Some definitions of interest.
assert	Def b == if b True else False fi
	Thm* b:. b  Prop
eq_int	Def i=j == if i=j true ; false fi
	Thm* i,j:. (i=j)
rat	Def  ==
	Thm*   Type
nat_plus	Def  == {i:| 0<i }
	Thm*   Type
qdenom	Def q.den == 2of(q)
	Thm* q:. q.den
qnumer	Def q.num == 1of(q)
	Thm* q:. q.num

About: IF YOU CAN SEE THIS go to /sfa/Nuprl/Shared/Xindentation_hack_doc.html