[Boost-users] Pattern issue with boost::regex

Subject: [Boost-users] Pattern issue with boost::regex
From: Tal Shnaiderman (STAL_at_[hidden])
Date: 2014-10-23 04:12:23

Hi All,

I have a question regarding boost::regex pattern recognition and groups

I created the following code, in it i created a pattern and a string to 
match:

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p = "((a b (f+\\.))d d(\\3))";
str="a b ffff.d dfff.";

boost::regex pattern(p,  boost::regex::icase&boost::regex::extended 
&~boost::regex::no_bk_refs);
bool match = boost::regex_match(str, pattern);
cout << str << ((match)?"-Pattern is legal":"-Pattern is illegal" )<< 
endl;

Pattern is illegal

I'm saw that my result is 'Pattern is illegal' because the group \\3 that 
refers to (f+\\.) isn't equal to it. if I change the input to 
 
str="a b ffff.d dffff.";

The pattern is legal.

In other words my original plan was to use the \\3 instead of writing the 
pattern;

 
p = "((a b (f+\\.))d d(f+\\.))";

But I can see that in the original pattern it simply expect the same 
output to reappear

Is there a way I can use the group naming not to copy the (f+\\.) group?

Thanks, I hope my Q is clear since I'm new to the regex topic.