Re: Origin of the U+nnnn notation

From: Guy Steele (Guy.Steele@Sun.COM)
Date: Wed Nov 09 2005 - 10:43:33 CST

  • Next message: Philippe Verdy: "Re: U+nnnn notation and normative identifiers."

    On Nov 8, 2005, at 10:52 PM, Philippe Verdy wrote:

    > From: "Guy Steele" <Guy.Steele@sun.com>
    >
    >>> A positive value too. Zero is both negative and positive.
    >>>
    >>>
    >> That is not the mathematically conventional use of those terms;
    >> rather, zero is neither negative nor positive. That is why we use
    >> the
    >> terms nonnegative (to mean "zero or positive") and nonpositive
    >> (to mean "zero or negative").
    >>
    >
    > That's the conventional mathematical use of the term positive, as I
    > learnt it. To say not null, I learnt "strictly positive", and never
    > "non-negative". This may be cultural differences here (I'm in
    > France, the terms were actually in French). But there are much
    > enough mathematical demonstrationsand definitions of variables that
    > use "positive" inclusively. We could also say "positive or null"
    > but this is generally not necessary.
    >

    > Okay, fair enough. (I am no expert in French, but of course
    I respect the work and usage of French mathematicians.
    I consulted a standard English dictionary, Merriam-Webster's
    Tenth Collegiate, before making my remark, and the
    Mathematical Dictionary by James and James agrees,
    so I stand by my remarks about the technical meanings of
    the terms in English. I refrain from citing the Wikipedia!)

    ObUnicode: At http://www.unicode.org/Public/UNIDATA/UCD.html
    we read the description of field 8 in UnicodeData.txt:

        (8) If the character has the numeric property, as specified in
    Chapter 4
        of the Unicode Standard, the value of that character is
    represented with
        an positive or negative integer or rational number in this field.

    [Yes, "an" positive, sic.] The author of this text seems to assume that
    "positive or negative" includes zero, inasmuch as U+0030, for example,
    has the value 0 in field 8. (I would have written "with a (possibly
    signed)
    integer or rational number" and then given the three examples of
    U+0035 DIGIT FIVE having value 5, U+1946 LIMBU DIGIT ZERO having
    value 0, and U+0F33 TIBETAN DIGIT HALF ZERO having value -1/2.)

    --Guy Steele

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