Re: Hash table thread safety

>>>>> On Tue, 31 Mar 2026 12:15:18 +0100, Tim Bradshaw said:
> 
> The new one keeps a natural number which is the next index, and then two
> hash tables: k->o, and o->v (actually to a cons of key and value), where o
> is an index.  If you can increment the next index slot atomically (which you
> can in LW and SBCL) then you can know you have a unique (up to machine
> integers wrapping on SBCL) index for insertion.  The problems are (a)
> slower, and (b) if you delete lots of entries you end up with holes in the
> index space, so iteration can be slow.  You can get orphan o->kv entries but
> it can GC those if asked.

Can you replace the two hash tables with a single hash table mapping the key
to a cons of the index and the value?

-- 
Martin Simmons
LispWorks Ltd
http://www.lispworks.com/

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