Chris@16: // last_value function object (documented as part of Boost.Signals)
Chris@16: 
Chris@16: // Copyright Frank Mori Hess 2007.
Chris@16: // Copyright Douglas Gregor 2001-2003. Use, modification and
Chris@16: // distribution is subject to the Boost Software License, Version
Chris@16: // 1.0. (See accompanying file LICENSE_1_0.txt or copy at
Chris@16: // http://www.boost.org/LICENSE_1_0.txt)
Chris@16: 
Chris@16: // For more information, see http://www.boost.org
Chris@16: 
Chris@16: #ifndef BOOST_SIGNALS2_LAST_VALUE_HPP
Chris@16: #define BOOST_SIGNALS2_LAST_VALUE_HPP
Chris@16: 
Chris@16: #include <boost/optional.hpp>
Chris@16: #include <boost/signals2/expired_slot.hpp>
Chris@16: #include <boost/throw_exception.hpp>
Chris@16: #include <stdexcept>
Chris@16: 
Chris@16: namespace boost {
Chris@16:   namespace signals2 {
Chris@16: 
Chris@16:     // no_slots_error is thrown when we are unable to generate a return value
Chris@16:     // due to no slots being connected to the signal.
Chris@16:     class no_slots_error: public std::exception
Chris@16:     {
Chris@16:     public:
Chris@16:       virtual const char* what() const throw() {return "boost::signals2::no_slots_error";}
Chris@16:     };
Chris@16: 
Chris@16:     template<typename T>
Chris@16:     class last_value {
Chris@16:     public:
Chris@16:       typedef T result_type;
Chris@16: 
Chris@16:       template<typename InputIterator>
Chris@16:       T operator()(InputIterator first, InputIterator last) const
Chris@16:       {
Chris@16:         if(first == last)
Chris@16:         {
Chris@16:           boost::throw_exception(no_slots_error());
Chris@16:         }
Chris@16:         optional<T> value;
Chris@16:         while (first != last)
Chris@16:         {
Chris@16:           try
Chris@16:           {
Chris@16:             value = *first;
Chris@16:           }
Chris@16:           catch(const expired_slot &) {}
Chris@16:           ++first;
Chris@16:         }
Chris@16:         if(value) return value.get();
Chris@16:         boost::throw_exception(no_slots_error());
Chris@16:       }
Chris@16:     };
Chris@16: 
Chris@16:     template<>
Chris@16:     class last_value<void> {
Chris@16:     public:
Chris@16:       typedef void result_type;
Chris@16:       template<typename InputIterator>
Chris@16:         result_type operator()(InputIterator first, InputIterator last) const
Chris@16:       {
Chris@16:         while (first != last)
Chris@16:         {
Chris@16:           try
Chris@16:           {
Chris@16:             *first;
Chris@16:           }
Chris@16:           catch(const expired_slot &) {}
Chris@16:           ++first;
Chris@16:         }
Chris@16:         return;
Chris@16:       }
Chris@16:     };
Chris@16:   } // namespace signals2
Chris@16: } // namespace boost
Chris@16: #endif // BOOST_SIGNALS2_LAST_VALUE_HPP