
When should I use a hash table instead of an association list? - pravj
http://www.faqs.org/faqs/lisp-faq/part2/section-2.html
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ketralnis
> Alists can sometimes be more efficient if the keys are sorted according to
> frequency, with the most heavily accessed keys appearing at the front of the
> list

You can also get this with splay trees, and then you get some of your other
nice tree behaviours like faster inserts, immutability potential, etc

