[x3d-public] X3D regular expression (regex) improvements

[Don Brutzman]

Thanks for noticing the \ omission on the negative lookahead examples - now fixed.  The other uses of . in regex patterns were all escaped as \. correctly.


On 8/17/2018 1:36 PM, Leonard Daly wrote:
> Just a single note and a question.
> 
> [most of message stripped away...]
> 
> 
>> It is great when we find those patterns, am trying to keep things maintainable.  The color-coding on web page definitely helps.
>>
>> Negative lookahead is good for avoiding illegal values, but not allowed in XML Schema (probably to avoid computational denial of service attacks_.  Have listed a pattern nevertheless, other languages/tools might want to use it.
>>
>> ==================
>> Disallowed values:
>>
>> * Negative lookahead filters can disqualify attributes that contain illegal values.
>> * W3C Recommendation for XML Schema (XSD) unfortunately does not support this construct.
>> * (?!((0|0.0*|.0+)\s+){3}) prohibits 0 0 0 since zero vector is illegal as initial axis triplet of an SFRotation.
> 
> As I read the above
> 
> If not
>    (0 or 0.0* or .0+
>     repeated white-space character
>    ) three times
> 
> You should escape the "dot"s; otherwise, it accepts any character (the dots are meta-character when not in a character class)
> 
> This would be:
> 
>     (?!((0|0\.0*|\.0+)\s+){3})
> 
> 
> See https://regex101.com/ to test and explain the regex.
> 
> 
> Is there any consideration for internationalization of number display. Most of Europe uses "," (comma) as the radix character (decimal separator). [See https://docs.oracle.com/cd/E19455-01/806-0169/overview-9/index.html]
> 
> 
> 
> -- 
> *Leonard Daly*
> 3D Systems & Cloud Consultant
> LA ACM SIGGRAPH Past Chair
> President, Daly Realism - /Creating the Future/
> 
> 
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all the best, Don
-- 
Don Brutzman  Naval Postgraduate School, Code USW/Br       brutzman at nps.edu
Watkins 270,  MOVES Institute, Monterey CA 93943-5000 USA   +1.831.656.2149
X3D graphics, virtual worlds, navy robotics http://faculty.nps.edu/brutzman