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// last_value function object (documented as part of Boost.Signals)
// Copyright Frank Mori Hess 2007.
// 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
#ifndef BOOST_SIGNALS2_LAST_VALUE_HPP
#define BOOST_SIGNALS2_LAST_VALUE_HPP
#include <boost/optional.hpp>
#include <boost/signals2/expired_slot.hpp>
#include <boost/throw_exception.hpp>
#include <stdexcept>
namespace boost {
namespace signals2 {
// no_slots_error is thrown when we are unable to generate a return value
// due to no slots being connected to the signal.
class no_slots_error: public std::exception
{
public:
virtual const char* what() const throw() {return "boost::signals2::no_slots_error";}
};
template<typename T>
class last_value {
public:
typedef T result_type;
template<typename InputIterator>
T operator()(InputIterator first, InputIterator last) const
{
if(first == last)
{
boost::throw_exception(no_slots_error());
}
optional<T> value;
while (first != last)
{
try
{
value = *first;
}
catch(const expired_slot &) {}
++first;
}
if(value) return value.get();
boost::throw_exception(no_slots_error());
}
};
template<>
class last_value<void> {
public:
typedef void result_type;
template<typename InputIterator>
result_type operator()(InputIterator first, InputIterator last) const
{
while (first != last)
{
try
{
*first;
}
catch(const expired_slot &) {}
++first;
}
return;
}
};
} // namespace signals2
} // namespace boost
#endif // BOOST_SIGNALS2_LAST_VALUE_HPP
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