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Postings from April 2000
When a key-value pair is stored in a Perl hash, the hash value for the
key is stored with it. Then, when Perl is looking up a key, and finds
something in the bucket, it compares the hash values first, and only
compares the found key with the desired key if the hash values match.
This avoids many unnecessary string compares.
Folks on the mailing list for Dan Bernstein's CDB (constant database)
package are discussing how that works, and one of them mentioned:
Incidentally, I don't know if Dan invented this brilliant
idea. It doesn't seem to be in Knuth.
I said that this innovation is in Perl 1, and was probably not new
then. But I was surprised that it wasn't in Knuth---that suggests
that it is a more recent idea than one would have expected, perhaps
from the 1970s. Does anyone know when this was invented or by whom or
remember seeing this idea used in anything that predates Perl?
Mark-Jason Dominus mjd@plover.com
I am boycotting Amazon. See http://www.plover.com/~mjd/amazon.html for details.
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