is mentioned by

Def a *q b == (a.numb.num)/(a.denb.den)	[qmul]
Def a +q b == (a.numb.den+b.numa.den)/(a.denb.den)	[qadd]

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