[Boost-users] comparing function objects

Subject: [Boost-users] comparing function objects
From: Noah Roberts (roberts.noah_at_[hidden])
Date: 2008-09-24 18:35:16

"Function object wrappers can be compared via ==  or != against any 
function object that can be stored within the wrapper. If the function 
object wrapper contains a function object of that type, it will be 
compared against the given function object (which must be either be 
EqualityComparable or have an overloaded boost::function_equal)."

But how do I compare two boost::functions?  This code doesn't work:

#include <boost/function.hpp>
#include <boost/bind.hpp>

double f(double)
{
   return 42.0;
}

int main()
{
   boost::function<double(double)> f1 = boost::bind(&f, _1);
   boost::function<double(double)> f2 = boost::bind(&f, _1);

   //if (f1 == f2)
   if (boost::function_equal<boost::function<double(double)>, 
boost::function<double(double)> >(f1,f2))
    ;
}

NOTE: tried to specifically instantiate the function_equal template as 
attempt3.  Previous attempt didn't do that...it also did not work.