ( # ` S ) >. ) e. Word A ) | 
						
							| 36 |  | 0nn0 |  |-  0 e. NN0 | 
						
							| 37 |  | nn0addcl |  |-  ( ( 0 e. NN0 /\ F e. NN0 ) -> ( 0 + F ) e. NN0 ) | 
						
							| 38 | 36 9 37 | sylancr |  |-  ( ph -> ( 0 + F ) e. NN0 ) | 
						
							| 39 |  | fzoss1 |  |-  ( ( 0 + F ) e. ( ZZ>= ` 0 ) -> ( ( 0 + F ) ..^ ( ( # ` R ) + F ) ) C_ ( 0 ..^ ( ( # ` R ) + F ) ) ) | 
						
							| 40 | 39 15 | eleq2s |  |-  ( ( 0 + F ) e. NN0 -> ( ( 0 + F ) ..^ ( ( # ` R ) + F ) ) C_ ( 0 ..^ ( ( # ` R ) + F ) ) ) | 
						
							| 41 | 38 40 | syl |  |-  ( ph -> ( ( 0 + F ) ..^ ( ( # ` R ) + F ) ) C_ ( 0 ..^ ( ( # ` R ) + F ) ) ) | 
						
							| 42 |  | ccatlen |  |-  ( ( ( S prefix F ) e. Word A /\ R e. Word A ) -> ( # ` ( ( S prefix F ) ++ R ) ) = ( ( # ` ( S prefix F ) ) + ( # ` R ) ) ) | 
						
							| 43 | 31 4 42 | syl2anc |  |-  ( ph -> ( # ` ( ( S prefix F ) ++ R ) ) = ( ( # ` ( S prefix F ) ) + ( # ` R ) ) ) | 
						
							| 44 | 26 | oveq1d |  |-  ( ph -> ( ( # ` ( S prefix F ) ) + ( # ` R ) ) = ( F + ( # ` R ) ) ) | 
						
							| 45 |  | lencl |  |-  ( R e. Word A -> ( # ` R ) e. NN0 ) | 
						
							| 46 | 4 45 | syl |  |-  ( ph -> ( # ` R ) e. NN0 ) | 
						
							| 47 | 46 | nn0cnd |  |-  ( ph -> ( # ` R ) e. CC ) | 
						
							| 48 | 10 47 | addcomd |  |-  ( ph -> ( F + ( # ` R ) ) = ( ( # ` R ) + F ) ) | 
						
							| 49 | 43 44 48 | 3eqtrd |  |-  ( ph -> ( # ` ( ( S prefix F ) ++ R ) ) = ( ( # ` R ) + F ) ) | 
						
							| 50 | 49 | oveq2d |  |-  ( ph -> ( 0 ..^ ( # ` ( ( S prefix F ) ++ R ) ) ) = ( 0 ..^ ( ( # ` R ) + F ) ) ) | 
						
							| 51 | 41 50 | sseqtrrd |  |-  ( ph -> ( ( 0 + F ) ..^ ( ( # ` R ) + F ) ) C_ ( 0 ..^ ( # ` ( ( S prefix F ) ++ R ) ) ) ) | 
						
							| 52 | 9 | nn0zd |  |-  ( ph -> F e. ZZ ) | 
						
							| 53 |  | fzoaddel |  |-  ( ( X e. ( 0 ..^ ( # ` R ) ) /\ F e. ZZ ) -> ( X + F ) e. ( ( 0 + F ) ..^ ( ( # ` R ) + F ) ) ) | 
						
							| 54 | 5 52 53 | syl2anc |  |-  ( ph -> ( X + F ) e. ( ( 0 + F ) ..^ ( ( # ` R ) + F ) ) ) | 
						
							| 55 | 51 54 | sseldd |  |-  ( ph -> ( X + F ) e. ( 0 ..^ ( # ` ( ( S prefix F ) ++ R ) ) ) ) | 
						
							| 56 | 27 55 | eqeltrd |  |-  ( ph -> ( X + ( # ` ( S prefix F ) ) ) e. ( 0 ..^ ( # ` ( ( S prefix F ) ++ R ) ) ) ) | 
						
							| 57 |  | ccatval1 |  |-  ( ( ( ( S prefix F ) ++ R ) e. Word A /\ ( S substr <. T , ( # ` S ) >. ) e. Word A /\ ( X + ( # ` ( S prefix F ) ) ) e. ( 0 ..^ ( # ` ( ( S prefix F ) ++ R ) ) ) ) -> ( ( ( ( S prefix F ) ++ R ) ++ ( S substr <. T , ( # ` S ) >. ) ) ` ( X + ( # ` ( S prefix F ) ) ) ) = ( ( ( S prefix F ) ++ R ) ` ( X + ( # ` ( S prefix F ) ) ) ) ) | 
						
							| 58 | 33 35 56 57 | syl3anc |  |-  ( ph -> ( ( ( ( S prefix F ) ++ R ) ++ ( S substr <. T , ( # ` S ) >. ) ) ` ( X + ( # ` ( S prefix F ) ) ) ) = ( ( ( S prefix F ) ++ R ) ` ( X + ( # ` ( S prefix F ) ) ) ) ) | 
						
							| 59 |  | ccatval3 |  |-  ( ( ( S prefix F ) e. Word A /\ R e. Word A /\ X e. ( 0 ..^ ( # ` R ) ) ) -> ( ( ( S prefix F ) ++ R ) ` ( X + ( # ` ( S prefix F ) ) ) ) = ( R ` X ) ) | 
						
							| 60 | 31 4 5 59 | syl3anc |  |-  ( ph -> ( ( ( S prefix F ) ++ R ) ` ( X + ( # ` ( S prefix F ) ) ) ) = ( R ` X ) ) | 
						
							| 61 | 29 58 60 | 3eqtrd |  |-  ( ph -> ( ( S splice <. F , T , R >. ) ` ( F + X ) ) = ( R ` X ) ) |