| Step | Hyp | Ref | Expression | 
						
							| 1 |  | estrcbas.c | ⊢ 𝐶  =  ( ExtStrCat ‘ 𝑈 ) | 
						
							| 2 |  | estrcbas.u | ⊢ ( 𝜑  →  𝑈  ∈  𝑉 ) | 
						
							| 3 |  | estrchomfval.h | ⊢ 𝐻  =  ( Hom  ‘ 𝐶 ) | 
						
							| 4 |  | eqidd | ⊢ ( 𝜑  →  ( 𝑥  ∈  𝑈 ,  𝑦  ∈  𝑈  ↦  ( ( Base ‘ 𝑦 )  ↑m  ( Base ‘ 𝑥 ) ) )  =  ( 𝑥  ∈  𝑈 ,  𝑦  ∈  𝑈  ↦  ( ( Base ‘ 𝑦 )  ↑m  ( Base ‘ 𝑥 ) ) ) ) | 
						
							| 5 |  | eqidd | ⊢ ( 𝜑  →  ( 𝑣  ∈  ( 𝑈  ×  𝑈 ) ,  𝑧  ∈  𝑈  ↦  ( 𝑔  ∈  ( ( Base ‘ 𝑧 )  ↑m  ( Base ‘ ( 2nd  ‘ 𝑣 ) ) ) ,  𝑓  ∈  ( ( Base ‘ ( 2nd  ‘ 𝑣 ) )  ↑m  ( Base ‘ ( 1st  ‘ 𝑣 ) ) )  ↦  ( 𝑔  ∘  𝑓 ) ) )  =  ( 𝑣  ∈  ( 𝑈  ×  𝑈 ) ,  𝑧  ∈  𝑈  ↦  ( 𝑔  ∈  ( ( Base ‘ 𝑧 )  ↑m  ( Base ‘ ( 2nd  ‘ 𝑣 ) ) ) ,  𝑓  ∈  ( ( Base ‘ ( 2nd  ‘ 𝑣 ) )  ↑m  ( Base ‘ ( 1st  ‘ 𝑣 ) ) )  ↦  ( 𝑔  ∘  𝑓 ) ) ) ) | 
						
							| 6 | 1 2 4 5 | estrcval | ⊢ ( 𝜑  →  𝐶  =  { 〈 ( Base ‘ ndx ) ,  𝑈 〉 ,  〈 ( Hom  ‘ ndx ) ,  ( 𝑥  ∈  𝑈 ,  𝑦  ∈  𝑈  ↦  ( ( Base ‘ 𝑦 )  ↑m  ( Base ‘ 𝑥 ) ) ) 〉 ,  〈 ( comp ‘ ndx ) ,  ( 𝑣  ∈  ( 𝑈  ×  𝑈 ) ,  𝑧  ∈  𝑈  ↦  ( 𝑔  ∈  ( ( Base ‘ 𝑧 )  ↑m  ( Base ‘ ( 2nd  ‘ 𝑣 ) ) ) ,  𝑓  ∈  ( ( Base ‘ ( 2nd  ‘ 𝑣 ) )  ↑m  ( Base ‘ ( 1st  ‘ 𝑣 ) ) )  ↦  ( 𝑔  ∘  𝑓 ) ) ) 〉 } ) | 
						
							| 7 |  | catstr | ⊢ { 〈 ( Base ‘ ndx ) ,  𝑈 〉 ,  〈 ( Hom  ‘ ndx ) ,  ( 𝑥  ∈  𝑈 ,  𝑦  ∈  𝑈  ↦  ( ( Base ‘ 𝑦 )  ↑m  ( Base ‘ 𝑥 ) ) ) 〉 ,  〈 ( comp ‘ ndx ) ,  ( 𝑣  ∈  ( 𝑈  ×  𝑈 ) ,  𝑧  ∈  𝑈  ↦  ( 𝑔  ∈  ( ( Base ‘ 𝑧 )  ↑m  ( Base ‘ ( 2nd  ‘ 𝑣 ) ) ) ,  𝑓  ∈  ( ( Base ‘ ( 2nd  ‘ 𝑣 ) )  ↑m  ( Base ‘ ( 1st  ‘ 𝑣 ) ) )  ↦  ( 𝑔  ∘  𝑓 ) ) ) 〉 }  Struct  〈 1 ,  ; 1 5 〉 | 
						
							| 8 |  | homid | ⊢ Hom   =  Slot  ( Hom  ‘ ndx ) | 
						
							| 9 |  | snsstp2 | ⊢ { 〈 ( Hom  ‘ ndx ) ,  ( 𝑥  ∈  𝑈 ,  𝑦  ∈  𝑈  ↦  ( ( Base ‘ 𝑦 )  ↑m  ( Base ‘ 𝑥 ) ) ) 〉 }  ⊆  { 〈 ( Base ‘ ndx ) ,  𝑈 〉 ,  〈 ( Hom  ‘ ndx ) ,  ( 𝑥  ∈  𝑈 ,  𝑦  ∈  𝑈  ↦  ( ( Base ‘ 𝑦 )  ↑m  ( Base ‘ 𝑥 ) ) ) 〉 ,  〈 ( comp ‘ ndx ) ,  ( 𝑣  ∈  ( 𝑈  ×  𝑈 ) ,  𝑧  ∈  𝑈  ↦  ( 𝑔  ∈  ( ( Base ‘ 𝑧 )  ↑m  ( Base ‘ ( 2nd  ‘ 𝑣 ) ) ) ,  𝑓  ∈  ( ( Base ‘ ( 2nd  ‘ 𝑣 ) )  ↑m  ( Base ‘ ( 1st  ‘ 𝑣 ) ) )  ↦  ( 𝑔  ∘  𝑓 ) ) ) 〉 } | 
						
							| 10 |  | mpoexga | ⊢ ( ( 𝑈  ∈  𝑉  ∧  𝑈  ∈  𝑉 )  →  ( 𝑥  ∈  𝑈 ,  𝑦  ∈  𝑈  ↦  ( ( Base ‘ 𝑦 )  ↑m  ( Base ‘ 𝑥 ) ) )  ∈  V ) | 
						
							| 11 | 2 2 10 | syl2anc | ⊢ ( 𝜑  →  ( 𝑥  ∈  𝑈 ,  𝑦  ∈  𝑈  ↦  ( ( Base ‘ 𝑦 )  ↑m  ( Base ‘ 𝑥 ) ) )  ∈  V ) | 
						
							| 12 | 6 7 8 9 11 3 | strfv3 | ⊢ ( 𝜑  →  𝐻  =  ( 𝑥  ∈  𝑈 ,  𝑦  ∈  𝑈  ↦  ( ( Base ‘ 𝑦 )  ↑m  ( Base ‘ 𝑥 ) ) ) ) |