| Step | Hyp | Ref | Expression | 
						
							| 1 |  | splfv3.s |  |-  ( ph -> S e. Word A ) | 
						
							| 2 |  | splfv3.f |  |-  ( ph -> F e. ( 0 ... T ) ) | 
						
							| 3 |  | splfv3.t |  |-  ( ph -> T e. ( 0 ... ( # ` S ) ) ) | 
						
							| 4 |  | splfv3.r |  |-  ( ph -> R e. Word A ) | 
						
							| 5 |  | splfv3.x |  |-  ( ph -> X e. ( 0 ..^ ( ( # ` S ) - T ) ) ) | 
						
							| 6 |  | splfv3.k |  |-  ( ph -> K = ( F + ( # ` R ) ) ) | 
						
							| 7 |  | 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 ) >. ) ) ) | 
						
							| 8 | 1 2 3 4 7 | syl13anc |  |-  ( ph -> ( S splice <. F , T , R >. ) = ( ( ( S prefix F ) ++ R ) ++ ( S substr <. T , ( # ` S ) >. ) ) ) | 
						
							| 9 |  | elfzuz3 |  |-  ( T e. ( 0 ... ( # ` S ) ) -> ( # ` S ) e. ( ZZ>= ` T ) ) | 
						
							| 10 |  | fzss2 |  |-  ( ( # ` S ) e. ( ZZ>= ` T ) -> ( 0 ... T ) C_ ( 0 ... ( # ` S ) ) ) | 
						
							| 11 | 3 9 10 | 3syl |  |-  ( ph -> ( 0 ... T ) C_ ( 0 ... ( # ` S ) ) ) | 
						
							| 12 | 11 2 | sseldd |  |-  ( ph -> F e. ( 0 ... ( # ` S ) ) ) | 
						
							| 13 |  | pfxlen |  |-  ( ( S e. Word A /\ F e. ( 0 ... ( # ` S ) ) ) -> ( # ` ( S prefix F ) ) = F ) | 
						
							| 14 | 1 12 13 | syl2anc |  |-  ( ph -> ( # ` ( S prefix F ) ) = F ) | 
						
							| 15 | 14 | oveq1d |  |-  ( ph -> ( ( # ` ( S prefix F ) ) + ( # ` R ) ) = ( F + ( # ` R ) ) ) | 
						
							| 16 |  | pfxcl |  |-  ( S e. Word A -> ( S prefix F ) e. Word A ) | 
						
							| 17 | 1 16 | syl |  |-  ( ph -> ( S prefix F ) e. Word A ) | 
						
							| 18 |  | ccatlen |  |-  ( ( ( S prefix F ) e. Word A /\ R e. Word A ) -> ( # ` ( ( S prefix F ) ++ R ) ) = ( ( # ` ( S prefix F ) ) + ( # ` R ) ) ) | 
						
							| 19 | 17 4 18 | syl2anc |  |-  ( ph -> ( # ` ( ( S prefix F ) ++ R ) ) = ( ( # ` ( S prefix F ) ) + ( # ` R ) ) ) | 
						
							| 20 | 15 19 6 | 3eqtr4rd |  |-  ( ph -> K = ( # ` ( ( S prefix F ) ++ R ) ) ) | 
						
							| 21 | 20 | oveq2d |  |-  ( ph -> ( X + K ) = ( X + ( # ` ( ( S prefix F ) ++ R ) ) ) ) | 
						
							| 22 | 8 21 | fveq12d |  |-  ( ph -> ( ( S splice <. F , T , R >. ) ` ( X + K ) ) = ( ( ( ( S prefix F ) ++ R ) ++ ( S substr <. T , ( # ` S ) >. ) ) ` ( X + ( # ` ( ( S prefix F ) ++ R ) ) ) ) ) | 
						
							| 23 |  | ccatcl |  |-  ( ( ( S prefix F ) e. Word A /\ R e. Word A ) -> ( ( S prefix F ) ++ R ) e. Word A ) | 
						
							| 24 | 17 4 23 | syl2anc |  |-  ( ph -> ( ( S prefix F ) ++ R ) e. Word A ) | 
						
							| 25 |  | swrdcl |  |-  ( S e. Word A -> ( S substr <. T , ( # ` S ) >. ) e. Word A ) | 
						
							| 26 | 1 25 | syl |  |-  ( ph -> ( S substr <. T , ( # ` S ) >. ) e. Word A ) | 
						
							| 27 |  | lencl |  |-  ( S e. Word A -> ( # ` S ) e. NN0 ) | 
						
							| 28 |  | nn0fz0 |  |-  ( ( # ` S ) e. NN0 <-> ( # ` S ) e. ( 0 ... ( # ` S ) ) ) | 
						
							| 29 | 27 28 | sylib |  |-  ( S e. Word A -> ( # ` S ) e. ( 0 ... ( # ` S ) ) ) | 
						
							| 30 | 1 29 | syl |  |-  ( ph -> ( # ` S ) e. ( 0 ... ( # ` S ) ) ) | 
						
							| 31 |  | swrdlen |  |-  ( ( S e. Word A /\ T e. ( 0 ... ( # ` S ) ) /\ ( # ` S ) e. ( 0 ... ( # ` S ) ) ) -> ( # ` ( S substr <. T , ( # ` S ) >. ) ) = ( ( # ` S ) - T ) ) | 
						
							| 32 | 1 3 30 31 | syl3anc |  |-  ( ph -> ( # ` ( S substr <. T , ( # ` S ) >. ) ) = ( ( # ` S ) - T ) ) | 
						
							| 33 | 32 | oveq2d |  |-  ( ph -> ( 0 ..^ ( # ` ( S substr <. T , ( # ` S ) >. ) ) ) = ( 0 ..^ ( ( # ` S ) - T ) ) ) | 
						
							| 34 | 5 33 | eleqtrrd |  |-  ( ph -> X e. ( 0 ..^ ( # ` ( S substr <. T , ( # ` S ) >. ) ) ) ) | 
						
							| 35 |  | ccatval3 |  |-  ( ( ( ( S prefix F ) ++ R ) e. Word A /\ ( S substr <. T , ( # ` S ) >. ) e. Word A /\ X e. ( 0 ..^ ( # ` ( S substr <. T , ( # ` S ) >. ) ) ) ) -> ( ( ( ( S prefix F ) ++ R ) ++ ( S substr <. T , ( # ` S ) >. ) ) ` ( X + ( # ` ( ( S prefix F ) ++ R ) ) ) ) = ( ( S substr <. T , ( # ` S ) >. ) ` X ) ) | 
						
							| 36 | 24 26 34 35 | syl3anc |  |-  ( ph -> ( ( ( ( S prefix F ) ++ R ) ++ ( S substr <. T , ( # ` S ) >. ) ) ` ( X + ( # ` ( ( S prefix F ) ++ R ) ) ) ) = ( ( S substr <. T , ( # ` S ) >. ) ` X ) ) | 
						
							| 37 |  | swrdfv |  |-  ( ( ( S e. Word A /\ T e. ( 0 ... ( # ` S ) ) /\ ( # ` S ) e. ( 0 ... ( # ` S ) ) ) /\ X e. ( 0 ..^ ( ( # ` S ) - T ) ) ) -> ( ( S substr <. T , ( # ` S ) >. ) ` X ) = ( S ` ( X + T ) ) ) | 
						
							| 38 | 1 3 30 5 37 | syl31anc |  |-  ( ph -> ( ( S substr <. T , ( # ` S ) >. ) ` X ) = ( S ` ( X + T ) ) ) | 
						
							| 39 | 22 36 38 | 3eqtrd |  |-  ( ph -> ( ( S splice <. F , T , R >. ) ` ( X + K ) ) = ( S ` ( X + T ) ) ) |