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developerWorks: Inversion Lists with Perl

Oct 27, 2003, 06:00 (0 Talkback[s])
(Other stories by Teodor Zlatanov)

"I first learned about inversion lists in relation to Perl 6 Unicode programming. In Unicode programming, inversion lists are essential for storing binary properties of character ranges. Dr. Mark Davis, the president of the Unicode consortium, was kind enough to point me to some C implementations of inversion lists. He said (paraphrased):

'I first started using inversion lists in about 1985. They are compact for most data, have fast lookup, and allow fast boolean operations. I don't know of any pre-existing implementations, but it is simple enough that it could well have been developed multiple times.'

"In addition, Richard Gillam's book 'Unicode Demystified' contained helpful information about inversion lists, in addition to many other fascinating topics. I recommend it highly for anyone interested in Unicode programming..."

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