Def filter(P;l) == reduce(a,v. if P(a) [a / v] else v fi;nil;l)

is mentioned by

Def f  g == <1of(f) @ filter(a.a  dom(f);1of(g)),a.f(a)?g(a)>

[fpf-join]

In prior sections: mb list 1 mb list 2 mb event system 1 mb event system 3

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