[x3d-public] X3D Regex

[Andreas Plesch]

Hi Don

On Thu, Jun 7, 2018, 12:17 AM Don Brutzman <brutzman at nps.edu> wrote:

> great to see the dialog and scrutiny, thanks!
>
> intent is to allow legal/standard content but disallow (or at least
> diagnose) broken/problematic/nonstandard content.
>

I think it may be helpful to more definitely state what the function of the
regex is:

- flag certainly broken content but still allow questionable content
- only allow well behaved content and flag questionable but parseable and
possibly legal content

There could be two versions, strict and lax.


> for MFInt32,
>
> - legal: 0 1 2 30 -0 -1 -2 -30
>
> - illegal: 010 -020 (leading zeroes also an indicator that intermediate
> whitespace was dropped)
>

The official regex /((\+|\-)?(0|[1-9][0-9]*)?( )?(,)?( )?)*/  currently
allows leading zeros as legal, perhaps by accident.


> - single comma OK between numbers, but multiple commas an indicator that
> an intermediate number was dropped
>

The official regex currently allows multiple commas.

Other patterns to clarify as being considered problematic include:

- +0
- -0
- + 12 (white space after sign)
- tab,newline,return as white space
- capital letters for hex: 0xAF
- 0X in addition to 0x as prefix for hexadecimal


> I have the O'Reilly books on this topic, they often give good/adaptable
> "cookbook recipes" worth considering.  can look further next week.
>
> it is helpful to be very wary of any conclusions whatsoever without
> testing a regex.
>

Oh yes.


>
> if alternatives are found, great - we can test with online tools, with
> Netbeans/X3D-Edit, and with regression testing of the X3D Examples Archive.
>

It sounds like the current regex does not quite match expectations.
The archive may not have leading zeros anywhere ? Or some of the other
problematic patterns like multiple commas ?

-Andreas


> 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/brutzma
> n
>
>
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