[Boost-users] Having trouble with a callback function (converted to a class) in Regex

Subject: [Boost-users] Having trouble with a callback function (converted to a class) in Regex
From: Ramon F Herrera (ramon_at_[hidden])
Date: 2009-09-17 17:58:25

Hello,

This is my first non-trivial, multi-file C++ program with classes and I 
bumped into a problem. See example from the Regex library below.

The problem occurred after I converted the simple code below to a class 
(called "Pairs"). The troublesome statement is this one, where we 
attempt to take the address of a function.

std::for_each(m1, m2, &regex_callback);

My first compilation attempt produces an error message from the 
compiler, which is nice enough to offer a solution:

pairs.cpp:247: error: ISO C++ forbids taking the address of an 
unqualified or parenthesized non-static member func
tion to form a pointer to member function.  Say 
`&Pairs::assignment_callback'

So, following the compiler's suggestion, I changed the line above to this:

std::for_each(m1, m2, &Pairs::assignment_callback);

Now, I am getting an inscrutable (for me, anyway) error message:

stl_algo.h:158: error: must use .* or ->* to call pointer-to-member 
function in `__f (...)'

Thanks for your kind assistance,

-Ramon

===================================================

int main(int argc, const char** argv)
{
   std::string text;
   for(int i = 1; i < argc; ++i)
   {
   cout << "Processing file " << argv[i] << endl;
   std::ifstream fs(argv[i]);
   load_file(text, fs);
   // construct our iterators:
   boost::sregex_iterator m1(text.begin(), text.end(), expression);
   boost::sregex_iterator m2;
   std::for_each(m1, m2, &regex_callback);
   // copy results:
   cout << class_index.size() << " matches found" << endl;
   map_type::iterator c, d;
   c = class_index.begin();
   d = class_index.end();
   while(c != d)
   {
   cout << "class \"" << (*c).first << "\" found at index: " << 
(*c).second << endl;
  ++c;
  }
   class_index.erase(class_index.begin(), class_index.end());
   }
return 0;
}