Some definitions of interest.
assert	Def b == if b True else False fi
	Thm* b:. b  Prop
hlt	Def lt == m:. n:. m<n
	Thm* lt  (hnum  hnum  hbool)
hsuc	Def suc == n:. n+1
	Thm* suc  (hnum  hnum)

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