> Assume r and s are in the hash table. To do (hcons r s) you
> look at the address of r and address of s, and make the hash
> code from this.
This is assuming that addresses are stable. I'd think that at least
some of the current CL implementations use relocating garbage
collectors.
> What is interesting about this is one can use the hash table
> idea to (for example) store all the simplified expressions,
> or all expressions with some property. Thus instead of
> tagging an expression with "simplified" or "factored" one
> can use a hash table.
Presumably the big win comes because you never have to resimplify the
same thing twice. Though you do have to worry about whether the
environment (global settings etc.) is the same....
-s