How to ask "how big is it?"

[dla@diamond.s4cc.symbolics.com]

    Date: Tue, 8 Sep 87 09:16 EDT
    From: Scott Cyphers <Cyphers@YUKON.SCRC.Symbolics.COM>

    My assistant's technique has a problem with cdr-coded lists getting
    counted multiple times.  I would use 

    (SI:%FIND-STRUCTURE-HEADER (SI:FOLLOW-STRUCTURE-FORWARDING thing))

    on the objects you care about, using the returned header as the key into
    the hash table, and then sum %STRUCTURE-TOTAL-SIZE of the hash table
    elements. 

Of course, then you won't be counting the old copies of forwarded
structures which might be still hanging around taking up space.  All
this does is reinforce my original point that "how big is it?" is not a
simple question.