Cигнатура ?

include <iostream>
#include <functional>
#include <boost/function.hpp>
#include <boost/bind.hpp>
 
int main() {
  boost::function<int (int, int)> f = boost::bind<int>(std::plus<int>(), _1, _2);
  int result = f(1, 2); // result == 3
  
  std::cout<< result<< std::endl;
  
  return 0;