Some definitions of interest.
assert	Def b == if b True else False fi
	Thm* b:. b  Prop
eq_rat	Def a =q b == a.numb.den=b.numa.den
	Thm* x,y:. x =q y
qmul	Def a *q b == (a.numb.num)/(a.denb.den)
	Thm* p,q:. p *q q
rat	Def  ==
	Thm*   Type

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