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diff --git a/boost/accumulators/statistics/rolling_count.hpp b/boost/accumulators/statistics/rolling_count.hpp
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+++ b/boost/accumulators/statistics/rolling_count.hpp
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+///////////////////////////////////////////////////////////////////////////////
+// rolling_count.hpp
+//
+// Copyright 2008 Eric Niebler. Distributed under 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)
+
+#ifndef BOOST_ACCUMULATORS_STATISTICS_ROLLING_COUNT_HPP_EAN_26_12_2008
+#define BOOST_ACCUMULATORS_STATISTICS_ROLLING_COUNT_HPP_EAN_26_12_2008
+
+#include <boost/mpl/placeholders.hpp>
+#include <boost/accumulators/framework/accumulator_base.hpp>
+#include <boost/accumulators/framework/extractor.hpp>
+#include <boost/accumulators/numeric/functional.hpp>
+#include <boost/accumulators/framework/parameters/sample.hpp>
+#include <boost/accumulators/framework/depends_on.hpp>
+#include <boost/accumulators/statistics_fwd.hpp>
+#include <boost/accumulators/statistics/rolling_window.hpp>
+
+namespace boost { namespace accumulators
+{
+
+namespace impl
+{
+
+    ///////////////////////////////////////////////////////////////////////////////
+    // rolling_count_impl
+    //    returns the count of elements in the rolling window
+    template<typename Sample>
+    struct rolling_count_impl
+      : accumulator_base
+    {
+        typedef std::size_t result_type;
+
+        rolling_count_impl(dont_care)
+        {}
+
+        template<typename Args>
+        result_type result(Args const &args) const
+        {
+            return static_cast<std::size_t>(rolling_window_plus1(args).size()) - is_rolling_window_plus1_full(args);
+        }
+    };
+
+} // namespace impl
+
+///////////////////////////////////////////////////////////////////////////////
+// tag::rolling_count
+//
+namespace tag
+{
+    struct rolling_count
+      : depends_on< rolling_window_plus1 >
+    {
+        /// INTERNAL ONLY
+        ///
+        typedef accumulators::impl::rolling_count_impl< mpl::_1 > impl;
+
+        #ifdef BOOST_ACCUMULATORS_DOXYGEN_INVOKED
+        /// tag::rolling_window::window_size named parameter
+        static boost::parameter::keyword<tag::rolling_window_size> const window_size;
+        #endif
+    };
+} // namespace tag
+
+///////////////////////////////////////////////////////////////////////////////
+// extract::rolling_count
+//
+namespace extract
+{
+    extractor<tag::rolling_count> const rolling_count = {};
+
+    BOOST_ACCUMULATORS_IGNORE_GLOBAL(rolling_count)
+}
+
+using extract::rolling_count;
+
+}} // namespace boost::accumulators
+
+#endif