| Step | Hyp | Ref | Expression | 
						
							| 1 |  | spllen.s | ⊢ ( 𝜑  →  𝑆  ∈  Word  𝐴 ) | 
						
							| 2 |  | spllen.f | ⊢ ( 𝜑  →  𝐹  ∈  ( 0 ... 𝑇 ) ) | 
						
							| 3 |  | spllen.t | ⊢ ( 𝜑  →  𝑇  ∈  ( 0 ... ( ♯ ‘ 𝑆 ) ) ) | 
						
							| 4 |  | spllen.r | ⊢ ( 𝜑  →  𝑅  ∈  Word  𝐴 ) | 
						
							| 5 |  | splfv2a.x | ⊢ ( 𝜑  →  𝑋  ∈  ( 0 ..^ ( ♯ ‘ 𝑅 ) ) ) | 
						
							| 6 |  | splval | ⊢ ( ( 𝑆  ∈  Word  𝐴  ∧  ( 𝐹  ∈  ( 0 ... 𝑇 )  ∧  𝑇  ∈  ( 0 ... ( ♯ ‘ 𝑆 ) )  ∧  𝑅  ∈  Word  𝐴 ) )  →  ( 𝑆  splice  〈 𝐹 ,  𝑇 ,  𝑅 〉 )  =  ( ( ( 𝑆  prefix  𝐹 )  ++  𝑅 )  ++  ( 𝑆  substr  〈 𝑇 ,  ( ♯ ‘ 𝑆 ) 〉 ) ) ) | 
						
							| 7 | 1 2 3 4 6 | syl13anc | ⊢ ( 𝜑  →  ( 𝑆  splice  〈 𝐹 ,  𝑇 ,  𝑅 〉 )  =  ( ( ( 𝑆  prefix  𝐹 )  ++  𝑅 )  ++  ( 𝑆  substr  〈 𝑇 ,  ( ♯ ‘ 𝑆 ) 〉 ) ) ) | 
						
							| 8 |  | elfznn0 | ⊢ ( 𝐹  ∈  ( 0 ... 𝑇 )  →  𝐹  ∈  ℕ0 ) | 
						
							| 9 | 2 8 | syl | ⊢ ( 𝜑  →  𝐹  ∈  ℕ0 ) | 
						
							| 10 | 9 | nn0cnd | ⊢ ( 𝜑  →  𝐹  ∈  ℂ ) | 
						
							| 11 |  | elfzonn0 | ⊢ ( 𝑋  ∈  ( 0 ..^ ( ♯ ‘ 𝑅 ) )  →  𝑋  ∈  ℕ0 ) | 
						
							| 12 | 5 11 | syl | ⊢ ( 𝜑  →  𝑋  ∈  ℕ0 ) | 
						
							| 13 | 12 | nn0cnd | ⊢ ( 𝜑  →  𝑋  ∈  ℂ ) | 
						
							| 14 | 10 13 | addcomd | ⊢ ( 𝜑  →  ( 𝐹  +  𝑋 )  =  ( 𝑋  +  𝐹 ) ) | 
						
							| 15 |  | nn0uz | ⊢ ℕ0  =  ( ℤ≥ ‘ 0 ) | 
						
							| 16 | 9 15 | eleqtrdi | ⊢ ( 𝜑  →  𝐹  ∈  ( ℤ≥ ‘ 0 ) ) | 
						
							| 17 |  | elfzuz3 | ⊢ ( 𝑇  ∈  ( 0 ... ( ♯ ‘ 𝑆 ) )  →  ( ♯ ‘ 𝑆 )  ∈  ( ℤ≥ ‘ 𝑇 ) ) | 
						
							| 18 | 3 17 | syl | ⊢ ( 𝜑  →  ( ♯ ‘ 𝑆 )  ∈  ( ℤ≥ ‘ 𝑇 ) ) | 
						
							| 19 |  | elfzuz3 | ⊢ ( 𝐹  ∈  ( 0 ... 𝑇 )  →  𝑇  ∈  ( ℤ≥ ‘ 𝐹 ) ) | 
						
							| 20 | 2 19 | syl | ⊢ ( 𝜑  →  𝑇  ∈  ( ℤ≥ ‘ 𝐹 ) ) | 
						
							| 21 |  | uztrn | ⊢ ( ( ( ♯ ‘ 𝑆 )  ∈  ( ℤ≥ ‘ 𝑇 )  ∧  𝑇  ∈  ( ℤ≥ ‘ 𝐹 ) )  →  ( ♯ ‘ 𝑆 )  ∈  ( ℤ≥ ‘ 𝐹 ) ) | 
						
							| 22 | 18 20 21 | syl2anc | ⊢ ( 𝜑  →  ( ♯ ‘ 𝑆 )  ∈  ( ℤ≥ ‘ 𝐹 ) ) | 
						
							| 23 |  | elfzuzb | ⊢ ( 𝐹  ∈  ( 0 ... ( ♯ ‘ 𝑆 ) )  ↔  ( 𝐹  ∈  ( ℤ≥ ‘ 0 )  ∧  ( ♯ ‘ 𝑆 )  ∈  ( ℤ≥ ‘ 𝐹 ) ) ) | 
						
							| 24 | 16 22 23 | sylanbrc | ⊢ ( 𝜑  →  𝐹  ∈  ( 0 ... ( ♯ ‘ 𝑆 ) ) ) | 
						
							| 25 |  | pfxlen | ⊢ ( ( 𝑆  ∈  Word  𝐴  ∧  𝐹  ∈  ( 0 ... ( ♯ ‘ 𝑆 ) ) )  →  ( ♯ ‘ ( 𝑆  prefix  𝐹 ) )  =  𝐹 ) | 
						
							| 26 | 1 24 25 | syl2anc | ⊢ ( 𝜑  →  ( ♯ ‘ ( 𝑆  prefix  𝐹 ) )  =  𝐹 ) | 
						
							| 27 | 26 | oveq2d | ⊢ ( 𝜑  →  ( 𝑋  +  ( ♯ ‘ ( 𝑆  prefix  𝐹 ) ) )  =  ( 𝑋  +  𝐹 ) ) | 
						
							| 28 | 14 27 | eqtr4d | ⊢ ( 𝜑  →  ( 𝐹  +  𝑋 )  =  ( 𝑋  +  ( ♯ ‘ ( 𝑆  prefix  𝐹 ) ) ) ) | 
						
							| 29 | 7 28 | fveq12d | ⊢ ( 𝜑  →  ( ( 𝑆  splice  〈 𝐹 ,  𝑇 ,  𝑅 〉 ) ‘ ( 𝐹  +  𝑋 ) )  =  ( ( ( ( 𝑆  prefix  𝐹 )  ++  𝑅 )  ++  ( 𝑆  substr  〈 𝑇 ,  ( ♯ ‘ 𝑆 ) 〉 ) ) ‘ ( 𝑋  +  ( ♯ ‘ ( 𝑆  prefix  𝐹 ) ) ) ) ) | 
						
							| 30 |  | pfxcl | ⊢ ( 𝑆  ∈  Word  𝐴  →  ( 𝑆  prefix  𝐹 )  ∈  Word  𝐴 ) | 
						
							| 31 | 1 30 | syl | ⊢ ( 𝜑  →  ( 𝑆  prefix  𝐹 )  ∈  Word  𝐴 ) | 
						
							| 32 |  | ccatcl | ⊢ ( ( ( 𝑆  prefix  𝐹 )  ∈  Word  𝐴  ∧  𝑅  ∈  Word  𝐴 )  →  ( ( 𝑆  prefix  𝐹 )  ++  𝑅 )  ∈  Word  𝐴 ) | 
						
							| 33 | 31 4 32 | syl2anc | ⊢ ( 𝜑  →  ( ( 𝑆  prefix  𝐹 )  ++  𝑅 )  ∈  Word  𝐴 ) | 
						
							| 34 |  | swrdcl | ⊢ ( 𝑆  ∈  Word  𝐴  →  ( 𝑆  substr  〈 𝑇 ,  ( ♯ ‘ 𝑆 ) 〉 )  ∈  Word  𝐴 ) | 
						
							| 35 | 1 34 | syl | ⊢ ( 𝜑  →  ( 𝑆  substr  〈 𝑇 ,  ( ♯ ‘ 𝑆 ) 〉 )  ∈  Word  𝐴 ) | 
						
							| 36 |  | 0nn0 | ⊢ 0  ∈  ℕ0 | 
						
							| 37 |  | nn0addcl | ⊢ ( ( 0  ∈  ℕ0  ∧  𝐹  ∈  ℕ0 )  →  ( 0  +  𝐹 )  ∈  ℕ0 ) | 
						
							| 38 | 36 9 37 | sylancr | ⊢ ( 𝜑  →  ( 0  +  𝐹 )  ∈  ℕ0 ) | 
						
							| 39 |  | fzoss1 | ⊢ ( ( 0  +  𝐹 )  ∈  ( ℤ≥ ‘ 0 )  →  ( ( 0  +  𝐹 ) ..^ ( ( ♯ ‘ 𝑅 )  +  𝐹 ) )  ⊆  ( 0 ..^ ( ( ♯ ‘ 𝑅 )  +  𝐹 ) ) ) | 
						
							| 40 | 39 15 | eleq2s | ⊢ ( ( 0  +  𝐹 )  ∈  ℕ0  →  ( ( 0  +  𝐹 ) ..^ ( ( ♯ ‘ 𝑅 )  +  𝐹 ) )  ⊆  ( 0 ..^ ( ( ♯ ‘ 𝑅 )  +  𝐹 ) ) ) | 
						
							| 41 | 38 40 | syl | ⊢ ( 𝜑  →  ( ( 0  +  𝐹 ) ..^ ( ( ♯ ‘ 𝑅 )  +  𝐹 ) )  ⊆  ( 0 ..^ ( ( ♯ ‘ 𝑅 )  +  𝐹 ) ) ) | 
						
							| 42 |  | ccatlen | ⊢ ( ( ( 𝑆  prefix  𝐹 )  ∈  Word  𝐴  ∧  𝑅  ∈  Word  𝐴 )  →  ( ♯ ‘ ( ( 𝑆  prefix  𝐹 )  ++  𝑅 ) )  =  ( ( ♯ ‘ ( 𝑆  prefix  𝐹 ) )  +  ( ♯ ‘ 𝑅 ) ) ) | 
						
							| 43 | 31 4 42 | syl2anc | ⊢ ( 𝜑  →  ( ♯ ‘ ( ( 𝑆  prefix  𝐹 )  ++  𝑅 ) )  =  ( ( ♯ ‘ ( 𝑆  prefix  𝐹 ) )  +  ( ♯ ‘ 𝑅 ) ) ) | 
						
							| 44 | 26 | oveq1d | ⊢ ( 𝜑  →  ( ( ♯ ‘ ( 𝑆  prefix  𝐹 ) )  +  ( ♯ ‘ 𝑅 ) )  =  ( 𝐹  +  ( ♯ ‘ 𝑅 ) ) ) | 
						
							| 45 |  | lencl | ⊢ ( 𝑅  ∈  Word  𝐴  →  ( ♯ ‘ 𝑅 )  ∈  ℕ0 ) | 
						
							| 46 | 4 45 | syl | ⊢ ( 𝜑  →  ( ♯ ‘ 𝑅 )  ∈  ℕ0 ) | 
						
							| 47 | 46 | nn0cnd | ⊢ ( 𝜑  →  ( ♯ ‘ 𝑅 )  ∈  ℂ ) | 
						
							| 48 | 10 47 | addcomd | ⊢ ( 𝜑  →  ( 𝐹  +  ( ♯ ‘ 𝑅 ) )  =  ( ( ♯ ‘ 𝑅 )  +  𝐹 ) ) | 
						
							| 49 | 43 44 48 | 3eqtrd | ⊢ ( 𝜑  →  ( ♯ ‘ ( ( 𝑆  prefix  𝐹 )  ++  𝑅 ) )  =  ( ( ♯ ‘ 𝑅 )  +  𝐹 ) ) | 
						
							| 50 | 49 | oveq2d | ⊢ ( 𝜑  →  ( 0 ..^ ( ♯ ‘ ( ( 𝑆  prefix  𝐹 )  ++  𝑅 ) ) )  =  ( 0 ..^ ( ( ♯ ‘ 𝑅 )  +  𝐹 ) ) ) | 
						
							| 51 | 41 50 | sseqtrrd | ⊢ ( 𝜑  →  ( ( 0  +  𝐹 ) ..^ ( ( ♯ ‘ 𝑅 )  +  𝐹 ) )  ⊆  ( 0 ..^ ( ♯ ‘ ( ( 𝑆  prefix  𝐹 )  ++  𝑅 ) ) ) ) | 
						
							| 52 | 9 | nn0zd | ⊢ ( 𝜑  →  𝐹  ∈  ℤ ) | 
						
							| 53 |  | fzoaddel | ⊢ ( ( 𝑋  ∈  ( 0 ..^ ( ♯ ‘ 𝑅 ) )  ∧  𝐹  ∈  ℤ )  →  ( 𝑋  +  𝐹 )  ∈  ( ( 0  +  𝐹 ) ..^ ( ( ♯ ‘ 𝑅 )  +  𝐹 ) ) ) | 
						
							| 54 | 5 52 53 | syl2anc | ⊢ ( 𝜑  →  ( 𝑋  +  𝐹 )  ∈  ( ( 0  +  𝐹 ) ..^ ( ( ♯ ‘ 𝑅 )  +  𝐹 ) ) ) | 
						
							| 55 | 51 54 | sseldd | ⊢ ( 𝜑  →  ( 𝑋  +  𝐹 )  ∈  ( 0 ..^ ( ♯ ‘ ( ( 𝑆  prefix  𝐹 )  ++  𝑅 ) ) ) ) | 
						
							| 56 | 27 55 | eqeltrd | ⊢ ( 𝜑  →  ( 𝑋  +  ( ♯ ‘ ( 𝑆  prefix  𝐹 ) ) )  ∈  ( 0 ..^ ( ♯ ‘ ( ( 𝑆  prefix  𝐹 )  ++  𝑅 ) ) ) ) | 
						
							| 57 |  | ccatval1 | ⊢ ( ( ( ( 𝑆  prefix  𝐹 )  ++  𝑅 )  ∈  Word  𝐴  ∧  ( 𝑆  substr  〈 𝑇 ,  ( ♯ ‘ 𝑆 ) 〉 )  ∈  Word  𝐴  ∧  ( 𝑋  +  ( ♯ ‘ ( 𝑆  prefix  𝐹 ) ) )  ∈  ( 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 | ⊢ ( 𝜑  →  ( ( ( ( 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 )  ∈  Word  𝐴  ∧  𝑅  ∈  Word  𝐴  ∧  𝑋  ∈  ( 0 ..^ ( ♯ ‘ 𝑅 ) ) )  →  ( ( ( 𝑆  prefix  𝐹 )  ++  𝑅 ) ‘ ( 𝑋  +  ( ♯ ‘ ( 𝑆  prefix  𝐹 ) ) ) )  =  ( 𝑅 ‘ 𝑋 ) ) | 
						
							| 60 | 31 4 5 59 | syl3anc | ⊢ ( 𝜑  →  ( ( ( 𝑆  prefix  𝐹 )  ++  𝑅 ) ‘ ( 𝑋  +  ( ♯ ‘ ( 𝑆  prefix  𝐹 ) ) ) )  =  ( 𝑅 ‘ 𝑋 ) ) | 
						
							| 61 | 29 58 60 | 3eqtrd | ⊢ ( 𝜑  →  ( ( 𝑆  splice  〈 𝐹 ,  𝑇 ,  𝑅 〉 ) ‘ ( 𝐹  +  𝑋 ) )  =  ( 𝑅 ‘ 𝑋 ) ) |