Re: Reasonable to propose stability policy on numeric type = decimal

From: karl williamson (public@khwilliamson.com)
Date: Sun Jul 25 2010 - 17:00:14 CDT

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    CE Whitehead wrote:
    >
    >
    > Sorry for my last email; I have that signature in hotmail and always
    > delete it but do have it for a few private emails; but sorry as I ment
    > to delete it but was very very tired.
    >
    > --C. E. Whitehead
    > cewcathar@hotmail.com <mailto:cewcathar@hotmail.com>
    > ------------------------------------------------------------------------
    > From: cewcathar@hotmail.com
    > To: public@khwilliamson.com; verdy_p@wanadoo.fr
    > CC: kent.karlsson14@telia.com; unicode@unicode.org
    > Subject: RE: Reasonable to propose stability policy on numeric type =
    > decimal
    > Date: Sun, 25 Jul 2010 16:24:01 -0400
    >
    >
    > > . . .
    > > Date: Sun, 25 Jul 2010 10:43:11 -0600
    > > From: public@khwilliamson.com
    > > To: verdy_p@wanadoo.fr
    > > CC: kent.karlsson14@telia.com; unicode@unicode.org
    > > Subject: Re: Reasonable to propose stability policy on numeric type =
    > decimal
    > >
    > > Philippe Verdy wrote:
    > > > "Kent Karlsson" <kent.karlsson14@telia.com> wrote:
    > > >> Den 2010-07-25 03.09, skrev "Michael Everson" <everson@evertype.com>:
    > > >>> On 25 Jul 2010, at 02:02, Bill Poser wrote:
    > > >>>> As I said, it isn't a huge issue, but scattering the digits
    > makes the
    > > >>>> programming a bit more complex and error-prone and the programs
    > a little less
    > > >>>> efficient.
    > > >>> But it would still *work*. So my hyperbole was not outrageous.
    > And nobody has
    > > >>> actually scattered them. THough there are various types of "runs"
    > in existing
    > > >>> encoded digits and numbers.
    > > >> While not formally of general category Nd (they are "No"), the
    > superscript
    > > >> digits are a bit scattered:
    > > >>
    > > >> 00B2;SUPERSCRIPT TWO
    > > >> 00B3;SUPERSCRIPT THREE
    > > >> 00B9;SUPERSCRIPT ONE
    > > >> 2070;SUPERSCRIPT ZERO
    > > >> 2074;SUPERSCRIPT FOUR
    > > >> ...
    > > >> 2079;SUPERSCRIPT NINE
    > > >>
    > > >> And there are situations where one wants to interpret them as in a
    > > >> decimal-position system.
    > > >
    > > > Scattering does not only affect decimal digits, but also mathematical
    > > > operators needed to represent:
    > > >
    > > > - the numeric sign (« - » or « + »), with at least two variants for
    > > > the same system to represent the minus sign (either the ambiguous
    > > > minus-heighten, the only one supported in many text-to-number
    > > > conversions, or the true mathematical minus sign U+2212 « − » that has
    > > > the same width as the plus sign), including some « alternating signs »
    > > > that exist in two opposite versions (« ± », « ∓ »);
    > > >
    > > > - the characters that represent the decimal separator (« . » or « , »)
    > > > which is almost always needed but locale-specific (this is not just a
    > > > property of the script);
    > > >
    > > > - the optional character used to note exponential notations and used
    > > > in text-to-number conversion (usually « e » or « E »);
    > > >
    > > > - the optional characters used in the conventional formatting for
    > > > grouping digits (NNBSP alias « fine », with possible automatic
    > > > fallback to THINSP in font renderers and in rich-text documents
    > > > controlling the breaking property with separate style, or fallback to
    > > > NBSP in plain-text documents, or fallback to standard SPACE in
    > > > preformatted plain-text documents, « , », or « ' », and possibly other
    > > > punctuations in their « wide » form, for ideographic scripts).
    > > >
    > > > Some of them exist in exponential/superscript or indice/subscript
    > > > versions (notably digits and decimal separators), but not all of them
    > > > (not all separators for grouping digits, using NNBSP may not be
    > > > appropriate as its width is not adjusted and it does not have the
    > > > semantic of a superscript or subscript).
    > > >
    > > > For generality, it seems better to assume that digits and other
    > > > characters needed to note numbers in the positional decimal system may
    > > > be scattered (libraries may still avoid the small overhead of
    > > > performing table lookups, by just inspecting a property of the
    > > > character '0' or of the convention use, that will either say that it
    > > > starts a contiguous ranges, or that the complete sequence is stored in
    > > > a lookup array for the 10 digits.
    > > >
    > > > The general category "Nd" may not always be accurate to find all
    > > > digits usable in decimal notations of integers, because the sequence
    > > > may have been incomplete when it was first encoded, and completed
    > > > later in scattered positions.
    > > >
    > > > In this case, the digits will often have a general property of "No"
    > > > (or even "Nl") that will remain stable. What should also be stable is
    > > > their numeric value property (but I'm not sure that this is the case
    > > > of "Nl" digits, notably for scripts systems using letters in a way
    > > > similar to Greek or Hebrew letters as digits, even if Greek and Hebrew
    > > > digits are not encoded separately from the letters that these number
    > > > notations are borrowing).
    > > >
    > > > Also I'm not sure that scripts that define "half-digits", or digits
    > > > with higher numeric values than 9, are permitting the use of their
    > > > digits with a numeric value between 0 and 9, in a positional decimal
    > > > system. The Roman numeric system is such a numeric system (borrowing
    > > > some scattered Latin letters and adding a few other specific digits)
    > > > where this will be completely wrong.
    > > >
    > > > Or another base than 10 could be assumed by their positional system,
    > > > even if their digits are encoded in a contiguous range of characters
    > > > for the subset of values 0 to 9. This is probably no longer the case
    > > > with scripts that have modern use, but in historical scripts or in
    > > > historical texts using a modern script, the implied base may be
    > > > different and would have used more or less distinct digits. So instead
    > > > of guessing automatically from the encoded text, it may be preferable
    > > > to annotate the text (easy to insert if the conversion of the
    > > > historical text uses some rich-text format) to specify how to
    > > > interpret the numeric value of the original number.
    > > >
    > > > And sometimes, the conversion to superscripts/subscripts compatibility
    > > > characters will not be possible even if some of them may be converted
    > > > safely to their numeric value, after detecting that they are in
    > > > superscript/subscript and that they don't behave the same as normal
    > > > digits (16²⁰ must NOT be interpreted as the numeric value 1620, but
    > > > must be parsed as two successive numbers 16 and 20, where the second
    > > > one has the semantic of an exponent, as if there was an exponentiation
    > > > operator between the two numbers).
    > > >
    > > > It is also very frequent that only a few superscript digits will be
    > > > supported in one font, and other digits may be borrowed from another
    > > > font using a completely distinct style with distinct metrics or may
    > > > not be displayed at all (missing glyph). The result is then horrible
    > > > if you can't predict which font will be used that support the 10
    > > > digits in a contiguous range of values (even if they are scattered in
    > > > the code space).
    > > >
    > This does seem relevant to me.
    > > > When converting numbers to text with exponential notations, the use of
    > > > superscripts should only be used with care, knowing that this won't be
    > > > possible in all scripts, and that only integers without grouping
    > > > separators can be used.
    > > >
    > > > Some writing systems (unified as « scripts » in Unicode) will still
    > require to:
    > > >
    > > > - either use rich-text styling for superscripts used in the
    > > > conventional notation of exponents,
    > > >
    > > > - or use an explicit exponentiation operator, such as the ASCII symbol
    > > > U+005E "^" (which is not the same as a modifier letter circonflex
    > > > U+02C6 "ˆ", and that many fonts render at with glyph size and position
    > > > different from the the combining diacritic and implied by the modifier
    > > > letter), or a mathemetical operator or modifier letter (like the
    > > > upward arrow head U+02C4 "˄" that some fonts render as the
    > > > mathematical wedge operator on the baseline U+2227 "∧", or the less
    > > > ambiguous upward arrow U+2191 "↑").
    > > >
    > > > Philippe.
    > > >
    > > >
    > > >
    > > That all may be true, but it is really besides the point.
    > >
    > > I'm considering extending an existing computer programming language
    > > which currently only understands numbers composed solely by the ASCII
    > > numbers to also understand those from other scripts. I'm not going to
    > > do it unless it is easy within the existing implementation (not some
    > > theoretical better implementation) and efficient and not a security
    > threat.
    > >
    > > The symbols for operators like exponentiation are already set in stone.,
    > > and their being scattered isn't relevant. Likewise, non-decimal-digit
    > > numbers, like subscripts, are also not relevant.
    > >
    > > I found a way to do the implementation that meets all my criteria, but
    > > is based on the existing pattern of Gc=Nd (or Nt=De) code point
    > > assignments. The assignments have so far been prudent, to use Asmus'
    > > term. I was merely trying to see if this prudence could be codified so
    > > that my implementation wouldn't get obsoleted on a whim in some future
    > > Unicode release.
    > >
    > > I hadn't thought of the case where a zero is later found or its usage
    > > develops in a script, and suddenly all the digits in that script change
    > > from Nt=Di to Nt=De, which because of an existing stability policy would
    > > necessarily require their general category changing to Nd.
    > >
    > > Prudence would dictate, then, that when assigning code points to the
    > > numbers in a script, that a contiguous block of 12-13 be reserved for
    > > them, such that the first one in the block be set aside for ZERO; the
    > > next for ONE, etc.
    > >
    > > My original question comes down to then, would it be reasonable to
    > > codify this prudence? People have said it will never happen. But no
    > > one has said why that is.
    > >
    > > Obviously, things can happen that will mess this up--the Phaistos disk
    > > could turn out to be a base-46 numbering system, as an extremely
    > > unlikely example. But by dictating prudence now, most such eventualities
    > > wouldn't happen.
    > >
    > > I have since looked at the Nt=Di characters. The ones that aren't in
    > > contiguous runs are the superscripts and ones that would never be
    > > considered to be decimal digits, such as a circled ZERO.
    > Hi
    > Are you proposing that superscripts be in contiguous runs or not?

    I was not proposing that. Just the codification of what existing
    practice has been for Numeric_Type=Decimal_Digit. Superscripts are of
    Numeric_Type=Digit; the two names are too similar, and cause confusion.

    I know of no general purpose programming language that figures out math
    equations with superscripts. If you want exponentiation, you have to
    specify an exponentiation operator.

      Above
    > you disallowed subscripts (although
    > I think mathematically subscripts have some meaning in equations as do
    > superscripts and it might worth converting them albeit separately from
    > other numbers; if these were converted it would allow complete equations
    > to be converted from character strings -- but with only digits 1-9 I do
    > not see that much of an issue; I'd personally like to find a subscript
    > i; but so far I've just looked at:
    > http://unicode.org/charts/PDF/U2070.pdf where the subscripts 0-9 are all
    > contiguous but the superscript 1, 2, and 3 are not; searching through
    > http://unicode.org/Public/UNIDATA/UnicodeData.txt that was all I found;
    > I then started going through code charts one by one and so far have
    > gotten as far as Old South Arabian and have not found superscript i or
    > more superscript decimal numbers though maybe I've missed something --
    > the Arabic sukun is not going to be part of a series of superscripts in
    > any case).
    >
    > > The only run
    > > in the BMP which doesn't have a zero is Ethiopic. It seems extremely
    > > unlikely to me that a zero will be discovered or come into use with that
    > > script. I'm guessing that they have adopted European numbers in order
    > > to have commerce with the rest of the world.
    > >
    > > There are several runs in the SMP, but the code point where a zero would
    > > go isn't assigned.
    > >
    > > I don't know for sure, but it appears to me that we are running out of
    > > non-dead scripts to encode. I see that draft 6.0 has only 544 BMP code
    > > points not in any block and not much in the pipeline. I would think
    > > that most any script yet to be encoded would have borrowed numbering
    > > systems from their neighbors.
    > >
    > > And there is still plenty of space in the SMP, so this proposal to
    > > require prudence should not use up too many precious unassigned code
    > points.
    > >
    > If it does not take up too much space; I support this proposal although
    > there is no way that characters are contiguous in any case -- so for
    > doing sorts and such this is not going to help really normally.
    >
    > Best,
    >
    > C. E. Whitehead
    > cewcathar@hotmail.com <mailto:cewcathar@hotmail.com>
    >



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