Re: [Regex] \r matching \n

On 21/03/2026 15:31, Rainer Deyke via Boost wrote:
> On 3/20/26 20:33, John Maddock via Boost wrote:
>> On 20/03/2026 07:29, Olaf van der Spek via Boost wrote:
>>> Hi,
>>>
>>> In this regex the \n matches \r. How is this defined / controlled? Is
>>> there a way to only match \n?
>>>
>>>      std::string s = "[*] A\rB\n";
>>>      s = boost::regex_replace(s, boost::regex(R"(\[\*\](.+?)(\n|$))"),
>>> "<li>\\1</li>");
>>>      std::println("{}", js_encode(s)); // <li> A</li>\rB\n
>>
>> \n is a regular expression meaning "Match any newline character", 
>> which happens to include \r and a few other things as well.  If you 
>> want to match a literal '\n' then you need to escape it and the 
>> appropriate regular expression string is therefore R"\\n"
>
> He's trying to match the newline character, not '\' followed by 'n'. 
> Which in a raw string would be R"(
> )", with the actual line break in the raw string.
>
>
Yes exactly, the regular expression which matches a literal \n is \\n, 
otherwise \n on it's own is a regular expression operator and not a literal.

John.

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