C++ regex escaping punctional characters like "."

Question

Matching a "." in a string with the std::tr1::regex class makes me use a weird workaround.

Why do I need to check for "\\\\." instead of "\\."?

regex(".") // Matches everything (but "\n") as expected.
regex("\\.") // Matches everything (but "\n").
regex("\\\\.") // Matches only ".".

Can someone explain me why? It's really bothering me since I had my code written using boost::regex classes, which didn't need this syntax.

Edit: Sorry, regex("\\\\.") seems to match nothing.

Edit2: Some code

void parser::lex(regex& token)
{
    // Skipping whitespaces
    {
        regex ws("\\s*");
        sregex_token_iterator wit(source.begin() + pos, source.end(), ws, regex_constants::match_default), wend;
        if(wit != wend)
            pos += (*wit).length();
    }

    sregex_token_iterator it(source.begin() + pos, source.end(), token, regex_constants::match_default), end;
    if (it != end)
        temp = *it;
    else
        temp = "";
}

Answer 1

This is because \. is interpreted as an escape sequence, which the language itself is trying to interpret as a single character. What you want is for your regex to contain the actual string "\.", which is written \\. because \\ is the escape sequence for the backslash character (\).