Def b == if b false else true fi

is mentioned by

Thm* p:. p  p	[assert_of_bnot]
Thm* b:. b = false  b	[eqff_to_assert]
Thm* i,j:. ij = (j<i)	[bnot_of_le_int]
Thm* p,q:. (p  q) = (pq)	[bnot_thru_bor]
Thm* p,q:. (pq) = (p  q)	[bnot_thru_band]
Thm* p:. p = p	[bnot_bnot_elim]
Def ij == j<i	[le_int]
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