Some definitions of interest.
int_iseg	Def {i...j} == {k:| ik & kj }
	Thm* i,j:. {i...j}  Type
lt_int	Def i<j == if i<j true ; false fi
	Thm* i,j:. (i<j)
nat	Def  == {i:| 0i }
	Thm*   Type
not	Def A == A  False
	Thm* A:Prop. (A)  Prop
sq_type	Def SQType(T) == x,y:T. x = y  {x ~ y}
top	Def Top == Void(given Void)
	Thm* Top  Type

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