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Property lists

    Date: 17 May 1985 0128-PDT
    From: Rem@IMSSS

    It seems to me that the choice of whether property lists should be kept
    as ASSOC lists or as alternating lists should be an implementation issue.
    Functions for adding, deleting, finding, modifying them should exist
    so that the user hardly ever needs to actually see the structure except
    when debugging. Yet the CL manual insists that in CL they must be implemented
    as alternating lists, not as ASSOC lists. Why was this decision made??
    Should it be rescinded?


For one thing, the term "property list format" provides useful terminology
for contrasting "association list format".

For another thing, GETF has a variety of uses in situations where lists were
not actually created by (SETF (GETF ...)), etc. eg, keyword argument lists can
be easily manipulated using GETF. You couldn't do that if the format wasn't
defined. Instead, you'd write code identical to what's there just so that you
could use it "safely". Since there are advantages to saying what the format is
and no particular disadvantages (data abstractions notwithstanding; you could
always write a TABLE abstraction), it has been the concensus that the format
might as well be documented.