| Step | Hyp | Ref | Expression | 
						
							| 1 |  | gsumspl.b | ⊢ 𝐵  =  ( Base ‘ 𝑀 ) | 
						
							| 2 |  | gsumspl.m | ⊢ ( 𝜑  →  𝑀  ∈  Mnd ) | 
						
							| 3 |  | gsumspl.s | ⊢ ( 𝜑  →  𝑆  ∈  Word  𝐵 ) | 
						
							| 4 |  | gsumspl.f | ⊢ ( 𝜑  →  𝐹  ∈  ( 0 ... 𝑇 ) ) | 
						
							| 5 |  | gsumspl.t | ⊢ ( 𝜑  →  𝑇  ∈  ( 0 ... ( ♯ ‘ 𝑆 ) ) ) | 
						
							| 6 |  | gsumspl.x | ⊢ ( 𝜑  →  𝑋  ∈  Word  𝐵 ) | 
						
							| 7 |  | gsumspl.y | ⊢ ( 𝜑  →  𝑌  ∈  Word  𝐵 ) | 
						
							| 8 |  | gsumspl.eq | ⊢ ( 𝜑  →  ( 𝑀  Σg  𝑋 )  =  ( 𝑀  Σg  𝑌 ) ) | 
						
							| 9 | 8 | oveq2d | ⊢ ( 𝜑  →  ( ( 𝑀  Σg  ( 𝑆  prefix  𝐹 ) ) ( +g ‘ 𝑀 ) ( 𝑀  Σg  𝑋 ) )  =  ( ( 𝑀  Σg  ( 𝑆  prefix  𝐹 ) ) ( +g ‘ 𝑀 ) ( 𝑀  Σg  𝑌 ) ) ) | 
						
							| 10 | 9 | oveq1d | ⊢ ( 𝜑  →  ( ( ( 𝑀  Σg  ( 𝑆  prefix  𝐹 ) ) ( +g ‘ 𝑀 ) ( 𝑀  Σg  𝑋 ) ) ( +g ‘ 𝑀 ) ( 𝑀  Σg  ( 𝑆  substr  〈 𝑇 ,  ( ♯ ‘ 𝑆 ) 〉 ) ) )  =  ( ( ( 𝑀  Σg  ( 𝑆  prefix  𝐹 ) ) ( +g ‘ 𝑀 ) ( 𝑀  Σg  𝑌 ) ) ( +g ‘ 𝑀 ) ( 𝑀  Σg  ( 𝑆  substr  〈 𝑇 ,  ( ♯ ‘ 𝑆 ) 〉 ) ) ) ) | 
						
							| 11 |  | splval | ⊢ ( ( 𝑆  ∈  Word  𝐵  ∧  ( 𝐹  ∈  ( 0 ... 𝑇 )  ∧  𝑇  ∈  ( 0 ... ( ♯ ‘ 𝑆 ) )  ∧  𝑋  ∈  Word  𝐵 ) )  →  ( 𝑆  splice  〈 𝐹 ,  𝑇 ,  𝑋 〉 )  =  ( ( ( 𝑆  prefix  𝐹 )  ++  𝑋 )  ++  ( 𝑆  substr  〈 𝑇 ,  ( ♯ ‘ 𝑆 ) 〉 ) ) ) | 
						
							| 12 | 3 4 5 6 11 | syl13anc | ⊢ ( 𝜑  →  ( 𝑆  splice  〈 𝐹 ,  𝑇 ,  𝑋 〉 )  =  ( ( ( 𝑆  prefix  𝐹 )  ++  𝑋 )  ++  ( 𝑆  substr  〈 𝑇 ,  ( ♯ ‘ 𝑆 ) 〉 ) ) ) | 
						
							| 13 | 12 | oveq2d | ⊢ ( 𝜑  →  ( 𝑀  Σg  ( 𝑆  splice  〈 𝐹 ,  𝑇 ,  𝑋 〉 ) )  =  ( 𝑀  Σg  ( ( ( 𝑆  prefix  𝐹 )  ++  𝑋 )  ++  ( 𝑆  substr  〈 𝑇 ,  ( ♯ ‘ 𝑆 ) 〉 ) ) ) ) | 
						
							| 14 |  | pfxcl | ⊢ ( 𝑆  ∈  Word  𝐵  →  ( 𝑆  prefix  𝐹 )  ∈  Word  𝐵 ) | 
						
							| 15 | 3 14 | syl | ⊢ ( 𝜑  →  ( 𝑆  prefix  𝐹 )  ∈  Word  𝐵 ) | 
						
							| 16 |  | ccatcl | ⊢ ( ( ( 𝑆  prefix  𝐹 )  ∈  Word  𝐵  ∧  𝑋  ∈  Word  𝐵 )  →  ( ( 𝑆  prefix  𝐹 )  ++  𝑋 )  ∈  Word  𝐵 ) | 
						
							| 17 | 15 6 16 | syl2anc | ⊢ ( 𝜑  →  ( ( 𝑆  prefix  𝐹 )  ++  𝑋 )  ∈  Word  𝐵 ) | 
						
							| 18 |  | swrdcl | ⊢ ( 𝑆  ∈  Word  𝐵  →  ( 𝑆  substr  〈 𝑇 ,  ( ♯ ‘ 𝑆 ) 〉 )  ∈  Word  𝐵 ) | 
						
							| 19 | 3 18 | syl | ⊢ ( 𝜑  →  ( 𝑆  substr  〈 𝑇 ,  ( ♯ ‘ 𝑆 ) 〉 )  ∈  Word  𝐵 ) | 
						
							| 20 |  | eqid | ⊢ ( +g ‘ 𝑀 )  =  ( +g ‘ 𝑀 ) | 
						
							| 21 | 1 20 | gsumccat | ⊢ ( ( 𝑀  ∈  Mnd  ∧  ( ( 𝑆  prefix  𝐹 )  ++  𝑋 )  ∈  Word  𝐵  ∧  ( 𝑆  substr  〈 𝑇 ,  ( ♯ ‘ 𝑆 ) 〉 )  ∈  Word  𝐵 )  →  ( 𝑀  Σg  ( ( ( 𝑆  prefix  𝐹 )  ++  𝑋 )  ++  ( 𝑆  substr  〈 𝑇 ,  ( ♯ ‘ 𝑆 ) 〉 ) ) )  =  ( ( 𝑀  Σg  ( ( 𝑆  prefix  𝐹 )  ++  𝑋 ) ) ( +g ‘ 𝑀 ) ( 𝑀  Σg  ( 𝑆  substr  〈 𝑇 ,  ( ♯ ‘ 𝑆 ) 〉 ) ) ) ) | 
						
							| 22 | 2 17 19 21 | syl3anc | ⊢ ( 𝜑  →  ( 𝑀  Σg  ( ( ( 𝑆  prefix  𝐹 )  ++  𝑋 )  ++  ( 𝑆  substr  〈 𝑇 ,  ( ♯ ‘ 𝑆 ) 〉 ) ) )  =  ( ( 𝑀  Σg  ( ( 𝑆  prefix  𝐹 )  ++  𝑋 ) ) ( +g ‘ 𝑀 ) ( 𝑀  Σg  ( 𝑆  substr  〈 𝑇 ,  ( ♯ ‘ 𝑆 ) 〉 ) ) ) ) | 
						
							| 23 | 1 20 | gsumccat | ⊢ ( ( 𝑀  ∈  Mnd  ∧  ( 𝑆  prefix  𝐹 )  ∈  Word  𝐵  ∧  𝑋  ∈  Word  𝐵 )  →  ( 𝑀  Σg  ( ( 𝑆  prefix  𝐹 )  ++  𝑋 ) )  =  ( ( 𝑀  Σg  ( 𝑆  prefix  𝐹 ) ) ( +g ‘ 𝑀 ) ( 𝑀  Σg  𝑋 ) ) ) | 
						
							| 24 | 2 15 6 23 | syl3anc | ⊢ ( 𝜑  →  ( 𝑀  Σg  ( ( 𝑆  prefix  𝐹 )  ++  𝑋 ) )  =  ( ( 𝑀  Σg  ( 𝑆  prefix  𝐹 ) ) ( +g ‘ 𝑀 ) ( 𝑀  Σg  𝑋 ) ) ) | 
						
							| 25 | 24 | oveq1d | ⊢ ( 𝜑  →  ( ( 𝑀  Σg  ( ( 𝑆  prefix  𝐹 )  ++  𝑋 ) ) ( +g ‘ 𝑀 ) ( 𝑀  Σg  ( 𝑆  substr  〈 𝑇 ,  ( ♯ ‘ 𝑆 ) 〉 ) ) )  =  ( ( ( 𝑀  Σg  ( 𝑆  prefix  𝐹 ) ) ( +g ‘ 𝑀 ) ( 𝑀  Σg  𝑋 ) ) ( +g ‘ 𝑀 ) ( 𝑀  Σg  ( 𝑆  substr  〈 𝑇 ,  ( ♯ ‘ 𝑆 ) 〉 ) ) ) ) | 
						
							| 26 | 13 22 25 | 3eqtrd | ⊢ ( 𝜑  →  ( 𝑀  Σg  ( 𝑆  splice  〈 𝐹 ,  𝑇 ,  𝑋 〉 ) )  =  ( ( ( 𝑀  Σg  ( 𝑆  prefix  𝐹 ) ) ( +g ‘ 𝑀 ) ( 𝑀  Σg  𝑋 ) ) ( +g ‘ 𝑀 ) ( 𝑀  Σg  ( 𝑆  substr  〈 𝑇 ,  ( ♯ ‘ 𝑆 ) 〉 ) ) ) ) | 
						
							| 27 |  | splval | ⊢ ( ( 𝑆  ∈  Word  𝐵  ∧  ( 𝐹  ∈  ( 0 ... 𝑇 )  ∧  𝑇  ∈  ( 0 ... ( ♯ ‘ 𝑆 ) )  ∧  𝑌  ∈  Word  𝐵 ) )  →  ( 𝑆  splice  〈 𝐹 ,  𝑇 ,  𝑌 〉 )  =  ( ( ( 𝑆  prefix  𝐹 )  ++  𝑌 )  ++  ( 𝑆  substr  〈 𝑇 ,  ( ♯ ‘ 𝑆 ) 〉 ) ) ) | 
						
							| 28 | 3 4 5 7 27 | syl13anc | ⊢ ( 𝜑  →  ( 𝑆  splice  〈 𝐹 ,  𝑇 ,  𝑌 〉 )  =  ( ( ( 𝑆  prefix  𝐹 )  ++  𝑌 )  ++  ( 𝑆  substr  〈 𝑇 ,  ( ♯ ‘ 𝑆 ) 〉 ) ) ) | 
						
							| 29 | 28 | oveq2d | ⊢ ( 𝜑  →  ( 𝑀  Σg  ( 𝑆  splice  〈 𝐹 ,  𝑇 ,  𝑌 〉 ) )  =  ( 𝑀  Σg  ( ( ( 𝑆  prefix  𝐹 )  ++  𝑌 )  ++  ( 𝑆  substr  〈 𝑇 ,  ( ♯ ‘ 𝑆 ) 〉 ) ) ) ) | 
						
							| 30 |  | ccatcl | ⊢ ( ( ( 𝑆  prefix  𝐹 )  ∈  Word  𝐵  ∧  𝑌  ∈  Word  𝐵 )  →  ( ( 𝑆  prefix  𝐹 )  ++  𝑌 )  ∈  Word  𝐵 ) | 
						
							| 31 | 15 7 30 | syl2anc | ⊢ ( 𝜑  →  ( ( 𝑆  prefix  𝐹 )  ++  𝑌 )  ∈  Word  𝐵 ) | 
						
							| 32 | 1 20 | gsumccat | ⊢ ( ( 𝑀  ∈  Mnd  ∧  ( ( 𝑆  prefix  𝐹 )  ++  𝑌 )  ∈  Word  𝐵  ∧  ( 𝑆  substr  〈 𝑇 ,  ( ♯ ‘ 𝑆 ) 〉 )  ∈  Word  𝐵 )  →  ( 𝑀  Σg  ( ( ( 𝑆  prefix  𝐹 )  ++  𝑌 )  ++  ( 𝑆  substr  〈 𝑇 ,  ( ♯ ‘ 𝑆 ) 〉 ) ) )  =  ( ( 𝑀  Σg  ( ( 𝑆  prefix  𝐹 )  ++  𝑌 ) ) ( +g ‘ 𝑀 ) ( 𝑀  Σg  ( 𝑆  substr  〈 𝑇 ,  ( ♯ ‘ 𝑆 ) 〉 ) ) ) ) | 
						
							| 33 | 2 31 19 32 | syl3anc | ⊢ ( 𝜑  →  ( 𝑀  Σg  ( ( ( 𝑆  prefix  𝐹 )  ++  𝑌 )  ++  ( 𝑆  substr  〈 𝑇 ,  ( ♯ ‘ 𝑆 ) 〉 ) ) )  =  ( ( 𝑀  Σg  ( ( 𝑆  prefix  𝐹 )  ++  𝑌 ) ) ( +g ‘ 𝑀 ) ( 𝑀  Σg  ( 𝑆  substr  〈 𝑇 ,  ( ♯ ‘ 𝑆 ) 〉 ) ) ) ) | 
						
							| 34 | 1 20 | gsumccat | ⊢ ( ( 𝑀  ∈  Mnd  ∧  ( 𝑆  prefix  𝐹 )  ∈  Word  𝐵  ∧  𝑌  ∈  Word  𝐵 )  →  ( 𝑀  Σg  ( ( 𝑆  prefix  𝐹 )  ++  𝑌 ) )  =  ( ( 𝑀  Σg  ( 𝑆  prefix  𝐹 ) ) ( +g ‘ 𝑀 ) ( 𝑀  Σg  𝑌 ) ) ) | 
						
							| 35 | 2 15 7 34 | syl3anc | ⊢ ( 𝜑  →  ( 𝑀  Σg  ( ( 𝑆  prefix  𝐹 )  ++  𝑌 ) )  =  ( ( 𝑀  Σg  ( 𝑆  prefix  𝐹 ) ) ( +g ‘ 𝑀 ) ( 𝑀  Σg  𝑌 ) ) ) | 
						
							| 36 | 35 | oveq1d | ⊢ ( 𝜑  →  ( ( 𝑀  Σg  ( ( 𝑆  prefix  𝐹 )  ++  𝑌 ) ) ( +g ‘ 𝑀 ) ( 𝑀  Σg  ( 𝑆  substr  〈 𝑇 ,  ( ♯ ‘ 𝑆 ) 〉 ) ) )  =  ( ( ( 𝑀  Σg  ( 𝑆  prefix  𝐹 ) ) ( +g ‘ 𝑀 ) ( 𝑀  Σg  𝑌 ) ) ( +g ‘ 𝑀 ) ( 𝑀  Σg  ( 𝑆  substr  〈 𝑇 ,  ( ♯ ‘ 𝑆 ) 〉 ) ) ) ) | 
						
							| 37 | 29 33 36 | 3eqtrd | ⊢ ( 𝜑  →  ( 𝑀  Σg  ( 𝑆  splice  〈 𝐹 ,  𝑇 ,  𝑌 〉 ) )  =  ( ( ( 𝑀  Σg  ( 𝑆  prefix  𝐹 ) ) ( +g ‘ 𝑀 ) ( 𝑀  Σg  𝑌 ) ) ( +g ‘ 𝑀 ) ( 𝑀  Σg  ( 𝑆  substr  〈 𝑇 ,  ( ♯ ‘ 𝑆 ) 〉 ) ) ) ) | 
						
							| 38 | 10 26 37 | 3eqtr4d | ⊢ ( 𝜑  →  ( 𝑀  Σg  ( 𝑆  splice  〈 𝐹 ,  𝑇 ,  𝑋 〉 ) )  =  ( 𝑀  Σg  ( 𝑆  splice  〈 𝐹 ,  𝑇 ,  𝑌 〉 ) ) ) |