Re: [boost] [xpressive] regex_replace() issue.

From: Robert Dailey (rcdailey_at_[hidden])
Date: 2008-03-16 20:39:33

On Sun, Mar 16, 2008 at 5:44 PM, Eric Niebler <eric_at_[hidden]>
wrote:

> Eric Niebler wrote:
> >
> > The formatter can be a function object, or even just a plain function.
> > So, for instance, you can do this:
> >
> >    map<string,string> replacements;
> >
> >    string my_format(smatch const &what)
> >    {
> >        return replacements[what[0].str()];
> >    }
> >
> >    int main()
> >    {
> >        string input = ...;
> >        sregex rx = ...;
> >        string output = regex_replace(input, rx, my_format);
> >    }
> >
>
> I've made a small addition ... the formatter can be a lambda, too, if
> you #include <boost/xpressive/regex_actions.hpp>. The above can now be
> written simply as:
>
>   using xpressive::ref;
>   string output = regex_replace(input, rx, ref(replacements)[_]);
>
> Here, "_" gets substituted with a sub_match representing the current
> match. You can also use s1, s2, etc., to access the other sub-matches.

How is "[_]" legal C++ syntax?