[x3d-public] SFImage regex

Andreas Plesch andreasplesch at gmail.com
Sat Jun 9 10:43:04 PDT 2018


On Sat, Jun 9, 2018 at 1:19 PM, Don Brutzman <brutzman at nps.edu> wrote:
> good point... i've been grouping them just to keep the regexes a slight bit
> more readable, less possibility of error.  we could do cleanup of those
> (group) parentheses if it is preferable.

The parens do look more readable, at least to the casual regex reader.
Parens usually are used for capturing, eg. referencing the matched
group later although I am not sure if this is possible with XML
regexes which seem more basic. To regex regulars parens therefore may
cause human interpreters to look for those references. Also - at least
outside of XML - performance may be impacted from using a lot of
grouping.

Probably best to just leave the parens.

Tangentially, repeated ranges also look not so nice but are apparently
common: [0-9a-fA-F]
[0-9]|[a-f|[A-F] reads better to me and that is why I preferred that.
Not sure about any performance implications.

-Andreas

>
> On 6/9/2018 8:45 AM, Andreas Plesch wrote:
>>
>> On Sat, Jun 9, 2018 at 8:30 AM, Don Brutzman <brutzman at nps.edu> wrote:
>>>
>>> On 6/8/2018 3:13 PM, Don Brutzman wrote:
>>>>
>>>>
>>>>
>>>> *  These regexes all assume that leading/trailing whitespace has been
>>>> removed. It is possible to prepend/append regex constructs such as (\s)+
>>>> to
>>>> consume outer whitespace.
>>>
>>>
>>>
>>> correction: zero or more whitespace characters (\s)* rather than one or
>>> more
>>> whitespace characters (\s)+
>>
>>
>> Yes, but it is not necessary to group the \s class: \s*. I am not sure
>> if prepending/appending is preferable to using the collapse whitepace
>> XML restriction. Since there are more fluent regex than XML readers,
>> it may be.
>>
>> -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/brutzman
>



-- 
Andreas Plesch
Waltham, MA 02453



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