[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
ASSOC and ASSQ on lists with atomic entries
- To: TLP at MIT-MC, ALAN at MIT-MC, RWK at MIT-MC, RMS at MIT-MC
- Subject: ASSOC and ASSQ on lists with atomic entries
- From: JONL at MIT-MC (Jon L White)
- Date: Tue ,20 Nov 79 10:51:00 EDT
CC: (BUG LISP) at MIT-MC, (BUG LISPM) at MIT-MC
1) as for maclisp, it appears to be a bug in the manual that this
isn't documented - the manual seems to imply that "association lists"
must contain only dotted pairs. The "feature" of maclisp's ASSQ
under which it really takes car of each item in the association
list must be considered a speed kludge in the same cattegory as that
of converting ATOM check for end of list in the various MAPs into
a NULL check in compiled code; one could construct pathological
cases which exploited/demonstrated this difference, but in fact in
the 5+ years that it has been installed, there has never been a
naturally-occurring complaing agains ASSQ/ASSOC. (on the other hand,
there have been a few complaints that compiled MAPs do not do the
same endtest check as the interpreted version, i.e. that NULL has
been substituted for ATOM).
2) the utility of being able to delete entries from an "association list"
by means of RPLACAing them to (), rather than having to re-invent
and/or open-code the mechanisms of DELETE, is supremely useful;
likely we should ensure that all of MACLISP/LISPM/NIL permit it.
3) some of us will receive multiple copies of this note, due to the
mail-forwarding process - should we perhaps define a new mailing
list which reaches BUG-LISP, BUG-LISPM, and NIL mailing lists?