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Re: hash-tables

>I am having trouble with MCL's hash tables. Or at least I think the
>problem lies with MCL - perhaps it is my understanding of CL that is
>lacking. I am trying to retrieve objects that are uniquely identified via
>a tuple, rather than a single item for a key. CLtL2 states (with reference
>to hash tables): "Keys do not have to be symbols, they can be any Lisp
>object". I am using a list containing two values. Here are the details:

This is a known bug with MCL 2.0b1's equal & equalp hash tables. SXHASH
descends CLOS instances, whereas EQUAL & EQUALP do not. Hence if you
use a CLOS instance as a key (or part of a key) in an EQUAL or EQUALP
hash table, then change one of its slots or GC, it will likely hash to
a different place. This bug has been fixed for MCL 2.0 final.