maximum.cpp

An article on the implementation of a fast C++ delegate with many advanced features.

// FD.Delegate library examples

// Copyright Douglas Gregor 2001-2003. Use, modification and
// distribution is subject to the Boost Software License, Version
// 1.0. (See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)

// For more information, see http://www.boost.org

// Copyright (C) 2007 JaeWook Choi
// , modified from Boost.Signals maximum.cpp

#include <algorithm>
#include <iostream>
#include <boost/signals/signal2.hpp>
#include <fd/delegate/delegate2.hpp>
#include <vector>

template<typename T>
struct maximum {
  typedef T result_type;

  template<typename InputIterator>
  T operator()(InputIterator first, InputIterator last) const
  {
    if (first == last)
      throw std::runtime_error("Cannot compute maximum of zero elements!");
    return *std::max_element(first, last);
  }
};

int main()
{
  boost::signal2<int, int, int, maximum<int> > sig_max;
  sig_max.connect(std::plus<int>());
  sig_max.connect(std::multiplies<int>());
  sig_max.connect(std::minus<int>());
  sig_max.connect(std::divides<int>());

  std::cout << sig_max(5, 3) << std::endl; // prints 15

  fd::delegate2<int, int, int> dg_max;
  dg_max.add(std::plus<int>());
  dg_max += std::multiplies<int>();
  dg_max.add(std::minus<int>());
  dg_max += std::divides<int>();

  std::cout << dg_max(5, 3, maximum<int>()) << std::endl; // prints 15

  std::vector<int> vec_int;
  vec_int.push_back( std::plus<int>()(5, 3) );
  vec_int.push_back( std::multiplies<int>()(5, 3) );
  vec_int.push_back( std::minus<int>()(5, 3) );
  vec_int.push_back( std::divides<int>()(5, 3) );

  std::cout << maximum<int> ()(vec_int.begin(), vec_int.end()) << std::endl; // prints 15

  return 0;
}