Chris@16: /*
Chris@101:  *          Copyright Andrey Semashev 2007 - 2015.
Chris@16:  * Distributed under the Boost Software License, Version 1.0.
Chris@16:  *    (See accompanying file LICENSE_1_0.txt or copy at
Chris@16:  *          http://www.boost.org/LICENSE_1_0.txt)
Chris@16:  */
Chris@16: /*!
Chris@16:  * \file   value_ref.hpp
Chris@16:  * \author Andrey Semashev
Chris@16:  * \date   27.07.2012
Chris@16:  *
Chris@16:  * The header contains implementation of a value reference wrapper.
Chris@16:  */
Chris@16: 
Chris@16: #ifndef BOOST_LOG_UTILITY_VALUE_REF_HPP_INCLUDED_
Chris@16: #define BOOST_LOG_UTILITY_VALUE_REF_HPP_INCLUDED_
Chris@16: 
Chris@16: #include <cstddef>
Chris@16: #include <iosfwd>
Chris@16: #include <boost/assert.hpp>
Chris@16: #include <boost/mpl/if.hpp>
Chris@16: #include <boost/mpl/eval_if.hpp>
Chris@16: #include <boost/mpl/is_sequence.hpp>
Chris@16: #include <boost/mpl/front.hpp>
Chris@16: #include <boost/mpl/size.hpp>
Chris@16: #include <boost/mpl/int.hpp>
Chris@16: #include <boost/mpl/and.hpp>
Chris@16: #include <boost/mpl/identity.hpp>
Chris@16: #include <boost/mpl/equal_to.hpp>
Chris@16: #include <boost/mpl/contains.hpp>
Chris@16: #include <boost/mpl/index_of.hpp>
Chris@16: #include <boost/utility/addressof.hpp>
Chris@16: #include <boost/utility/enable_if.hpp>
Chris@16: #include <boost/optional/optional_fwd.hpp>
Chris@16: #include <boost/type_traits/is_same.hpp>
Chris@16: #include <boost/type_traits/is_void.hpp>
Chris@16: #include <boost/log/detail/config.hpp>
Chris@16: #include <boost/log/detail/parameter_tools.hpp>
Chris@16: #include <boost/log/detail/value_ref_visitation.hpp>
Chris@16: #include <boost/utility/explicit_operator_bool.hpp>
Chris@16: #include <boost/log/utility/formatting_ostream_fwd.hpp>
Chris@16: #include <boost/log/utility/functional/logical.hpp>
Chris@16: #include <boost/log/utility/functional/bind.hpp>
Chris@16: #include <boost/log/utility/functional/bind_output.hpp>
Chris@16: #include <boost/log/utility/functional/bind_to_log.hpp>
Chris@16: #include <boost/log/utility/manipulators/to_log.hpp>
Chris@16: #include <boost/log/utility/value_ref_fwd.hpp>
Chris@16: #include <boost/log/detail/header.hpp>
Chris@16: 
Chris@16: #ifdef BOOST_HAS_PRAGMA_ONCE
Chris@16: #pragma once
Chris@16: #endif
Chris@16: 
Chris@16: namespace boost {
Chris@16: 
Chris@16: BOOST_LOG_OPEN_NAMESPACE
Chris@16: 
Chris@16: namespace aux {
Chris@16: 
Chris@16: //! The function object applies the function object to the bound visitable object and argument
Chris@16: template< typename VisitableT, typename FunT >
Chris@16: struct vistation_invoker
Chris@16: {
Chris@16:     typedef typename FunT::result_type result_type;
Chris@16: 
Chris@16:     vistation_invoker(VisitableT& visitable, result_type const& def_val) : m_visitable(visitable), m_def_val(def_val)
Chris@16:     {
Chris@16:     }
Chris@16: 
Chris@16:     template< typename ArgT >
Chris@16:     result_type operator() (ArgT const& arg) const
Chris@16:     {
Chris@16:         return m_visitable.apply_visitor_or_default(binder1st< FunT, ArgT const& >(FunT(), arg), m_def_val);
Chris@16:     }
Chris@16: 
Chris@16: private:
Chris@16:     VisitableT& m_visitable;
Chris@16:     result_type m_def_val;
Chris@16: };
Chris@16: 
Chris@16: //! Attribute value reference implementation for a single type case
Chris@16: template< typename T, typename TagT >
Chris@16: class singular_ref
Chris@16: {
Chris@16: public:
Chris@16:     //! Referenced value type
Chris@16:     typedef T value_type;
Chris@16:     //! Tag type
Chris@16:     typedef TagT tag_type;
Chris@16: 
Chris@16: protected:
Chris@16:     //! The metafunction tests if the type is compatible with the reference wrapper
Chris@16: #if !defined(BOOST_NO_CXX11_TEMPLATE_ALIASES)
Chris@16:     template< typename U >
Chris@16:     using is_compatible = is_same< U, value_type >;
Chris@16: #else
Chris@16:     template< typename U >
Chris@16:     struct is_compatible :
Chris@16:         public is_same< U, value_type >
Chris@16:     {
Chris@16:     };
Chris@16: #endif
Chris@16: 
Chris@16: protected:
Chris@16:     //! Pointer to the value
Chris@16:     const value_type* m_ptr;
Chris@16: 
Chris@16: protected:
Chris@16:     //! Default constructor
Chris@16:     singular_ref() BOOST_NOEXCEPT : m_ptr(NULL)
Chris@16:     {
Chris@16:     }
Chris@16: 
Chris@16:     //! Initializing constructor
Chris@16:     explicit singular_ref(const value_type* p) BOOST_NOEXCEPT : m_ptr(p)
Chris@16:     {
Chris@16:     }
Chris@16: 
Chris@16: public:
Chris@16:     //! Returns a pointer to the referred value
Chris@16:     const value_type* operator-> () const BOOST_NOEXCEPT
Chris@16:     {
Chris@16:         BOOST_ASSERT(m_ptr != NULL);
Chris@16:         return m_ptr;
Chris@16:     }
Chris@16: 
Chris@16:     //! Returns a pointer to the referred value
Chris@16:     const value_type* get_ptr() const BOOST_NOEXCEPT
Chris@16:     {
Chris@16:         return m_ptr;
Chris@16:     }
Chris@16: 
Chris@16:     //! Returns a pointer to the referred value
Chris@16:     template< typename U >
Chris@16:     typename enable_if< is_compatible< U >, const U* >::type get_ptr() const BOOST_NOEXCEPT
Chris@16:     {
Chris@16:         return m_ptr;
Chris@16:     }
Chris@16: 
Chris@16:     //! Returns a reference to the value
Chris@16:     value_type const& operator* () const BOOST_NOEXCEPT
Chris@16:     {
Chris@16:         BOOST_ASSERT(m_ptr != NULL);
Chris@16:         return *m_ptr;
Chris@16:     }
Chris@16: 
Chris@16:     //! Returns a reference to the value
Chris@16:     value_type const& get() const BOOST_NOEXCEPT
Chris@16:     {
Chris@16:         BOOST_ASSERT(m_ptr != NULL);
Chris@16:         return *m_ptr;
Chris@16:     }
Chris@16: 
Chris@16:     //! Returns a reference to the value
Chris@16:     template< typename U >
Chris@16:     typename enable_if< is_compatible< U >, U const& >::type get() const BOOST_NOEXCEPT
Chris@16:     {
Chris@16:         BOOST_ASSERT(m_ptr != NULL);
Chris@16:         return *m_ptr;
Chris@16:     }
Chris@16: 
Chris@16: 
Chris@16:     //! Resets the reference
Chris@16:     void reset() BOOST_NOEXCEPT
Chris@16:     {
Chris@16:         m_ptr = NULL;
Chris@16:     }
Chris@16: 
Chris@16:     //! Returns the stored type index
Chris@16:     static BOOST_CONSTEXPR unsigned int which()
Chris@16:     {
Chris@16:         return 0u;
Chris@16:     }
Chris@16: 
Chris@16:     //! Swaps two reference wrappers
Chris@16:     void swap(singular_ref& that) BOOST_NOEXCEPT
Chris@16:     {
Chris@16:         const void* p = m_ptr;
Chris@16:         m_ptr = that.m_ptr;
Chris@16:         that.m_ptr = p;
Chris@16:     }
Chris@16: 
Chris@16:     //! Applies a visitor function object to the referred value
Chris@16:     template< typename VisitorT >
Chris@16:     typename VisitorT::result_type apply_visitor(VisitorT visitor) const
Chris@16:     {
Chris@16:         BOOST_ASSERT(m_ptr != NULL);
Chris@16:         return visitor(*m_ptr);
Chris@16:     }
Chris@16: 
Chris@16:     //! Applies a visitor function object to the referred value
Chris@16:     template< typename VisitorT >
Chris@16:     typename enable_if< is_void< typename VisitorT::result_type >, bool >::type apply_visitor_optional(VisitorT visitor) const
Chris@16:     {
Chris@16:         if (m_ptr)
Chris@16:         {
Chris@16:             visitor(*m_ptr);
Chris@16:             return true;
Chris@16:         }
Chris@16:         else
Chris@16:             return false;
Chris@16:     }
Chris@16: 
Chris@16:     //! Applies a visitor function object to the referred value
Chris@16:     template< typename VisitorT >
Chris@16:     typename disable_if< is_void< typename VisitorT::result_type >, optional< typename VisitorT::result_type > >::type apply_visitor_optional(VisitorT visitor) const
Chris@16:     {
Chris@16:         typedef optional< typename VisitorT::result_type > result_type;
Chris@16:         if (m_ptr)
Chris@16:             return result_type(visitor(*m_ptr));
Chris@16:         else
Chris@16:             return result_type();
Chris@16:     }
Chris@16: 
Chris@16:     //! Applies a visitor function object to the referred value or returns a default value
Chris@16:     template< typename VisitorT, typename DefaultT >
Chris@16:     typename VisitorT::result_type apply_visitor_or_default(VisitorT visitor, DefaultT& def_val) const
Chris@16:     {
Chris@16:         if (m_ptr)
Chris@16:             return visitor(*m_ptr);
Chris@16:         else
Chris@16:             return def_val;
Chris@16:     }
Chris@16: 
Chris@16:     //! Applies a visitor function object to the referred value or returns a default value
Chris@16:     template< typename VisitorT, typename DefaultT >
Chris@16:     typename VisitorT::result_type apply_visitor_or_default(VisitorT visitor, DefaultT const& def_val) const
Chris@16:     {
Chris@16:         if (m_ptr)
Chris@16:             return visitor(*m_ptr);
Chris@16:         else
Chris@16:             return def_val;
Chris@16:     }
Chris@16: };
Chris@16: 
Chris@16: //! Attribute value reference implementation for multiple types case
Chris@16: template< typename T, typename TagT >
Chris@16: class variant_ref
Chris@16: {
Chris@16: public:
Chris@16:     //! Referenced value type
Chris@16:     typedef T value_type;
Chris@16:     //! Tag type
Chris@16:     typedef TagT tag_type;
Chris@16: 
Chris@16: protected:
Chris@16:     //! The metafunction tests if the type is compatible with the reference wrapper
Chris@16: #if !defined(BOOST_NO_CXX11_TEMPLATE_ALIASES)
Chris@16:     template< typename U >
Chris@16:     using is_compatible = mpl::contains< value_type, U >;
Chris@16: #else
Chris@16:     template< typename U >
Chris@16:     struct is_compatible :
Chris@16:         public mpl::contains< value_type, U >
Chris@16:     {
Chris@16:     };
Chris@16: #endif
Chris@16: 
Chris@16: protected:
Chris@16:     //! Pointer to the value
Chris@16:     const void* m_ptr;
Chris@16:     //! Type index
Chris@16:     unsigned int m_type_idx;
Chris@16: 
Chris@16: protected:
Chris@16:     //! Default constructor
Chris@16:     variant_ref() BOOST_NOEXCEPT : m_ptr(NULL), m_type_idx(0)
Chris@16:     {
Chris@16:     }
Chris@16: 
Chris@16:     //! Initializing constructor
Chris@16:     template< typename U >
Chris@16:     explicit variant_ref(const U* p) BOOST_NOEXCEPT : m_ptr(p), m_type_idx(mpl::index_of< value_type, U >::type::value)
Chris@16:     {
Chris@16:     }
Chris@16: 
Chris@16: public:
Chris@16:     //! Resets the reference
Chris@16:     void reset() BOOST_NOEXCEPT
Chris@16:     {
Chris@16:         m_ptr = NULL;
Chris@16:         m_type_idx = 0;
Chris@16:     }
Chris@16: 
Chris@16:     //! Returns a pointer to the referred value
Chris@16:     template< typename U >
Chris@16:     typename enable_if< is_compatible< U >, const U* >::type get_ptr() const BOOST_NOEXCEPT
Chris@16:     {
Chris@16:         if (m_type_idx == static_cast< unsigned int >(mpl::index_of< value_type, U >::type::value))
Chris@16:             return static_cast< const U* >(m_ptr);
Chris@16:         else
Chris@16:             return NULL;
Chris@16:     }
Chris@16: 
Chris@16:     //! Returns a reference to the value
Chris@16:     template< typename U >
Chris@16:     typename enable_if< is_compatible< U >, U const& >::type get() const BOOST_NOEXCEPT
Chris@16:     {
Chris@16:         const U* const p = get_ptr< U >();
Chris@16:         BOOST_ASSERT(p != NULL);
Chris@16:         return *p;
Chris@16:     }
Chris@16: 
Chris@16:     //! Returns the stored type index
Chris@16:     unsigned int which() const BOOST_NOEXCEPT
Chris@16:     {
Chris@16:         return m_type_idx;
Chris@16:     }
Chris@16: 
Chris@16:     //! Swaps two reference wrappers
Chris@16:     void swap(variant_ref& that) BOOST_NOEXCEPT
Chris@16:     {
Chris@16:         const void* p = m_ptr;
Chris@16:         m_ptr = that.m_ptr;
Chris@16:         that.m_ptr = p;
Chris@16:         unsigned int type_idx = m_type_idx;
Chris@16:         m_type_idx = that.m_type_idx;
Chris@16:         that.m_type_idx = type_idx;
Chris@16:     }
Chris@16: 
Chris@16:     //! Applies a visitor function object to the referred value
Chris@16:     template< typename VisitorT >
Chris@16:     typename VisitorT::result_type apply_visitor(VisitorT visitor) const
Chris@16:     {
Chris@16:         BOOST_ASSERT(m_ptr != NULL);
Chris@16:         return do_apply_visitor(visitor);
Chris@16:     }
Chris@16: 
Chris@16:     //! Applies a visitor function object to the referred value
Chris@16:     template< typename VisitorT >
Chris@16:     typename enable_if< is_void< typename VisitorT::result_type >, bool >::type apply_visitor_optional(VisitorT visitor) const
Chris@16:     {
Chris@16:         if (m_ptr)
Chris@16:         {
Chris@16:             do_apply_visitor(visitor);
Chris@16:             return true;
Chris@16:         }
Chris@16:         else
Chris@16:             return false;
Chris@16:     }
Chris@16: 
Chris@16:     //! Applies a visitor function object to the referred value
Chris@16:     template< typename VisitorT >
Chris@16:     typename disable_if< is_void< typename VisitorT::result_type >, optional< typename VisitorT::result_type > >::type apply_visitor_optional(VisitorT visitor) const
Chris@16:     {
Chris@16:         typedef optional< typename VisitorT::result_type > result_type;
Chris@16:         if (m_ptr)
Chris@16:             return result_type(do_apply_visitor(visitor));
Chris@16:         else
Chris@16:             return result_type();
Chris@16:     }
Chris@16: 
Chris@16:     //! Applies a visitor function object to the referred value or returns a default value
Chris@16:     template< typename VisitorT, typename DefaultT >
Chris@16:     typename VisitorT::result_type apply_visitor_or_default(VisitorT visitor, DefaultT& def_val) const
Chris@16:     {
Chris@16:         if (m_ptr)
Chris@16:             return do_apply_visitor(visitor);
Chris@16:         else
Chris@16:             return def_val;
Chris@16:     }
Chris@16: 
Chris@16:     //! Applies a visitor function object to the referred value or returns a default value
Chris@16:     template< typename VisitorT, typename DefaultT >
Chris@16:     typename VisitorT::result_type apply_visitor_or_default(VisitorT visitor, DefaultT const& def_val) const
Chris@16:     {
Chris@16:         if (m_ptr)
Chris@16:             return do_apply_visitor(visitor);
Chris@16:         else
Chris@16:             return def_val;
Chris@16:     }
Chris@16: 
Chris@16: private:
Chris@16:     template< typename VisitorT >
Chris@16:     typename VisitorT::result_type do_apply_visitor(VisitorT& visitor) const
Chris@16:     {
Chris@16:         BOOST_ASSERT(m_type_idx < static_cast< unsigned int >(mpl::size< value_type >::value));
Chris@16:         return apply_visitor_dispatch< value_type, VisitorT >::call(m_ptr, m_type_idx, visitor);
Chris@16:     }
Chris@16: };
Chris@16: 
Chris@16: template< typename T, typename TagT >
Chris@16: struct value_ref_base
Chris@16: {
Chris@16:     typedef typename mpl::eval_if<
Chris@16:         mpl::and_< mpl::is_sequence< T >, mpl::equal_to< mpl::size< T >, mpl::int_< 1 > > >,
Chris@16:         mpl::front< T >,
Chris@16:         mpl::identity< T >
Chris@16:     >::type value_type;
Chris@16: 
Chris@16:     typedef typename mpl::if_<
Chris@16:         mpl::is_sequence< value_type >,
Chris@16:         variant_ref< value_type, TagT >,
Chris@16:         singular_ref< value_type, TagT >
Chris@16:     >::type type;
Chris@16: };
Chris@16: 
Chris@16: } // namespace aux
Chris@16: 
Chris@16: /*!
Chris@16:  * \brief Reference wrapper for a stored attribute value.
Chris@16:  *
Chris@16:  * The \c value_ref class template provides access to the stored attribute value. It is not a traditional reference wrapper
Chris@16:  * since it may be empty (i.e. refer to no value at all) and it can also refer to values of different types. Therefore its
Chris@16:  * interface and behavior combines features of Boost.Ref, Boost.Optional and Boost.Variant, depending on the use case.
Chris@16:  *
Chris@16:  * The template parameter \c T can be a single type or an MPL sequence of possible types being referred. The reference wrapper
Chris@16:  * will act as either an optional reference or an optional variant of references to the specified types. In any case, the
Chris@16:  * referred values will not be modifiable (i.e. \c value_ref always models a const reference).
Chris@16:  *
Chris@16:  * Template parameter \c TagT is optional. It can be used for customizing the operations on this reference wrapper, such as
Chris@16:  * putting the referred value to log.
Chris@16:  */
Chris@16: template< typename T, typename TagT >
Chris@16: class value_ref :
Chris@16:     public aux::value_ref_base< T, TagT >::type
Chris@16: {
Chris@16: #ifndef BOOST_LOG_DOXYGEN_PASS
Chris@16: public:
Chris@16:     typedef void _has_basic_formatting_ostream_insert_operator;
Chris@16: #endif
Chris@16: 
Chris@16: private:
Chris@16:     //! Base implementation type
Chris@16:     typedef typename aux::value_ref_base< T, TagT >::type base_type;
Chris@16: 
Chris@16: public:
Chris@16:     /*!
Chris@16:      * Default constructor. Creates a reference wrapper that does not refer to a value.
Chris@16:      */
Chris@16:     BOOST_DEFAULTED_FUNCTION(value_ref(), BOOST_NOEXCEPT {})
Chris@16: 
Chris@16:     /*!
Chris@16:      * Copy constructor.
Chris@16:      */
Chris@16:     BOOST_DEFAULTED_FUNCTION(value_ref(value_ref const& that), BOOST_NOEXCEPT : base_type(static_cast< base_type const& >(that)) {})
Chris@16: 
Chris@16:     /*!
Chris@16:      * Initializing constructor. Creates a reference wrapper that refers to the specified value.
Chris@16:      */
Chris@16:     template< typename U >
Chris@16:     explicit value_ref(U const& val, typename enable_if< typename base_type::BOOST_NESTED_TEMPLATE is_compatible< U >, int >::type = 0) BOOST_NOEXCEPT :
Chris@16:         base_type(boost::addressof(val))
Chris@16:     {
Chris@16:     }
Chris@16: 
Chris@16:     /*!
Chris@16:      * The operator verifies if the wrapper refers to a value.
Chris@16:      */
Chris@101:     BOOST_EXPLICIT_OPERATOR_BOOL_NOEXCEPT()
Chris@16: 
Chris@16:     /*!
Chris@16:      * The operator verifies if the wrapper does not refer to a value.
Chris@16:      */
Chris@16:     bool operator! () const BOOST_NOEXCEPT
Chris@16:     {
Chris@16:         return !this->m_ptr;
Chris@16:     }
Chris@16: 
Chris@16:     /*!
Chris@16:      * \return \c true if the wrapper does not refer to a value.
Chris@16:      */
Chris@16:     bool empty() const BOOST_NOEXCEPT
Chris@16:     {
Chris@16:         return !this->m_ptr;
Chris@16:     }
Chris@16: 
Chris@16:     /*!
Chris@16:      * Swaps two reference wrappers
Chris@16:      */
Chris@16:     void swap(value_ref& that) BOOST_NOEXCEPT
Chris@16:     {
Chris@16:         base_type::swap(that);
Chris@16:     }
Chris@16: };
Chris@16: 
Chris@16: //! Free swap function
Chris@16: template< typename T, typename TagT >
Chris@16: inline void swap(value_ref< T, TagT >& left, value_ref< T, TagT >& right)
Chris@16: {
Chris@16:     left.swap(right);
Chris@16: }
Chris@16: 
Chris@16: //! Stream output operator
Chris@16: template< typename CharT, typename TraitsT, typename T, typename TagT >
Chris@16: inline std::basic_ostream< CharT, TraitsT >& operator<< (std::basic_ostream< CharT, TraitsT >& strm, value_ref< T, TagT > const& val)
Chris@16: {
Chris@16:     if (!!val)
Chris@16:         val.apply_visitor(boost::log::bind_output(strm));
Chris@16:     return strm;
Chris@16: }
Chris@16: 
Chris@16: //! Log formatting operator
Chris@16: template< typename CharT, typename TraitsT, typename AllocatorT, typename T, typename TagT >
Chris@16: inline basic_formatting_ostream< CharT, TraitsT, AllocatorT >& operator<< (basic_formatting_ostream< CharT, TraitsT, AllocatorT >& strm, value_ref< T, TagT > const& val)
Chris@16: {
Chris@16:     if (!!val)
Chris@16:         val.apply_visitor(boost::log::bind_to_log< TagT >(strm));
Chris@16:     return strm;
Chris@16: }
Chris@16: 
Chris@16: // Equality comparison
Chris@16: template< typename T, typename TagT, typename U >
Chris@16: inline bool operator== (value_ref< T, TagT > const& left, U const& right)
Chris@16: {
Chris@16:     return left.apply_visitor_or_default(binder2nd< equal_to, U const& >(equal_to(), right), false);
Chris@16: }
Chris@16: 
Chris@16: template< typename U, typename T, typename TagT >
Chris@16: inline bool operator== (U const& left, value_ref< T, TagT > const& right)
Chris@16: {
Chris@16:     return right.apply_visitor_or_default(binder1st< equal_to, U const& >(equal_to(), left), false);
Chris@16: }
Chris@16: 
Chris@16: template< typename T1, typename TagT1, typename T2, typename TagT2 >
Chris@16: inline bool operator== (value_ref< T1, TagT1 > const& left, value_ref< T2, TagT2 > const& right)
Chris@16: {
Chris@16:     if (!left && !right)
Chris@16:         return true;
Chris@16:     return left.apply_visitor_or_default(aux::vistation_invoker< value_ref< T2, TagT2 >, equal_to >(right, false), false);
Chris@16: }
Chris@16: 
Chris@16: // Inequality comparison
Chris@16: template< typename T, typename TagT, typename U >
Chris@16: inline bool operator!= (value_ref< T, TagT > const& left, U const& right)
Chris@16: {
Chris@16:     return left.apply_visitor_or_default(binder2nd< not_equal_to, U const& >(not_equal_to(), right), false);
Chris@16: }
Chris@16: 
Chris@16: template< typename U, typename T, typename TagT >
Chris@16: inline bool operator!= (U const& left, value_ref< T, TagT > const& right)
Chris@16: {
Chris@16:     return right.apply_visitor_or_default(binder1st< not_equal_to, U const& >(not_equal_to(), left), false);
Chris@16: }
Chris@16: 
Chris@16: template< typename T1, typename TagT1, typename T2, typename TagT2 >
Chris@16: inline bool operator!= (value_ref< T1, TagT1 > const& left, value_ref< T2, TagT2 > const& right)
Chris@16: {
Chris@16:     if (!left && !right)
Chris@16:         return false;
Chris@16:     return left.apply_visitor_or_default(aux::vistation_invoker< value_ref< T2, TagT2 >, not_equal_to >(right, false), false);
Chris@16: }
Chris@16: 
Chris@16: // Less than ordering
Chris@16: template< typename T, typename TagT, typename U >
Chris@16: inline bool operator< (value_ref< T, TagT > const& left, U const& right)
Chris@16: {
Chris@16:     return left.apply_visitor_or_default(binder2nd< less, U const& >(less(), right), false);
Chris@16: }
Chris@16: 
Chris@16: template< typename U, typename T, typename TagT >
Chris@16: inline bool operator< (U const& left, value_ref< T, TagT > const& right)
Chris@16: {
Chris@16:     return right.apply_visitor_or_default(binder1st< less, U const& >(less(), left), false);
Chris@16: }
Chris@16: 
Chris@16: template< typename T1, typename TagT1, typename T2, typename TagT2 >
Chris@16: inline bool operator< (value_ref< T1, TagT1 > const& left, value_ref< T2, TagT2 > const& right)
Chris@16: {
Chris@16:     return left.apply_visitor_or_default(aux::vistation_invoker< value_ref< T2, TagT2 >, less >(right, false), false);
Chris@16: }
Chris@16: 
Chris@16: // Greater than ordering
Chris@16: template< typename T, typename TagT, typename U >
Chris@16: inline bool operator> (value_ref< T, TagT > const& left, U const& right)
Chris@16: {
Chris@16:     return left.apply_visitor_or_default(binder2nd< greater, U const& >(greater(), right), false);
Chris@16: }
Chris@16: 
Chris@16: template< typename U, typename T, typename TagT >
Chris@16: inline bool operator> (U const& left, value_ref< T, TagT > const& right)
Chris@16: {
Chris@16:     return right.apply_visitor_or_default(binder1st< greater, U const& >(greater(), left), false);
Chris@16: }
Chris@16: 
Chris@16: template< typename T1, typename TagT1, typename T2, typename TagT2 >
Chris@16: inline bool operator> (value_ref< T1, TagT1 > const& left, value_ref< T2, TagT2 > const& right)
Chris@16: {
Chris@16:     return left.apply_visitor_or_default(aux::vistation_invoker< value_ref< T2, TagT2 >, greater >(right, false), false);
Chris@16: }
Chris@16: 
Chris@16: // Less or equal ordering
Chris@16: template< typename T, typename TagT, typename U >
Chris@16: inline bool operator<= (value_ref< T, TagT > const& left, U const& right)
Chris@16: {
Chris@16:     return left.apply_visitor_or_default(binder2nd< less_equal, U const& >(less_equal(), right), false);
Chris@16: }
Chris@16: 
Chris@16: template< typename U, typename T, typename TagT >
Chris@16: inline bool operator<= (U const& left, value_ref< T, TagT > const& right)
Chris@16: {
Chris@16:     return right.apply_visitor_or_default(binder1st< less_equal, U const& >(less_equal(), left), false);
Chris@16: }
Chris@16: 
Chris@16: template< typename T1, typename TagT1, typename T2, typename TagT2 >
Chris@16: inline bool operator<= (value_ref< T1, TagT1 > const& left, value_ref< T2, TagT2 > const& right)
Chris@16: {
Chris@16:     if (!left && !right)
Chris@16:         return true;
Chris@16:     return left.apply_visitor_or_default(aux::vistation_invoker< value_ref< T2, TagT2 >, less_equal >(right, false), false);
Chris@16: }
Chris@16: 
Chris@16: // Greater or equal ordering
Chris@16: template< typename T, typename TagT, typename U >
Chris@16: inline bool operator>= (value_ref< T, TagT > const& left, U const& right)
Chris@16: {
Chris@16:     return left.apply_visitor_or_default(binder2nd< greater_equal, U const& >(greater_equal(), right), false);
Chris@16: }
Chris@16: 
Chris@16: template< typename U, typename T, typename TagT >
Chris@16: inline bool operator>= (U const& left, value_ref< T, TagT > const& right)
Chris@16: {
Chris@16:     return right.apply_visitor_or_default(binder1st< greater_equal, U const& >(greater_equal(), left), false);
Chris@16: }
Chris@16: 
Chris@16: template< typename T1, typename TagT1, typename T2, typename TagT2 >
Chris@16: inline bool operator>= (value_ref< T1, TagT1 > const& left, value_ref< T2, TagT2 > const& right)
Chris@16: {
Chris@16:     if (!left && !right)
Chris@16:         return true;
Chris@16:     return left.apply_visitor_or_default(aux::vistation_invoker< value_ref< T2, TagT2 >, greater_equal >(right, false), false);
Chris@16: }
Chris@16: 
Chris@16: BOOST_LOG_CLOSE_NAMESPACE // namespace log
Chris@16: 
Chris@16: } // namespace boost
Chris@16: 
Chris@16: #include <boost/log/detail/footer.hpp>
Chris@16: 
Chris@16: #endif // BOOST_LOG_UTILITY_VALUE_REF_HPP_INCLUDED_