| Step | Hyp | Ref | Expression | 
						
							| 1 |  | structfn.1 |  |-  F Struct <. M , N >. | 
						
							| 2 | 1 | structfun |  |-  Fun `' `' F | 
						
							| 3 |  | isstruct |  |-  ( F Struct <. M , N >. <-> ( ( M e. NN /\ N e. NN /\ M <_ N ) /\ Fun ( F \ { (/) } ) /\ dom F C_ ( M ... N ) ) ) | 
						
							| 4 | 1 3 | mpbi |  |-  ( ( M e. NN /\ N e. NN /\ M <_ N ) /\ Fun ( F \ { (/) } ) /\ dom F C_ ( M ... N ) ) | 
						
							| 5 | 4 | simp3i |  |-  dom F C_ ( M ... N ) | 
						
							| 6 | 4 | simp1i |  |-  ( M e. NN /\ N e. NN /\ M <_ N ) | 
						
							| 7 | 6 | simp1i |  |-  M e. NN | 
						
							| 8 |  | elnnuz |  |-  ( M e. NN <-> M e. ( ZZ>= ` 1 ) ) | 
						
							| 9 | 7 8 | mpbi |  |-  M e. ( ZZ>= ` 1 ) | 
						
							| 10 |  | fzss1 |  |-  ( M e. ( ZZ>= ` 1 ) -> ( M ... N ) C_ ( 1 ... N ) ) | 
						
							| 11 | 9 10 | ax-mp |  |-  ( M ... N ) C_ ( 1 ... N ) | 
						
							| 12 | 5 11 | sstri |  |-  dom F C_ ( 1 ... N ) | 
						
							| 13 | 2 12 | pm3.2i |  |-  ( Fun `' `' F /\ dom F C_ ( 1 ... N ) ) |