On Sat, 6 Feb 2021 at 13:46, Manfred Bergmann <manfred.bergm...@me.com> wrote: > Does anyone know what Peter Norvig had in mind when he said that metaclasses > can be used instead of Abstract Factory pattern?
Are you talking about slides 12 and 13? Peter does not mention metaclasses there or anywhere else in his slides. I believe his point is that make-instance is the factory. Classes are first-class values and make-instance accepts a class as its first argument. If you use qt-backend, gtk-backend, motif-backend classes, at some point you can make the decision about which class to instantiate and pass it to make-instance. He categorizes this pattern as invisible, which might explain why you're having trouble seeing it. :-) Cheers, Luís
