Nuprl - Some Definitions

bool	`Def == Unit+Unit` `Thm* Type`
assert	`Def b == if b True else False fi` `Thm* b:. b Prop`
iff	`Def P Q == (P Q) & (P Q)` `Thm* (A B) Prop`
ifthenelse	`Def if b t else f fi == dec(b ; t; f)` `Thm* b:, A:Type, p,q:A. if b p else q fi A`
rev_implies	`Def P Q == Q P` `Thm* (A B) Prop`