| Step | Hyp | Ref | Expression | 
						
							| 1 |  | splval2.a |  |-  ( ph -> A e. Word X ) | 
						
							| 2 |  | splval2.b |  |-  ( ph -> B e. Word X ) | 
						
							| 3 |  | splval2.c |  |-  ( ph -> C e. Word X ) | 
						
							| 4 |  | splval2.r |  |-  ( ph -> R e. Word X ) | 
						
							| 5 |  | splval2.s |  |-  ( ph -> S = ( ( A ++ B ) ++ C ) ) | 
						
							| 6 |  | splval2.f |  |-  ( ph -> F = ( # ` A ) ) | 
						
							| 7 |  | splval2.t |  |-  ( ph -> T = ( F + ( # ` B ) ) ) | 
						
							| 8 |  | ccatcl |  |-  ( ( A e. Word X /\ B e. Word X ) -> ( A ++ B ) e. Word X ) | 
						
							| 9 | 1 2 8 | syl2anc |  |-  ( ph -> ( A ++ B ) e. Word X ) | 
						
							| 10 |  | ccatcl |  |-  ( ( ( A ++ B ) e. Word X /\ C e. Word X ) -> ( ( A ++ B ) ++ C ) e. Word X ) | 
						
							| 11 | 9 3 10 | syl2anc |  |-  ( ph -> ( ( A ++ B ) ++ C ) e. Word X ) | 
						
							| 12 | 5 11 | eqeltrd |  |-  ( ph -> S e. Word X ) | 
						
							| 13 |  | lencl |  |-  ( A e. Word X -> ( # ` A ) e. NN0 ) | 
						
							| 14 | 1 13 | syl |  |-  ( ph -> ( # ` A ) e. NN0 ) | 
						
							| 15 | 6 14 | eqeltrd |  |-  ( ph -> F e. NN0 ) | 
						
							| 16 |  | lencl |  |-  ( B e. Word X -> ( # ` B ) e. NN0 ) | 
						
							| 17 | 2 16 | syl |  |-  ( ph -> ( # ` B ) e. NN0 ) | 
						
							| 18 | 15 17 | nn0addcld |  |-  ( ph -> ( F + ( # ` B ) ) e. NN0 ) | 
						
							| 19 | 7 18 | eqeltrd |  |-  ( ph -> T e. NN0 ) | 
						
							| 20 |  | splval |  |-  ( ( S e. Word X /\ ( F e. NN0 /\ T e. NN0 /\ R e. Word X ) ) -> ( S splice <. F , T , R >. ) = ( ( ( S prefix F ) ++ R ) ++ ( S substr <. T , ( # ` S ) >. ) ) ) | 
						
							| 21 | 12 15 19 4 20 | syl13anc |  |-  ( ph -> ( S splice <. F , T , R >. ) = ( ( ( S prefix F ) ++ R ) ++ ( S substr <. T , ( # ` S ) >. ) ) ) | 
						
							| 22 |  | nn0uz |  |-  NN0 = ( ZZ>= ` 0 ) | 
						
							| 23 | 15 22 | eleqtrdi |  |-  ( ph -> F e. ( ZZ>= ` 0 ) ) | 
						
							| 24 | 15 | nn0zd |  |-  ( ph -> F e. ZZ ) | 
						
							| 25 | 24 | uzidd |  |-  ( ph -> F e. ( ZZ>= ` F ) ) | 
						
							| 26 |  | uzaddcl |  |-  ( ( F e. ( ZZ>= ` F ) /\ ( # ` B ) e. NN0 ) -> ( F + ( # ` B ) ) e. ( ZZ>= ` F ) ) | 
						
							| 27 | 25 17 26 | syl2anc |  |-  ( ph -> ( F + ( # ` B ) ) e. ( ZZ>= ` F ) ) | 
						
							| 28 | 7 27 | eqeltrd |  |-  ( ph -> T e. ( ZZ>= ` F ) ) | 
						
							| 29 |  | elfzuzb |  |-  ( F e. ( 0 ... T ) <-> ( F e. ( ZZ>= ` 0 ) /\ T e. ( ZZ>= ` F ) ) ) | 
						
							| 30 | 23 28 29 | sylanbrc |  |-  ( ph -> F e. ( 0 ... T ) ) | 
						
							| 31 | 19 22 | eleqtrdi |  |-  ( ph -> T e. ( ZZ>= ` 0 ) ) | 
						
							| 32 |  | ccatlen |  |-  ( ( ( A ++ B ) e. Word X /\ C e. Word X ) -> ( # ` ( ( A ++ B ) ++ C ) ) = ( ( # ` ( A ++ B ) ) + ( # ` C ) ) ) | 
						
							| 33 | 9 3 32 | syl2anc |  |-  ( ph -> ( # ` ( ( A ++ B ) ++ C ) ) = ( ( # ` ( A ++ B ) ) + ( # ` C ) ) ) | 
						
							| 34 | 5 | fveq2d |  |-  ( ph -> ( # ` S ) = ( # ` ( ( A ++ B ) ++ C ) ) ) | 
						
							| 35 | 6 | oveq1d |  |-  ( ph -> ( F + ( # ` B ) ) = ( ( # ` A ) + ( # ` B ) ) ) | 
						
							| 36 |  | ccatlen |  |-  ( ( A e. Word X /\ B e. Word X ) -> ( # ` ( A ++ B ) ) = ( ( # ` A ) + ( # ` B ) ) ) | 
						
							| 37 | 1 2 36 | syl2anc |  |-  ( ph -> ( # ` ( A ++ B ) ) = ( ( # ` A ) + ( # ` B ) ) ) | 
						
							| 38 | 35 7 37 | 3eqtr4d |  |-  ( ph -> T = ( # ` ( A ++ B ) ) ) | 
						
							| 39 | 38 | oveq1d |  |-  ( ph -> ( T + ( # ` C ) ) = ( ( # ` ( A ++ B ) ) + ( # ` C ) ) ) | 
						
							| 40 | 33 34 39 | 3eqtr4d |  |-  ( ph -> ( # ` S ) = ( T + ( # ` C ) ) ) | 
						
							| 41 | 19 | nn0zd |  |-  ( ph -> T e. ZZ ) | 
						
							| 42 | 41 | uzidd |  |-  ( ph -> T e. ( ZZ>= ` T ) ) | 
						
							| 43 |  | lencl |  |-  ( C e. Word X -> ( # ` C ) e. NN0 ) | 
						
							| 44 | 3 43 | syl |  |-  ( ph -> ( # ` C ) e. NN0 ) | 
						
							| 45 |  | uzaddcl |  |-  ( ( T e. ( ZZ>= ` T ) /\ ( # ` C ) e. NN0 ) -> ( T + ( # ` C ) ) e. ( ZZ>= ` T ) ) | 
						
							| 46 | 42 44 45 | syl2anc |  |-  ( ph -> ( T + ( # ` C ) ) e. ( ZZ>= ` T ) ) | 
						
							| 47 | 40 46 | eqeltrd |  |-  ( ph -> ( # ` S ) e. ( ZZ>= ` T ) ) | 
						
							| 48 |  | elfzuzb |  |-  ( T e. ( 0 ... ( # ` S ) ) <-> ( T e. ( ZZ>= ` 0 ) /\ ( # ` S ) e. ( ZZ>= ` T ) ) ) | 
						
							| 49 | 31 47 48 | sylanbrc |  |-  ( ph -> T e. ( 0 ... ( # ` S ) ) ) | 
						
							| 50 |  | ccatpfx |  |-  ( ( S e. Word X /\ F e. ( 0 ... T ) /\ T e. ( 0 ... ( # ` S ) ) ) -> ( ( S prefix F ) ++ ( S substr <. F , T >. ) ) = ( S prefix T ) ) | 
						
							| 51 | 12 30 49 50 | syl3anc |  |-  ( ph -> ( ( S prefix F ) ++ ( S substr <. F , T >. ) ) = ( S prefix T ) ) | 
						
							| 52 |  | lencl |  |-  ( S e. Word X -> ( # ` S ) e. NN0 ) | 
						
							| 53 | 12 52 | syl |  |-  ( ph -> ( # ` S ) e. NN0 ) | 
						
							| 54 | 53 22 | eleqtrdi |  |-  ( ph -> ( # ` S ) e. ( ZZ>= ` 0 ) ) | 
						
							| 55 |  | eluzfz2 |  |-  ( ( # ` S ) e. ( ZZ>= ` 0 ) -> ( # ` S ) e. ( 0 ... ( # ` S ) ) ) | 
						
							| 56 | 54 55 | syl |  |-  ( ph -> ( # ` S ) e. ( 0 ... ( # ` S ) ) ) | 
						
							| 57 |  | ccatpfx |  |-  ( ( S e. Word X /\ T e. ( 0 ... ( # ` S ) ) /\ ( # ` S ) e. ( 0 ... ( # ` S ) ) ) -> ( ( S prefix T ) ++ ( S substr <. T , ( # ` S ) >. ) ) = ( S prefix ( # ` S ) ) ) | 
						
							| 58 | 12 49 56 57 | syl3anc |  |-  ( ph -> ( ( S prefix T ) ++ ( S substr <. T , ( # ` S ) >. ) ) = ( S prefix ( # ` S ) ) ) | 
						
							| 59 |  | pfxid |  |-  ( S e. Word X -> ( S prefix ( # ` S ) ) = S ) | 
						
							| 60 | 12 59 | syl |  |-  ( ph -> ( S prefix ( # ` S ) ) = S ) | 
						
							| 61 | 58 60 5 | 3eqtrd |  |-  ( ph -> ( ( S prefix T ) ++ ( S substr <. T , ( # ` S ) >. ) ) = ( ( A ++ B ) ++ C ) ) | 
						
							| 62 |  | pfxcl |  |-  ( S e. Word X -> ( S prefix T ) e. Word X ) | 
						
							| 63 | 12 62 | syl |  |-  ( ph -> ( S prefix T ) e. Word X ) | 
						
							| 64 |  | swrdcl |  |-  ( S e. Word X -> ( S substr <. T , ( # ` S ) >. ) e. Word X ) | 
						
							| 65 | 12 64 | syl |  |-  ( ph -> ( S substr <. T , ( # ` S ) >. ) e. Word X ) | 
						
							| 66 |  | pfxlen |  |-  ( ( S e. Word X /\ T e. ( 0 ... ( # ` S ) ) ) -> ( # ` ( S prefix T ) ) = T ) | 
						
							| 67 | 12 49 66 | syl2anc |  |-  ( ph -> ( # ` ( S prefix T ) ) = T ) | 
						
							| 68 | 67 38 | eqtrd |  |-  ( ph -> ( # ` ( S prefix T ) ) = ( # ` ( A ++ B ) ) ) | 
						
							| 69 |  | ccatopth |  |-  ( ( ( ( S prefix T ) e. Word X /\ ( S substr <. T , ( # ` S ) >. ) e. Word X ) /\ ( ( A ++ B ) e. Word X /\ C e. Word X ) /\ ( # ` ( S prefix T ) ) = ( # ` ( A ++ B ) ) ) -> ( ( ( S prefix T ) ++ ( S substr <. T , ( # ` S ) >. ) ) = ( ( A ++ B ) ++ C ) <-> ( ( S prefix T ) = ( A ++ B ) /\ ( S substr <. T , ( # ` S ) >. ) = C ) ) ) | 
						
							| 70 | 63 65 9 3 68 69 | syl221anc |  |-  ( ph -> ( ( ( S prefix T ) ++ ( S substr <. T , ( # ` S ) >. ) ) = ( ( A ++ B ) ++ C ) <-> ( ( S prefix T ) = ( A ++ B ) /\ ( S substr <. T , ( # ` S ) >. ) = C ) ) ) | 
						
							| 71 | 61 70 | mpbid |  |-  ( ph -> ( ( S prefix T ) = ( A ++ B ) /\ ( S substr <. T , ( # ` S ) >. ) = C ) ) | 
						
							| 72 | 71 | simpld |  |-  ( ph -> ( S prefix T ) = ( A ++ B ) ) | 
						
							| 73 | 51 72 | eqtrd |  |-  ( ph -> ( ( S prefix F ) ++ ( S substr <. F , T >. ) ) = ( A ++ B ) ) | 
						
							| 74 |  | pfxcl |  |-  ( S e. Word X -> ( S prefix F ) e. Word X ) | 
						
							| 75 | 12 74 | syl |  |-  ( ph -> ( S prefix F ) e. Word X ) | 
						
							| 76 |  | swrdcl |  |-  ( S e. Word X -> ( S substr <. F , T >. ) e. Word X ) | 
						
							| 77 | 12 76 | syl |  |-  ( ph -> ( S substr <. F , T >. ) e. Word X ) | 
						
							| 78 |  | uztrn |  |-  ( ( ( # ` S ) e. ( ZZ>= ` T ) /\ T e. ( ZZ>= ` F ) ) -> ( # ` S ) e. ( ZZ>= ` F ) ) | 
						
							| 79 | 47 28 78 | syl2anc |  |-  ( ph -> ( # ` S ) e. ( ZZ>= ` F ) ) | 
						
							| 80 |  | elfzuzb |  |-  ( F e. ( 0 ... ( # ` S ) ) <-> ( F e. ( ZZ>= ` 0 ) /\ ( # ` S ) e. ( ZZ>= ` F ) ) ) | 
						
							| 81 | 23 79 80 | sylanbrc |  |-  ( ph -> F e. ( 0 ... ( # ` S ) ) ) | 
						
							| 82 |  | pfxlen |  |-  ( ( S e. Word X /\ F e. ( 0 ... ( # ` S ) ) ) -> ( # ` ( S prefix F ) ) = F ) | 
						
							| 83 | 12 81 82 | syl2anc |  |-  ( ph -> ( # ` ( S prefix F ) ) = F ) | 
						
							| 84 | 83 6 | eqtrd |  |-  ( ph -> ( # ` ( S prefix F ) ) = ( # ` A ) ) | 
						
							| 85 |  | ccatopth |  |-  ( ( ( ( S prefix F ) e. Word X /\ ( S substr <. F , T >. ) e. Word X ) /\ ( A e. Word X /\ B e. Word X ) /\ ( # ` ( S prefix F ) ) = ( # ` A ) ) -> ( ( ( S prefix F ) ++ ( S substr <. F , T >. ) ) = ( A ++ B ) <-> ( ( S prefix F ) = A /\ ( S substr <. F , T >. ) = B ) ) ) | 
						
							| 86 | 75 77 1 2 84 85 | syl221anc |  |-  ( ph -> ( ( ( S prefix F ) ++ ( S substr <. F , T >. ) ) = ( A ++ B ) <-> ( ( S prefix F ) = A /\ ( S substr <. F , T >. ) = B ) ) ) | 
						
							| 87 | 73 86 | mpbid |  |-  ( ph -> ( ( S prefix F ) = A /\ ( S substr <. F , T >. ) = B ) ) | 
						
							| 88 | 87 | simpld |  |-  ( ph -> ( S prefix F ) = A ) | 
						
							| 89 | 88 | oveq1d |  |-  ( ph -> ( ( S prefix F ) ++ R ) = ( A ++ R ) ) | 
						
							| 90 | 71 | simprd |  |-  ( ph -> ( S substr <. T , ( # ` S ) >. ) = C ) | 
						
							| 91 | 89 90 | oveq12d |  |-  ( ph -> ( ( ( S prefix F ) ++ R ) ++ ( S substr <. T , ( # ` S ) >. ) ) = ( ( A ++ R ) ++ C ) ) | 
						
							| 92 | 21 91 | eqtrd |  |-  ( ph -> ( S splice <. F , T , R >. ) = ( ( A ++ R ) ++ C ) ) |