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

Subject: Re: [boost] [Regex] Why doesn't this pattern match?
From: Sylvester-Bradley, Gareth (Gareth.Sylvester-Bradley_at_[hidden])
Date: 2009-12-08 06:10:48

>>  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".

If you want to match a '\' followed by an 'n' (as I think the OP needs),
do you need a regex of "\\\\n" (or "\\Q\\n\\E")?

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