Re: [boost] [regex] number of back references

From: Eric Niebler (eric_at_[hidden])
Date: 2007-04-26 12:29:36

John Maddock wrote:
> Lorenzo Bettini wrote:
>> Hi
>>
>> is there any plan to support more than 9 back references in the regex
>> library?
> 
> You can have as many marked sub-expressions as you want, and refer to them 
> in the match_results structure once you have a match.  What you can't do at 
> present is have a true back-reference say \12 in your expression.  This is 
> basically a problem with the regex syntax, so if you know of a good syntax 
> extension that's already in use then it would trivial to support this.

You could use xpressive, which handles this case. Any \ddd where d is a 
decimal digit is interpreted as a back-reference if

- The backreference number is less than 10
-OR-
- The backreference number is less than or equal to the number of 
capturing groups seen so far.

I believe that's perl's rule.

-- 
Eric Niebler
Boost Consulting
www.boost-consulting.com