23 lines
928 B
Plaintext
23 lines
928 B
Plaintext
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ISBN (books) and ISSN (serials)
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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This directory contains definitions for a couple of PostgreSQL
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external types, for a couple of international-standard namespaces:
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ISBN (books) and ISSN (serials). Rather than just using a char()
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member of the appropriate length, I wanted my database to include
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the validity-checking that both these numbering systems were designed
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to encompass. A little bit of research revealed the formulae
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for computing the check digits, and I also included some validity
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constraints on the number of hyphens.
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The internal representation of these types is intended to be
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compatible with `char16', in the (perhaps vain) hope that
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this will make it possible to create indices of these types
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using char16_ops.
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These are based on Tom Ivar Helbekkmo's IP address type definition,
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from which I have copied the entire form of the implementation.
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Garrett A. Wollman, August 1998
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