Re: Meaning of Numeric Type "digit"

Looking at the two sets of Brahmi numbers would also be instructive...

Sent from my Android phone
On Jul 12, 2012 6:21 AM, "Richard Wordingham" <
richard.wordingham_at_ntlworld.com> wrote:

> What is a number having a numeric type of "digit" meant to convey?
>
> The old Unicode 2.0 definition definition of "digit value" seemed clear:
> "Digit value. This is a numeric field. If the character represents a
> digit, not necessarily a decimal digit, the value is here. This covers
> digits which do not form decimal radix forms, such as the compatibility
> superscript digits. This field is informative."
>
> That definition seems to be gone. From what we now have, I can think
> of several meanings, e.g.:
>
> 1) It's a digit in a system of decimal place notation, but doesn't quite
> qualify for some reason. Typical examples are:
>
> a) U+19DA NEW TAI LUE THAM DIGIT ONE - cruelly denied "decimal" status
> because it wasn't assigned with 9 clones of the other Tai Lue digits.
>
> b) U+2070 SUPERSCRIPT ZERO - not in a contiguous range, and
> apparently possibility of misleading parsers
>
> c) U+2080 SUBSCRIPT ZERO - apparent possibility of misleading parsers
>
> 2) It's in a decimal system, but not with place notation:
>
> a) U+10E60 RUMI DIGIT ONE. By contrast U+10E69 RUMI NUMBER
> TEN is a mere "numeric" - possibly because numeric field values of
> blank for decimal digit value (field 6 in UnicodeData.txt), 1 as the
> digit value (field 7) and 10 as the value (field 8) would be too
> confusing, as well as contrary to the current rules.
>
> On the other hand, I don't see why, apart from a general disapproval of
> compatibility characters, the Roman numerals U+2170 SMALL ROMAN
> NUMERAL ONE to U+2178 SMALL ROMAN NUMERAL NINE don't count as digits.
>
> 3) It's derived from a decimal digit, e.g. U+2468 CIRCLED DIGIT
> NINE is "digit", whereas the next in the series, U+2469 CIRCLED NUMBER
> TEN, just has a numeric type of "numeric".
>
> ----
>
> It's not clear to me why the following decimal digits (in the normal,
> not the Unicode sense) are not classified as "digit" but just as numeric
>
> U+1D360 COUNTING ROD UNIT DIGIT ONE
> U+3021 HANGZHOU NUMERAL ONE
>
> The only reason for U+1D369 COUNTING ROD TENS DIGIT ONE not to be a
> digit that I can think of is that the system is conceived of as a
> centesimal system. The counting rods 'UNIT' and 'TENS' digits are used
> alternatively to avoid misreading, with various methods
> for indicating zero.
>
> Likewise, why are U+0C79 TELUGU FRACTION DIGIT ONE FOR ODD POWERS OF
> FOUR and related characters not digits? Is it because they are a base
> 4 (or collectively hexadecimal) system?
>
> Perhaps some light can be shed on the system by learning what people
> actually use the numeric types and (decimal) digit values for.
>
> Richard.
>
>
Received on Wed Jul 11 2012 - 20:41:18 CDT