Keyed multiplication

Can I propose a simply-phrased question?

I have an IntArray in @P1 and a NumArray in @P2. How would I do the
equivalent of:

S1 = P1[5] * P2[5]

I'm not asking about how to do it currently, but rather how it should be
done in the 'final keyed interface'. When explaining, I'd appreciate
sample pasm code and/or rough pseudo-code for the unimplemented ops and
methods you're using. Also, it prevents any magical hand-waving. :)

Beware, as I believe this is a very tricky question that will delve into
areas of mm-dispatch. However, if answered, I think it will give great
insights into "the way things (should) work".

Of course, the possibility exists that I am completely missing something,
and this truly is a simple question. :)

Thanks,
Mike Lambert

• Keyed multiplication by Mike Lambert