| // Boost.Signals library |
| |
| // 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 |
| |
| #include <boost/signals/signal2.hpp> |
| #include <iostream> |
| |
| template<typename T> |
| struct first_positive { |
| typedef T result_type; |
| |
| template<typename InputIterator> |
| T operator()(InputIterator first, InputIterator last) const |
| { |
| while (first != last && !(*first > 0)) { ++first; } |
| return (first == last) ? 0 |
| : *first; |
| } |
| }; |
| |
| template<typename T> |
| struct noisy_divide { |
| typedef T result_type; |
| |
| T operator()(const T& x, const T& y) const |
| { |
| std::cout << "Dividing " << x << " and " << y << std::endl; |
| return x/y; |
| } |
| }; |
| |
| int main() |
| { |
| boost::signal2<int, int, int, first_positive<int> > sig_positive; |
| sig_positive.connect(std::plus<int>()); |
| sig_positive.connect(std::multiplies<int>()); |
| sig_positive.connect(std::minus<int>()); |
| sig_positive.connect(noisy_divide<int>()); |
| |
| assert(sig_positive(3, -5) == 8); // returns 8, but prints nothing |
| |
| return 0; |
| } |