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Updated Hashing structure writ large (markdown)

Simon Brooke 2021-08-07 13:00:50 +01:00
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Hashing-structure-writ-large.md

@ -133,7 +133,7 @@ Is this a good hash function? Probably not. A hash function should ideally distr
Certainly in Clojure practice, keys in hash maps are almost always 'keywords', a particular variety of string-like-thing. Nevertheless, Clojure, like Common Lisp (and many, perhaps all, other lisps) allows, in principal, that any value can be used as a key in a hash map.
The hash outlined above of using 32 bits of previously unused space in the string payload works because there were 32 unused bits in the string payload. While a hash function with similar properties can be imagined for cons cells, there are not currently any unused bits in a cons payload. To add a hash value would require adding more bits to every cons space object.
The hack outlined above of using 32 bits of previously unused space in the string payload works because there were 32 unused bits in the string payload. While a hash function with similar properties can be imagined for cons cells, there are not currently any unused bits in a cons payload. To add a hash value would require adding more bits to every cons space object.
Our current cons space object is 256 bits: