Re: [boost] [Regex] Why doesn't this pattern match?

Subject: Re: [boost] [Regex] Why doesn't this pattern match?
From: John Maddock (john_at_[hidden])
Date: 2009-12-08 05:51:42

>  Yes, Robert, You are right. I am trying to change \\n (wchar_t  '\' and 
> wchar_t 'n') with a real new line symbols and it doesn't work. Allthought, 
> then I am trying to find only wchar_t 'n' (or any other letter) everything 
> is working good. The problem is that I have XML configuration file 
> (Unicode), where all new lines are L"\\n" (!!! not '\n' !!!). I can't 
> change that file format. Of course I can program that replace without 
> boost::regex, but I am afraid that I'll loose my sleep afterwards...
>
>>> You're replacing each occurrence of \\n with \\n, so the
>>> string at the end should be exactly the same! :-)
>
>> The replacement is "\n" not "\\n" so the '\' followed by 'n' in str 
>> should be replaced with a newline, right?

No.  Remember the compiler gets first bite at the escape characters, so if 
you put a string "\\n" in your program, that gets passed to Boost.Regex as 
the two character string: "\n", which matches a single newline character. 
If you want to match a \ followed by a \n then you need a regex of "\\\n".

HTH, John.