From: karl williamson (firstname.lastname@example.org)
Date: Mon Apr 12 2010 - 12:09:00 CDT
Shriramana Sharma wrote:
> On 2010-Apr-05 01:58, karl williamson wrote:
>> Tamil's digits are not positional according to Richard Gillam. They
>> have General category of Nd. Could this be used to cause a naive program
>> to calculate an incorrect value of an input number, such that mention of
>> this possibility would be warranted in TR36?
> Have you read: http://www.unicode.org/notes/tn21/ ? It is hinted (though
> not perhaps very explicitly said) that today the positional system is
> indeed used. Therefore I (a native Tamil speaker and writer) do not
> think that today we would expect applications to *commonly* support the
> old numeral system.
> In any case, non-positional evaluation of numbers should only be
> performed by an application if it encounters the characters ௰ ௱ and ௲. A
> number which does not use these characters can safely be processed as
> positional. A number which uses them, on the other hand, will have to be
> checked for being properly formatted, i.e. properly composed, since in
> the non-positional system digits like ௧ ௨ etc would never be seen
> adjacent to each other without being punctuated by one of the three
> characters ௰ ௱ and ௲. Therefore any number containing one of ௰ ௱ and ௲
> but also containing any two normal digits ௧ ௨ etc adjacent to each other
> is badly formatted and hence has no (defined) value.
> Therefore there is a clear distinction between the two systems, and
> while the same numerical value can be represented by two different
> strings of characters, one for each system, the same string cannot
> represent two different numbers. These systems are self-exclusive. I
> mean to say that they both naturally exclude the simultaneous use of the
> other system in the same number. Therefore I think that there is little
> scope for security problems here.
Thanks for your response.
Can anyone tell me: Are there other scripts where Gc=Nd characters can
behave with other than the positional meanings of the digits 0-9? The
only technical note that has "number" in the title is the one that
Shriramana mentioned, so I'm assuming not.
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