Def b == if b True else False fi

is mentioned by

Thm* A,B:Type, x:A+B. isl(x)  outr(x)  B	[outr_wf]
Thm* A,B:Type, x:A+B. isl(x)  outl(x)  A	[outl_wf]

In prior sections: bool 1

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