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Hash Table Type

A hash table is a very fast kind of lookup table, somewhat like an alist in that it maps keys to corresponding values, but much faster. The printed representation of a hash table specifies its properties and contents, like this:

(make-hash-table)
     ⇒ #s(hash-table size 65 test eql rehash-size 1.5
                             rehash-threshold 0.8125 data ())

See Hash Tables, for more information about hash tables.