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