Added boost header

test/external/boost/signals2/last_value.hpp

@@ -0,0 +1,78 @@
+// 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