|   | Some definitions of interest. | 
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| injection_type | Def  A inj  B == {f:(A  B)| Inj(A; B; f) } | 
 | |   | Thm*   A,B:Type. A inj  B   Type | 
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| int_seg | Def  {i..j } == {k: | i   k < j } | 
 | |   | Thm*   m,n: . {m..n }   Type | 
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| nat_plus | Def     == {i: | 0<i } | 
 | |   | Thm*       Type | 
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| not | Def   A == A    False | 
 | |   | Thm*   A:Prop. ( A)   Prop |