[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Hash tables => Hashing functions
- To: Wholey at CMU-20C, Common-Lisp at SU-AI
- Subject: Hash tables => Hashing functions
- From: Daniel L. Weinreb <dlw at SCRC-TENEX at MIT-MC>
- Date: Fri, 08 Oct 1982 21:54:00 -0000
- In-reply-to: The message of 8 Oct 82 14:00-EDT from Skef Wholey <Wholey at CMU-20C>
No, because it is very hard/expensive to provide a function that hashes
on EQ (and EQL) in a Lisp with a copying GC. That's why we provide hash
tables: the system can deal with this but the user can't. For example,
Lisp Machine hash tables all include a little variable that gets compared
against a global how-many-flips-have-happened counter, and if there has
been a flip since last time, the hash table has to be completely rehashed.
The user should not see this counter, especially not as part of the C.L.