Re: Digit/letter variants in the "same" unified script (was: stability policy on numeric type = decimal)

From: karl williamson (
Date: Thu Jul 29 2010 - 18:13:26 CDT

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    Asmus Freytag wrote:
    > Having Nd be limited to characters that
    > a) are used in decimal radix numbers
    > b) are part of a complete, ordered sequence 0..9
    > would make this property regular enough to serve
    > implementers. You could script the creation of
    > relevant data for your implementation based on that
    > property.
    > *Exceptions* exist and need to be documented.
    > Having exceptions machine readable is not as
    > important, but having implementers understand
    > them is.
    > Therefore, the best thing is for these to become
    > something other than Nd, but to retain their numeric
    > type of digit.
    > Together with a detailed explanation of each in
    > the appropriate script chapter, AND a complete
    > summary of all exceptional cases in a central
    > place (section 4.6 comes to mind) would provide
    > implementers with the information they need.
    > The exceptional cases that I'm aware of are
    > a) Arabic using two complete series of digits
    > b) New Thai Lue using an extra digit 1
    > c) Han digits being scattered and used in two
    > different types of numeric expressions
    > d) ASCII digits being used for some scripts
    > as preferred decimal-radix digits, because
    > their native number system is not, or not
    > exclusively decimal-radix
    > The above information belongs in section 4.6
    > in summary form, or simply as table of pointers
    > to each script chapter that contains a description
    > of unusual numeric behavior for decimal-radix
    > digits.
    > (A separate table pulling together all the descriptions
    > of non-decimal radix number systems that are
    > discussed in the Standard would equally be useful
    > for the readers).
    > A./

    This sounds good to me.

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