[ddj] Dynamic backreferences?

[Patrick Maynard]

Thanks!

(As I said, I realize that doing it entirely in regular expressions is a
bit of a curiosity case, rather than the best way to do it. Was just ...
curious.)


On Wed, Sep 25, 2013 at 7:50 PM, Tarek Amr <tarekamr at gmail.com> wrote:

> Hi,
>
> Here is a python code that should do what you want
>
> def colrepeat(text):
> ...     instr =  text.string[text.start()+1:text.end()-1]
> ...     outstr = '<'
> ...     for col in instr.split(','):
> ...             outstr = outstr + ','.join([col] * 3) + ','
> ...     outstr += '>'
> ...     return outstr
> ...
> re.sub('\<[a-z\,]+\>', colrepeat, 'I like <red,green,blue> and
> <white,black>')
>
>
>
>
> On Wed, Sep 25, 2013 at 9:15 PM, Patrick Maynard <
> patrickmaynard.bs at gmail.com> wrote:
>
>> Is there a simple way to make a regular expression generate its own back
>> references?
>>
>> For example, if I have strings "this is a <red,blue,green> set" and "this
>> is a <red,brown,blue,green,brown> string" (and several other strings that
>> vary in the number of color instances), and I know that the brackets will
>> always be exclusively wrapped around the comma-delimited color list, can I
>> write a single replacement pattern that will repeat each color three times
>> before going to the next color?
>>
>> I realize that there are a ton of much better, non-big-hammer ways of
>> doing this. I'm just curious about this as a sort of academic exercise at
>> this point. Is there a way to accomplish this strictly with regex?
>>
>> -- Patrick
>>
>>
>>
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>>
>
>
> --
> Best Regards
> Tarek Amr
>
> http://tarekamr.appspot.com/
>
>
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