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+#ifndef BOOST_CORE_REF_HPP
+#define BOOST_CORE_REF_HPP
+
+// MS compatible compilers support #pragma once
+
+#if defined(_MSC_VER) && (_MSC_VER >= 1020)
+# pragma once
+#endif
+
+#include <boost/config.hpp>
+#include <boost/utility/addressof.hpp>
+#include <boost/detail/workaround.hpp>
+
+//
+// ref.hpp - ref/cref, useful helper functions
+//
+// Copyright (C) 1999, 2000 Jaakko Jarvi (jaakko.jarvi@cs.utu.fi)
+// Copyright (C) 2001, 2002 Peter Dimov
+// Copyright (C) 2002 David Abrahams
+//
+// Copyright (C) 2014 Glen Joseph Fernandes
+// glenfe at live dot com
+// Copyright (C) 2014 Agustin Berge
+//
+// 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)
+//
+// See http://www.boost.org/libs/core/doc/html/core/ref.html for documentation.
+//
+
+/**
+ @file
+*/
+
+/**
+ Boost namespace.
+*/
+namespace boost
+{
+
+#if defined( BOOST_MSVC ) && BOOST_WORKAROUND( BOOST_MSVC, == 1600 )
+
+ struct ref_workaround_tag {};
+
+#endif
+
+// reference_wrapper
+
+/**
+ @brief Contains a reference to an object of type `T`.
+
+ `reference_wrapper` is primarily used to "feed" references to
+ function templates (algorithms) that take their parameter by
+ value. It provides an implicit conversion to `T&`, which
+ usually allows the function templates to work on references
+ unmodified.
+*/
+template<class T> class reference_wrapper
+{
+public:
+ /**
+ Type `T`.
+ */
+ typedef T type;
+
+ /**
+ Constructs a `reference_wrapper` object that stores a
+ reference to `t`.
+
+ @remark Does not throw.
+ */
+ BOOST_FORCEINLINE explicit reference_wrapper(T& t): t_(boost::addressof(t)) {}
+
+#if defined( BOOST_MSVC ) && BOOST_WORKAROUND( BOOST_MSVC, == 1600 )
+
+ BOOST_FORCEINLINE explicit reference_wrapper( T & t, ref_workaround_tag ): t_( boost::addressof( t ) ) {}
+
+#endif
+
+#if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
+ /**
+ @remark Construction from a temporary object is disabled.
+ */
+ BOOST_DELETED_FUNCTION(reference_wrapper(T&& t))
+public:
+#endif
+
+ /**
+ @return The stored reference.
+ @remark Does not throw.
+ */
+ BOOST_FORCEINLINE operator T& () const { return *t_; }
+
+ /**
+ @return The stored reference.
+ @remark Does not throw.
+ */
+ BOOST_FORCEINLINE T& get() const { return *t_; }
+
+ /**
+ @return A pointer to the object referenced by the stored
+ reference.
+ @remark Does not throw.
+ */
+ BOOST_FORCEINLINE T* get_pointer() const { return t_; }
+
+private:
+
+ T* t_;
+};
+
+// ref
+
+/**
+ @cond
+*/
+#if defined( __BORLANDC__ ) && BOOST_WORKAROUND( __BORLANDC__, BOOST_TESTED_AT(0x581) )
+# define BOOST_REF_CONST
+#else
+# define BOOST_REF_CONST const
+#endif
+/**
+ @endcond
+*/
+
+/**
+ @return `reference_wrapper<T>(t)`
+ @remark Does not throw.
+*/
+template<class T> BOOST_FORCEINLINE reference_wrapper<T> BOOST_REF_CONST ref( T & t )
+{
+#if defined( BOOST_MSVC ) && BOOST_WORKAROUND( BOOST_MSVC, == 1600 )
+
+ return reference_wrapper<T>( t, ref_workaround_tag() );
+
+#else
+
+ return reference_wrapper<T>( t );
+
+#endif
+}
+
+// cref
+
+/**
+ @return `reference_wrapper<T const>(t)`
+ @remark Does not throw.
+*/
+template<class T> BOOST_FORCEINLINE reference_wrapper<T const> BOOST_REF_CONST cref( T const & t )
+{
+ return reference_wrapper<T const>(t);
+}
+
+#undef BOOST_REF_CONST
+
+#if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
+
+/**
+ @cond
+*/
+#if defined(BOOST_NO_CXX11_DELETED_FUNCTIONS)
+# define BOOST_REF_DELETE
+#else
+# define BOOST_REF_DELETE = delete
+#endif
+/**
+ @endcond
+*/
+
+/**
+ @remark Construction from a temporary object is disabled.
+*/
+template<class T> void ref(T const&&) BOOST_REF_DELETE;
+
+/**
+ @remark Construction from a temporary object is disabled.
+*/
+template<class T> void cref(T const&&) BOOST_REF_DELETE;
+
+#undef BOOST_REF_DELETE
+
+#endif
+
+// is_reference_wrapper
+
+/**
+ @brief Determine if a type `T` is an instantiation of
+ `reference_wrapper`.
+
+ The value static constant will be true if the type `T` is a
+ specialization of `reference_wrapper`.
+*/
+template<typename T> struct is_reference_wrapper
+{
+ BOOST_STATIC_CONSTANT( bool, value = false );
+};
+
+/**
+ @cond
+*/
+template<typename T> struct is_reference_wrapper< reference_wrapper<T> >
+{
+ BOOST_STATIC_CONSTANT( bool, value = true );
+};
+
+#if !defined(BOOST_NO_CV_SPECIALIZATIONS)
+
+template<typename T> struct is_reference_wrapper< reference_wrapper<T> const >
+{
+ BOOST_STATIC_CONSTANT( bool, value = true );
+};
+
+template<typename T> struct is_reference_wrapper< reference_wrapper<T> volatile >
+{
+ BOOST_STATIC_CONSTANT( bool, value = true );
+};
+
+template<typename T> struct is_reference_wrapper< reference_wrapper<T> const volatile >
+{
+ BOOST_STATIC_CONSTANT( bool, value = true );
+};
+
+#endif // !defined(BOOST_NO_CV_SPECIALIZATIONS)
+
+/**
+ @endcond
+*/
+
+
+// unwrap_reference
+
+/**
+ @brief Find the type in a `reference_wrapper`.
+
+ The `typedef` type is `T::type` if `T` is a
+ `reference_wrapper`, `T` otherwise.
+*/
+template<typename T> struct unwrap_reference
+{
+ typedef T type;
+};
+
+/**
+ @cond
+*/
+template<typename T> struct unwrap_reference< reference_wrapper<T> >
+{
+ typedef T type;
+};
+
+#if !defined(BOOST_NO_CV_SPECIALIZATIONS)
+
+template<typename T> struct unwrap_reference< reference_wrapper<T> const >
+{
+ typedef T type;
+};
+
+template<typename T> struct unwrap_reference< reference_wrapper<T> volatile >
+{
+ typedef T type;
+};
+
+template<typename T> struct unwrap_reference< reference_wrapper<T> const volatile >
+{
+ typedef T type;
+};
+
+#endif // !defined(BOOST_NO_CV_SPECIALIZATIONS)
+
+/**
+ @endcond
+*/
+
+// unwrap_ref
+
+/**
+ @return `unwrap_reference<T>::type&(t)`
+ @remark Does not throw.
+*/
+template<class T> BOOST_FORCEINLINE typename unwrap_reference<T>::type& unwrap_ref( T & t )
+{
+ return t;
+}
+
+// get_pointer
+
+/**
+ @cond
+*/
+template<class T> BOOST_FORCEINLINE T* get_pointer( reference_wrapper<T> const & r )
+{
+ return r.get_pointer();
+}
+/**
+ @endcond
+*/
+
+} // namespace boost
+
+#endif // #ifndef BOOST_CORE_REF_HPP