[Boost-users] [mem_fn] Using mem_fn with std::bind2nd

From: Scott Meyers (usenet_at_[hidden])
Date: 2007-02-15 21:21:08

The mem_fn documentation is clear that there may be problems using 
mem_fn with the standard binders:

> mem_fn is not 100% compatible with the standard adaptors, although it comes pretty close. In particular, mem_fn  does not return objects of type std::[const_]mem_fun[1][_ref]_t, as the standard adaptors do, and it is not possible to fully describe the type of the first argument using the standard argument_type and first_argument_type  nested typedefs. Libraries that need adaptable function objects in order to function might not like mem_fn.

Fair enough.  The program below fails to compile with VC8 and g++ 4.1.1, 
and the VC8 error message (which I find much more readable than the g++ 
one) suggests that I'm running into the problem mentioned above. 
However, the program DOES compile using Comeau 4.3.8, and that's what 
confuses me.  Does anybody have any insights into whether this code is 
supposed to compile?  I'm especially interested in any remarks about 
whether it should compile using std::tr1::mem_fn, should there be any 
differences between that and boost::mem_fn.

Thanks,

Scott

#include <vector>
#include <algorithm>
#include <functional>
#include "boost/mem_fn.hpp"

struct Point {
   void rotate(int degrees);
};

int main()
{
   std::vector<Point> vp;

   std::for_each(vp.begin(), vp.end(),
                 std::bind2nd(boost::mem_fn(&Point::rotate), 10));
}