Def p  q == if p true else q fi

is mentioned by

Thm* p,q:. (p  q)  p  q	[assert_of_bor]
Thm* u:. (u  true) = true	[bor_tt_simp]
Thm* u:. (u  false) = u	[bor_ff_simp]
Thm* p,q:. (p  q) = (pq)	[bnot_thru_bor]
Thm* p,q:. (pq) = (p  q)	[bnot_thru_band]
Def pq == p  q	[bimplies]
Def pq == (pq)  (pq)	[bxor]
Def p=q == (pq)  (pq)	[eq_bool]

Try larger context: StandardLIB IF YOU CAN SEE THIS go to /sfa/Nuprl/Shared/Xindentation_hack_doc.html