reduce should allow an accessor function to be specified

[David C. Plummer <DCP@quabbin.scrc.symbolics.com>]

    Date: Sat, 14 Nov 87 04:38:32 est
    From: Mark Bromley <bromley@Think.COM>

    ...
    It would be much more natural to be able to use the following

    (reduce #'+ sequence :key #'car).

Several people have suggested this functionality and I think most of us
think it is reasonable.  Many people also believe the :KEY is not the
right keyword for extraction on the grounds that keys are for
predicates, not for operators.  We even had a naming contest for the
name of extraction keyword.  I don't remember if there was a clear
winner.

I really don't know what to do with this conversation.  We've been over
this about 5 times now and it seems like beating a dead horse to have
another long discussion.  On the other hand, we never reached
consensus/conclusion during any of those previous attempts, so this
issue will come up again and again until the functionality exists.