Some definitions of interest.
assert	Def  b == if b True else False fi
	Thm*  b:. b  Prop
iff	Def  P  Q == (P  Q) & (P  Q)
	Thm*  A,B:Prop. (A  B)  Prop
is_discrete	Def  A Discrete == x,y:A. Dec(x = y)
	Thm*  A:Type. (A Discrete)  Prop

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