Re: [Boost-users] Iteratiing on regex results withpointer-to-member-function

From: John Maddock (john_at_[hidden])
Date: 2007-06-30 03:56:39

Alain Leblanc wrote:
> Hi,
>
> I wrote some code where I want to iterate on the result of a regex
> matching and call a member function for each match. It goes roughly
> like this:

> void XX::addDelayedVariables(string expr) {
> funcPtr = &XX::regex_callback;
> regex re("([[:alpha::]][[:alnum]]+)(\[[^\\]]+])");
> sregex_iterator m1(expr.begin(), expr.end(), re);
> sregex_iterator m2;
> match_results<string::const_iterator> results;  (*)
> bool a = (this->*funcPtr)(results);                    (*)
> for_each(m1, m2, (this->*funcPtr));                 (#)
> }
> ===========================================================================
>
> When compiling (gcc 4.1 on FC 6) I get an error message at (#) that
>    says: invalid use of non-static member function
>
> I added the two lines with a (*) as a sanity check to see that I
> declared the pointer-to-member-function correctly, and I have no
> problem compiling those.
>
> So my question is: is this a problem with me not understanding how to
> handle pointer-to-member-functions in C++, or is there something with
> the boost libraries that I'm missing or is preventing me from
> performing this operation? I would appreciate any help or opinion.

The problem is that (this->*funcPtr) is an unmentionable and unusable type 
in C++.  Yes, you can use it at the site of a function call, but not as a 
functor.

I'm sure Boost.Bind or Boost.Lambda have solutions, or you can use:

std::bind1st(std::mem_fun(&XX::regex_callback), this)

to create a valid functor to pass to for_each.

HTH, John.