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 // Copyright (C) 2003, 2008 Fernando Luis Cacciola Carballal.
 // Copyright (C) 2014-2016 Andrzej Krzemienski.
 //
 // 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)
 //
 // See http://www.boost.org/libs/optional for documentation.
 //
 // You are welcome to contact the maintainer at:
 //  akrzemi1@gmail.com
 
 #ifndef BOOST_OPTIONAL_DETAIL_OLD_OPTIONAL_IMPLEMENTATION_AJK_28JAN2015_HPP
 #define BOOST_OPTIONAL_DETAIL_OLD_OPTIONAL_IMPLEMENTATION_AJK_28JAN2015_HPP
 
 #include <boost/detail/reference_content.hpp>
 #include <boost/type_traits/is_reference.hpp>
 #include <boost/type_traits/integral_constant.hpp>
 #include <boost/type_traits/conditional.hpp>
 #include <boost/core/invoke_swap.hpp>
 
 namespace boost {
 
 namespace optional_detail {
 
 
 template<class T>
 struct types_when_isnt_ref
 {
   typedef T const& reference_const_type ;
   typedef T &      reference_type ;
 #ifndef  BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
   typedef T &&     rval_reference_type ;
   typedef T &&     reference_type_of_temporary_wrapper;
 #ifdef BOOST_MOVE_OLD_RVALUE_REF_BINDING_RULES
   // GCC 4.4 has support for an early draft of rvalue references. The conforming version below
   // causes warnings about returning references to a temporary.
   static T&& move(T&& r) { return r; }
 #else
   static rval_reference_type move(reference_type r) { return boost::move(r); }
 #endif
 #endif
   typedef T const* pointer_const_type ;
   typedef T *      pointer_type ;
   typedef T const& argument_type ;
 } ;
 
 template<class T>
 struct types_when_is_ref
 {
   typedef BOOST_DEDUCED_TYPENAME remove_reference<T>::type raw_type ;
 
   typedef raw_type&  reference_const_type ;
   typedef raw_type&  reference_type ;
 #ifndef  BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
   typedef BOOST_DEDUCED_TYPENAME remove_const<raw_type>::type&& rval_reference_type ;
   typedef raw_type&  reference_type_of_temporary_wrapper;
   static reference_type move(reference_type r) { return r; }
 #endif
   typedef raw_type*  pointer_const_type ;
   typedef raw_type*  pointer_type ;
   typedef raw_type&  argument_type ;
 } ;
 
 template <class To, class From>
 void prevent_binding_rvalue_ref_to_optional_lvalue_ref()
 {
 #ifndef BOOST_OPTIONAL_CONFIG_ALLOW_BINDING_TO_RVALUES
   BOOST_STATIC_ASSERT_MSG(
     !boost::is_lvalue_reference<To>::value || !boost::is_rvalue_reference<From>::value, 
     "binding rvalue references to optional lvalue references is disallowed");
 #endif    
 }
 
 struct optional_tag {} ;
 
 template<class T>
 class optional_base : public optional_tag
 {
   private :
 
     typedef
 #if !BOOST_WORKAROUND(BOOST_BORLANDC, BOOST_TESTED_AT(0x564))
     BOOST_DEDUCED_TYPENAME
 #endif
     ::boost::detail::make_reference_content<T>::type internal_type ;
 
     typedef aligned_storage<internal_type> storage_type ;
 
     typedef types_when_isnt_ref<T> types_when_not_ref ;
     typedef types_when_is_ref<T>   types_when_ref   ;
 
     typedef optional_base<T> this_type ;
 
   protected :
 
     typedef T value_type ;
 
     typedef true_type  is_reference_tag ;
     typedef false_type is_not_reference_tag ;
 
     typedef BOOST_DEDUCED_TYPENAME is_reference<T>::type is_reference_predicate ;
 
   public:
     typedef BOOST_DEDUCED_TYPENAME conditional<is_reference_predicate::value,types_when_ref,types_when_not_ref>::type types ;
 
   protected:
     typedef BOOST_DEDUCED_TYPENAME types::reference_type       reference_type ;
     typedef BOOST_DEDUCED_TYPENAME types::reference_const_type reference_const_type ;
 #ifndef  BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
     typedef BOOST_DEDUCED_TYPENAME types::rval_reference_type  rval_reference_type ;
     typedef BOOST_DEDUCED_TYPENAME types::reference_type_of_temporary_wrapper reference_type_of_temporary_wrapper ;
 #endif
     typedef BOOST_DEDUCED_TYPENAME types::pointer_type         pointer_type ;
     typedef BOOST_DEDUCED_TYPENAME types::pointer_const_type   pointer_const_type ;
     typedef BOOST_DEDUCED_TYPENAME types::argument_type        argument_type ;
 
     // Creates an optional<T> uninitialized.
     // No-throw
     optional_base()
       :
       m_initialized(false) {}
 
     // Creates an optional<T> uninitialized.
     // No-throw
     optional_base ( none_t )
       :
       m_initialized(false) {}
 
     // Creates an optional<T> initialized with 'val'.
     // Can throw if T::T(T const&) does
     optional_base ( argument_type val )
       :
       m_initialized(false)
     {
         construct(val);
     }
 
 #ifndef  BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
     // move-construct an optional<T> initialized from an rvalue-ref to 'val'.
     // Can throw if T::T(T&&) does
     optional_base ( rval_reference_type val )
       :
       m_initialized(false)
     {
       construct( boost::move(val) );
     }
 #endif
 
     // Creates an optional<T> initialized with 'val' IFF cond is true, otherwise creates an uninitialized optional<T>.
     // Can throw if T::T(T const&) does
     optional_base ( bool cond, argument_type val )
       :
       m_initialized(false)
     {
       if ( cond )
         construct(val);
     }
 
     // Creates a deep copy of another optional<T>
     // Can throw if T::T(T const&) does
     optional_base ( optional_base const& rhs )
       :
       m_initialized(false)
     {
       if ( rhs.is_initialized() )
         construct(rhs.get_impl());
     }
 
 #ifndef  BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
     // Creates a deep move of another optional<T>
     // Can throw if T::T(T&&) does
     optional_base ( optional_base&& rhs )
       :
       m_initialized(false)
     {
       if ( rhs.is_initialized() )
         construct( boost::move(rhs.get_impl()) );
     }
 #endif
 
 #ifndef  BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
 
     template<class Expr, class PtrExpr>
     explicit optional_base ( Expr&& expr, PtrExpr const* tag )
       :
       m_initialized(false)
     {
       construct(boost::forward<Expr>(expr),tag);
     }
 
 #else
     // This is used for both converting and in-place constructions.
     // Derived classes use the 'tag' to select the appropriate
     // implementation (the correct 'construct()' overload)
     template<class Expr>
     explicit optional_base ( Expr const& expr, Expr const* tag )
       :
       m_initialized(false)
     {
       construct(expr,tag);
     }
 
 #endif
 
 
     // No-throw (assuming T::~T() doesn't)
     ~optional_base() { destroy() ; }
 
     // Assigns from another optional<T> (deep-copies the rhs value)
     void assign ( optional_base const& rhs )
     {
       if (is_initialized())
       {
         if ( rhs.is_initialized() )
              assign_value(rhs.get_impl(), is_reference_predicate() );
         else destroy();
       }
       else
       {
         if ( rhs.is_initialized() )
           construct(rhs.get_impl());
       }
     }
     
 #ifndef BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
     // Assigns from another optional<T> (deep-moves the rhs value)
     void assign ( optional_base&& rhs )
     {
       if (is_initialized())
       {
         if ( rhs.is_initialized() )
              assign_value(boost::move(rhs.get_impl()), is_reference_predicate() );
         else destroy();
       }
       else
       {
         if ( rhs.is_initialized() )
           construct(boost::move(rhs.get_impl()));
       }
     }
 #endif 
 
     // Assigns from another _convertible_ optional<U> (deep-copies the rhs value)
     template<class U>
     void assign ( optional<U> const& rhs )
     {
       if (is_initialized())
       {
         if ( rhs.is_initialized() )
 #ifndef BOOST_OPTIONAL_CONFIG_RESTORE_ASSIGNMENT_OF_NONCONVERTIBLE_TYPES
           assign_value(rhs.get(), is_reference_predicate() );
 #else
           assign_value(static_cast<value_type>(rhs.get()), is_reference_predicate() );
 #endif
           
         else destroy();
       }
       else
       {
         if ( rhs.is_initialized() )
 #ifndef BOOST_OPTIONAL_CONFIG_RESTORE_ASSIGNMENT_OF_NONCONVERTIBLE_TYPES
           construct(rhs.get());
 #else
           construct(static_cast<value_type>(rhs.get()));
 #endif
       }
     }
 
 #ifndef BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
     // move-assigns from another _convertible_ optional<U> (deep-moves from the rhs value)
     template<class U>
     void assign ( optional<U>&& rhs )
     {
       typedef BOOST_DEDUCED_TYPENAME optional<U>::rval_reference_type ref_type;
       if (is_initialized())
       {
         if ( rhs.is_initialized() )
              assign_value(static_cast<ref_type>(rhs.get()), is_reference_predicate() );
         else destroy();
       }
       else
       {
         if ( rhs.is_initialized() )
           construct(static_cast<ref_type>(rhs.get()));
       }
     }
 #endif
     
     // Assigns from a T (deep-copies the rhs value)
     void assign ( argument_type val )
     {
       if (is_initialized())
            assign_value(val, is_reference_predicate() );
       else construct(val);
     }
     
 #ifndef BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
     // Assigns from a T (deep-moves the rhs value)
     void assign ( rval_reference_type val )
     {
       if (is_initialized())
            assign_value( boost::move(val), is_reference_predicate() );
       else construct( boost::move(val) );
     }
 #endif
 
     // Assigns from "none", destroying the current value, if any, leaving this UNINITIALIZED
     // No-throw (assuming T::~T() doesn't)
     void assign ( none_t ) BOOST_NOEXCEPT { destroy(); }
 
 #ifndef BOOST_OPTIONAL_NO_INPLACE_FACTORY_SUPPORT
 
 #ifndef BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
     template<class Expr, class ExprPtr>
     void assign_expr ( Expr&& expr, ExprPtr const* tag )
     {
       if (is_initialized())
         assign_expr_to_initialized(boost::forward<Expr>(expr),tag);
       else construct(boost::forward<Expr>(expr),tag);
     }
 #else
     template<class Expr>
     void assign_expr ( Expr const& expr, Expr const* tag )
     {
       if (is_initialized())
         assign_expr_to_initialized(expr,tag);
       else construct(expr,tag);
     }
 #endif
 
 #endif
 
   public :
 
     // Destroys the current value, if any, leaving this UNINITIALIZED
     // No-throw (assuming T::~T() doesn't)
     void reset() BOOST_NOEXCEPT { destroy(); }
 
     // **DEPRECATED** Replaces the current value -if any- with 'val'
     void reset ( argument_type val ) { assign(val); }
 
     // Returns a pointer to the value if this is initialized, otherwise,
     // returns NULL.
     // No-throw
     pointer_const_type get_ptr() const { return m_initialized ? get_ptr_impl() : 0 ; }
     pointer_type       get_ptr()       { return m_initialized ? get_ptr_impl() : 0 ; }
 
     bool is_initialized() const { return m_initialized ; }
 
   protected :
 
     void construct ( argument_type val )
      {
        ::new (m_storage.address()) internal_type(val) ;
        m_initialized = true ;
      }
      
 #ifndef  BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
     void construct ( rval_reference_type val )
      {
        ::new (m_storage.address()) internal_type( types::move(val) ) ;
        m_initialized = true ;
      }
 #endif
 
 
 #if (!defined BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES) && (!defined BOOST_NO_CXX11_VARIADIC_TEMPLATES)
     // Constructs in-place
     // upon exception *this is always uninitialized
     template<class... Args>
     void emplace_assign ( Args&&... args )
      {
        destroy();
        ::new (m_storage.address()) internal_type( boost::forward<Args>(args)... );
        m_initialized = true ;
      }
 #elif (!defined BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES)
     template<class Arg>
     void emplace_assign ( Arg&& arg )
      {
        destroy();
        ::new (m_storage.address()) internal_type( boost::forward<Arg>(arg) );
        m_initialized = true ;
      }
      
     void emplace_assign ()
      {
        destroy();
        ::new (m_storage.address()) internal_type();
        m_initialized = true ;
      }
 #else
     template<class Arg>
     void emplace_assign ( const Arg& arg )
      {
        destroy();
        ::new (m_storage.address()) internal_type( arg );
        m_initialized = true ;
      }
      
     template<class Arg>
     void emplace_assign ( Arg& arg )
      {
        destroy();
        ::new (m_storage.address()) internal_type( arg );
        m_initialized = true ;
      }
      
     void emplace_assign ()
      {
        destroy();
        ::new (m_storage.address()) internal_type();
        m_initialized = true ;
      }
 #endif
 
 #ifndef BOOST_OPTIONAL_NO_INPLACE_FACTORY_SUPPORT
 
 #ifndef BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
     // Constructs in-place using the given factory
     template<class Expr>
     void construct ( Expr&& factory, in_place_factory_base const* )
      {
        BOOST_STATIC_ASSERT ( !is_reference_predicate::value ) ;
        boost_optional_detail::construct<value_type>(factory, m_storage.address());
        m_initialized = true ;
      }
 
     // Constructs in-place using the given typed factory
     template<class Expr>
     void construct ( Expr&& factory, typed_in_place_factory_base const* )
      {
        BOOST_STATIC_ASSERT ( !is_reference_predicate::value ) ;
        factory.apply(m_storage.address()) ;
        m_initialized = true ;
      }
 
     template<class Expr>
     void assign_expr_to_initialized ( Expr&& factory, in_place_factory_base const* tag )
      {
        destroy();
        construct(factory,tag);
      }
 
     // Constructs in-place using the given typed factory
     template<class Expr>
     void assign_expr_to_initialized ( Expr&& factory, typed_in_place_factory_base const* tag )
      {
        destroy();
        construct(factory,tag);
      }
 
 #else
     // Constructs in-place using the given factory
     template<class Expr>
     void construct ( Expr const& factory, in_place_factory_base const* )
      {
        BOOST_STATIC_ASSERT ( !is_reference_predicate::value ) ;
        boost_optional_detail::construct<value_type>(factory, m_storage.address());
        m_initialized = true ;
      }
 
     // Constructs in-place using the given typed factory
     template<class Expr>
     void construct ( Expr const& factory, typed_in_place_factory_base const* )
      {
        BOOST_STATIC_ASSERT ( !is_reference_predicate::value ) ;
        factory.apply(m_storage.address()) ;
        m_initialized = true ;
      }
 
     template<class Expr>
     void assign_expr_to_initialized ( Expr const& factory, in_place_factory_base const* tag )
      {
        destroy();
        construct(factory,tag);
      }
 
     // Constructs in-place using the given typed factory
     template<class Expr>
     void assign_expr_to_initialized ( Expr const& factory, typed_in_place_factory_base const* tag )
      {
        destroy();
        construct(factory,tag);
      }
 #endif
 
 #endif
 
 #ifndef BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
     // Constructs using any expression implicitly convertible to the single argument
     // of a one-argument T constructor.
     // Converting constructions of optional<T> from optional<U> uses this function with
     // 'Expr' being of type 'U' and relying on a converting constructor of T from U.
     template<class Expr>
     void construct ( Expr&& expr, void const* )
     {
       new (m_storage.address()) internal_type(boost::forward<Expr>(expr)) ;
       m_initialized = true ;
     }
 
     // Assigns using a form any expression implicitly convertible to the single argument
     // of a T's assignment operator.
     // Converting assignments of optional<T> from optional<U> uses this function with
     // 'Expr' being of type 'U' and relying on a converting assignment of T from U.
     template<class Expr>
     void assign_expr_to_initialized ( Expr&& expr, void const* )
     {
       assign_value(boost::forward<Expr>(expr), is_reference_predicate());
     }
 #else
     // Constructs using any expression implicitly convertible to the single argument
     // of a one-argument T constructor.
     // Converting constructions of optional<T> from optional<U> uses this function with
     // 'Expr' being of type 'U' and relying on a converting constructor of T from U.
     template<class Expr>
     void construct ( Expr const& expr, void const* )
      {
        new (m_storage.address()) internal_type(expr) ;
        m_initialized = true ;
      }
 
     // Assigns using a form any expression implicitly convertible to the single argument
     // of a T's assignment operator.
     // Converting assignments of optional<T> from optional<U> uses this function with
     // 'Expr' being of type 'U' and relying on a converting assignment of T from U.
     template<class Expr>
     void assign_expr_to_initialized ( Expr const& expr, void const* )
      {
        assign_value(expr, is_reference_predicate());
      }
 
 #endif
 
 #ifdef BOOST_OPTIONAL_WEAK_OVERLOAD_RESOLUTION
     // BCB5.64 (and probably lower versions) workaround.
     //   The in-place factories are supported by means of catch-all constructors
     //   and assignment operators (the functions are parameterized in terms of
     //   an arbitrary 'Expr' type)
     //   This compiler incorrectly resolves the overload set and sinks optional<T> and optional<U>
     //   to the 'Expr'-taking functions even though explicit overloads are present for them.
     //   Thus, the following overload is needed to properly handle the case when the 'lhs'
     //   is another optional.
     //
     // For VC<=70 compilers this workaround doesn't work because the compiler issues and error
     // instead of choosing the wrong overload
     //
 #ifndef  BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
     // Notice that 'Expr' will be optional<T> or optional<U> (but not optional_base<..>)
     template<class Expr>
     void construct ( Expr&& expr, optional_tag const* )
      {
        if ( expr.is_initialized() )
        {
          // An exception can be thrown here.
          // It it happens, THIS will be left uninitialized.
          new (m_storage.address()) internal_type(types::move(expr.get())) ;
          m_initialized = true ;
        }
      }
 #else
     // Notice that 'Expr' will be optional<T> or optional<U> (but not optional_base<..>)
     template<class Expr>
     void construct ( Expr const& expr, optional_tag const* )
      {
        if ( expr.is_initialized() )
        {
          // An exception can be thrown here.
          // It it happens, THIS will be left uninitialized.
          new (m_storage.address()) internal_type(expr.get()) ;
          m_initialized = true ;
        }
      }
 #endif
 #endif // defined BOOST_OPTIONAL_WEAK_OVERLOAD_RESOLUTION
 
     void assign_value ( argument_type val, is_not_reference_tag ) { get_impl() = val; }
     void assign_value ( argument_type val, is_reference_tag     ) { construct(val); }
 #ifndef  BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
     void assign_value ( rval_reference_type val, is_not_reference_tag ) { get_impl() = static_cast<rval_reference_type>(val); }
     void assign_value ( rval_reference_type val, is_reference_tag     ) { construct( static_cast<rval_reference_type>(val) ); }
 #endif
 
     void destroy()
     {
       if ( m_initialized )
         destroy_impl(is_reference_predicate()) ;
     }
 
     reference_const_type get_impl() const { return dereference(get_object(), is_reference_predicate() ) ; }
     reference_type       get_impl()       { return dereference(get_object(), is_reference_predicate() ) ; }
 
     pointer_const_type get_ptr_impl() const { return cast_ptr(get_object(), is_reference_predicate() ) ; }
     pointer_type       get_ptr_impl()       { return cast_ptr(get_object(), is_reference_predicate() ) ; }
 
   private :
 
     // internal_type can be either T or reference_content<T>
 #if defined(BOOST_OPTIONAL_DETAIL_USE_ATTRIBUTE_MAY_ALIAS)
     // This workaround is supposed to silence GCC warnings about broken strict aliasing rules
     internal_type const* get_object() const
     {
         union { void const* ap_pvoid; internal_type const* as_ptype; } caster = { m_storage.address() };
         return caster.as_ptype;
     }
     internal_type *      get_object()
     {
         union { void* ap_pvoid; internal_type* as_ptype; } caster = { m_storage.address() };
         return caster.as_ptype;
     }
 #else
     internal_type const* get_object() const { return static_cast<internal_type const*>(m_storage.address()); }
     internal_type *      get_object()       { return static_cast<internal_type *>     (m_storage.address()); }
 #endif
 
     // reference_content<T> lacks an implicit conversion to T&, so the following is needed to obtain a proper reference.
     reference_const_type dereference( internal_type const* p, is_not_reference_tag ) const { return *p ; }
     reference_type       dereference( internal_type*       p, is_not_reference_tag )       { return *p ; }
     reference_const_type dereference( internal_type const* p, is_reference_tag     ) const { return p->get() ; }
     reference_type       dereference( internal_type*       p, is_reference_tag     )       { return p->get() ; }
 
 #if BOOST_WORKAROUND(BOOST_BORLANDC, BOOST_TESTED_AT(0x581))
     void destroy_impl ( is_not_reference_tag ) { get_ptr_impl()->internal_type::~internal_type() ; m_initialized = false ; }
 #else
     void destroy_impl ( is_not_reference_tag ) { get_ptr_impl()->~T() ; m_initialized = false ; }
 #endif
 
     void destroy_impl ( is_reference_tag     ) { m_initialized = false ; }
 
     // If T is of reference type, trying to get a pointer to the held value must result in a compile-time error.
     // Decent compilers should disallow conversions from reference_content<T>* to T*, but just in case,
     // the following overloads are used to filter out the case and guarantee an error in case of T being a reference.
     pointer_const_type cast_ptr( internal_type const* p, is_not_reference_tag ) const { return p ; }
     pointer_type       cast_ptr( internal_type *      p, is_not_reference_tag )       { return p ; }
     pointer_const_type cast_ptr( internal_type const* p, is_reference_tag     ) const { return &p->get() ; }
     pointer_type       cast_ptr( internal_type *      p, is_reference_tag     )       { return &p->get() ; }
 
     bool m_initialized ;
     storage_type m_storage ;
 } ;
 
 } // namespace optional_detail
 
 template<class T>
 class optional : public optional_detail::optional_base<T>
 {
     typedef optional_detail::optional_base<T> base ;
 
   public :
 
     typedef optional<T> this_type ;
 
     typedef BOOST_DEDUCED_TYPENAME base::value_type           value_type ;
     typedef BOOST_DEDUCED_TYPENAME base::reference_type       reference_type ;
     typedef BOOST_DEDUCED_TYPENAME base::reference_const_type reference_const_type ;
 #ifndef  BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
     typedef BOOST_DEDUCED_TYPENAME base::rval_reference_type  rval_reference_type ;
     typedef BOOST_DEDUCED_TYPENAME base::reference_type_of_temporary_wrapper reference_type_of_temporary_wrapper ;
 #endif
     typedef BOOST_DEDUCED_TYPENAME base::pointer_type         pointer_type ;
     typedef BOOST_DEDUCED_TYPENAME base::pointer_const_type   pointer_const_type ;
     typedef BOOST_DEDUCED_TYPENAME base::argument_type        argument_type ;
 
     // Creates an optional<T> uninitialized.
     // No-throw
     optional() BOOST_NOEXCEPT : base() {}
 
     // Creates an optional<T> uninitialized.
     // No-throw
     optional( none_t none_ ) BOOST_NOEXCEPT : base(none_) {}
 
     // Creates an optional<T> initialized with 'val'.
     // Can throw if T::T(T const&) does
     optional ( argument_type val ) : base(val) {}
 
 #ifndef  BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
     // Creates an optional<T> initialized with 'move(val)'.
     // Can throw if T::T(T &&) does
     optional ( rval_reference_type val ) : base( boost::forward<T>(val) ) 
       {optional_detail::prevent_binding_rvalue_ref_to_optional_lvalue_ref<T, rval_reference_type>();}
 #endif
 
     // Creates an optional<T> initialized with 'val' IFF cond is true, otherwise creates an uninitialized optional.
     // Can throw if T::T(T const&) does
     optional ( bool cond, argument_type val ) : base(cond,val) {}
 
     // NOTE: MSVC needs templated versions first
 
     // Creates a deep copy of another convertible optional<U>
     // Requires a valid conversion from U to T.
     // Can throw if T::T(U const&) does
     template<class U>
     explicit optional ( optional<U> const& rhs )
       :
       base()
     {
       if ( rhs.is_initialized() )
         this->construct(rhs.get());
     }
     
 #ifndef  BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
     // Creates a deep move of another convertible optional<U>
     // Requires a valid conversion from U to T.
     // Can throw if T::T(U&&) does
     template<class U>
     explicit optional ( optional<U> && rhs )
       :
       base()
     {
       if ( rhs.is_initialized() )
         this->construct( boost::move(rhs.get()) );
     }
 #endif
 
 #ifndef BOOST_OPTIONAL_NO_INPLACE_FACTORY_SUPPORT
     // Creates an optional<T> with an expression which can be either
     //  (a) An instance of InPlaceFactory (i.e. in_place(a,b,...,n);
     //  (b) An instance of TypedInPlaceFactory ( i.e. in_place<T>(a,b,...,n);
     //  (c) Any expression implicitly convertible to the single type
     //      of a one-argument T's constructor.
     //  (d*) Weak compilers (BCB) might also resolved Expr as optional<T> and optional<U>
     //       even though explicit overloads are present for these.
     // Depending on the above some T ctor is called.
     // Can throw if the resolved T ctor throws.
 #ifndef BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
 
 
   template<class Expr>
   explicit optional ( Expr&& expr, 
                       BOOST_DEDUCED_TYPENAME boost::disable_if_c<
                         (boost::is_base_of<optional_detail::optional_tag, BOOST_DEDUCED_TYPENAME boost::decay<Expr>::type>::value) || 
                         boost::is_same<BOOST_DEDUCED_TYPENAME boost::decay<Expr>::type, none_t>::value, bool >::type = true 
   ) 
     : base(boost::forward<Expr>(expr),boost::addressof(expr)) 
     {optional_detail::prevent_binding_rvalue_ref_to_optional_lvalue_ref<T, Expr&&>();}
 
 #else
     template<class Expr>
     explicit optional ( Expr const& expr ) : base(expr,boost::addressof(expr)) {}
 #endif // !defined BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
 #endif // !defined BOOST_OPTIONAL_NO_INPLACE_FACTORY_SUPPORT
 
     // Creates a deep copy of another optional<T>
     // Can throw if T::T(T const&) does
     optional ( optional const& rhs ) : base( static_cast<base const&>(rhs) ) {}
 
 #ifndef  BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
     // Creates a deep move of another optional<T>
     // Can throw if T::T(T&&) does
     optional ( optional && rhs )
       BOOST_NOEXCEPT_IF(::boost::is_nothrow_move_constructible<T>::value)
       : base( boost::move(rhs) )
     {}
 
 #endif
    // No-throw (assuming T::~T() doesn't)
     ~optional() {}
 
 #if !defined(BOOST_OPTIONAL_NO_INPLACE_FACTORY_SUPPORT) && !defined(BOOST_OPTIONAL_WEAK_OVERLOAD_RESOLUTION)
     // Assigns from an expression. See corresponding constructor.
     // Basic Guarantee: If the resolved T ctor throws, this is left UNINITIALIZED
 #ifndef  BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
 
     template<class Expr>
     BOOST_DEDUCED_TYPENAME boost::disable_if_c<
       boost::is_base_of<optional_detail::optional_tag, BOOST_DEDUCED_TYPENAME boost::decay<Expr>::type>::value || 
         boost::is_same<BOOST_DEDUCED_TYPENAME boost::decay<Expr>::type, none_t>::value,
       optional&
     >::type 
     operator= ( Expr&& expr )
       {
         optional_detail::prevent_binding_rvalue_ref_to_optional_lvalue_ref<T, Expr&&>();
         this->assign_expr(boost::forward<Expr>(expr),boost::addressof(expr));
         return *this ;
       }
 
 #else
     template<class Expr>
     optional& operator= ( Expr const& expr )
       {
         this->assign_expr(expr,boost::addressof(expr));
         return *this ;
       }
 #endif // !defined  BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
 #endif // !defined(BOOST_OPTIONAL_NO_INPLACE_FACTORY_SUPPORT) && !defined(BOOST_OPTIONAL_WEAK_OVERLOAD_RESOLUTION)
 
     // Copy-assigns from another convertible optional<U> (converts && deep-copies the rhs value)
     // Requires a valid conversion from U to T.
     // Basic Guarantee: If T::T( U const& ) throws, this is left UNINITIALIZED
     template<class U>
     optional& operator= ( optional<U> const& rhs )
       {
         this->assign(rhs);
         return *this ;
       }
       
 #ifndef  BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
     // Move-assigns from another convertible optional<U> (converts && deep-moves the rhs value)
     // Requires a valid conversion from U to T.
     // Basic Guarantee: If T::T( U && ) throws, this is left UNINITIALIZED
     template<class U>
     optional& operator= ( optional<U> && rhs )
       {
         this->assign(boost::move(rhs));
         return *this ;
       }
 #endif
 
     // Assigns from another optional<T> (deep-copies the rhs value)
     // Basic Guarantee: If T::T( T const& ) throws, this is left UNINITIALIZED
     //  (NOTE: On BCB, this operator is not actually called and left is left UNMODIFIED in case of a throw)
     optional& operator= ( optional const& rhs )
       {
         this->assign( static_cast<base const&>(rhs) ) ;
         return *this ;
       }
 
 #ifndef  BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
     // Assigns from another optional<T> (deep-moves the rhs value)
     optional& operator= ( optional && rhs ) 
       BOOST_NOEXCEPT_IF(::boost::is_nothrow_move_constructible<T>::value && ::boost::is_nothrow_move_assignable<T>::value)
       {
         this->assign( static_cast<base &&>(rhs) ) ;
         return *this ;
       }
 #endif
 
     // Assigns from a T (deep-copies the rhs value)
     // Basic Guarantee: If T::( T const& ) throws, this is left UNINITIALIZED
     optional& operator= ( argument_type val )
       {
         this->assign( val ) ;
         return *this ;
       }
 
 #ifndef BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
     // Assigns from a T (deep-moves the rhs value)
     optional& operator= ( rval_reference_type val )
       {
         optional_detail::prevent_binding_rvalue_ref_to_optional_lvalue_ref<T, rval_reference_type>();
         this->assign( boost::move(val) ) ;
         return *this ;
       }
 #endif
 
     // Assigns from a "none"
     // Which destroys the current value, if any, leaving this UNINITIALIZED
     // No-throw (assuming T::~T() doesn't)
     optional& operator= ( none_t none_ ) BOOST_NOEXCEPT
       {
         this->assign( none_ ) ;
         return *this ;
       }
       
 #if (!defined BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES) && (!defined BOOST_NO_CXX11_VARIADIC_TEMPLATES)
     // Constructs in-place
     // upon exception *this is always uninitialized
     template<class... Args>
     void emplace ( Args&&... args )
      {
        this->emplace_assign( boost::forward<Args>(args)... );
      }
 #elif (!defined BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES)
     template<class Arg>
     void emplace ( Arg&& arg )
      {
        this->emplace_assign( boost::forward<Arg>(arg) );
      }
      
     void emplace ()
      {
        this->emplace_assign();
      }
 #else
     template<class Arg>
     void emplace ( const Arg& arg )
      {
        this->emplace_assign( arg );
      }
      
     template<class Arg>
     void emplace ( Arg& arg )
      {
        this->emplace_assign( arg );
      }
      
     void emplace ()
      {
        this->emplace_assign();
      }
 #endif
 
     void swap( optional & arg )
       BOOST_NOEXCEPT_IF(::boost::is_nothrow_move_constructible<T>::value && ::boost::is_nothrow_move_assignable<T>::value)
       {
         // allow for Koenig lookup
         boost::core::invoke_swap(*this, arg);
       }
 
 
     // Returns a reference to the value if this is initialized, otherwise,
     // the behaviour is UNDEFINED
     // No-throw
     reference_const_type get() const { BOOST_ASSERT(this->is_initialized()) ; return this->get_impl(); }
     reference_type       get()       { BOOST_ASSERT(this->is_initialized()) ; return this->get_impl(); }
 
     // Returns a copy of the value if this is initialized, 'v' otherwise
     reference_const_type get_value_or ( reference_const_type v ) const { return this->is_initialized() ? get() : v ; }
     reference_type       get_value_or ( reference_type       v )       { return this->is_initialized() ? get() : v ; }
 
     // Returns a pointer to the value if this is initialized, otherwise,
     // the behaviour is UNDEFINED
     // No-throw
     pointer_const_type operator->() const { BOOST_ASSERT(this->is_initialized()) ; return this->get_ptr_impl() ; }
     pointer_type       operator->()       { BOOST_ASSERT(this->is_initialized()) ; return this->get_ptr_impl() ; }
 
     // Returns a reference to the value if this is initialized, otherwise,
     // the behaviour is UNDEFINED
     // No-throw
 #if (!defined BOOST_NO_CXX11_REF_QUALIFIERS) && (!defined BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES) 
     reference_const_type operator *() const& { return this->get() ; }
     reference_type       operator *() &      { return this->get() ; }
     reference_type_of_temporary_wrapper operator *() && { return base::types::move(this->get()) ; }
 #else
     reference_const_type operator *() const { return this->get() ; }
     reference_type       operator *()       { return this->get() ; }
 #endif // !defined BOOST_NO_CXX11_REF_QUALIFIERS
 
 #if (!defined BOOST_NO_CXX11_REF_QUALIFIERS) && (!defined BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES) 
     reference_const_type value() const&
       { 
         if (this->is_initialized())
           return this->get() ;
         else
           throw_exception(bad_optional_access());
       }
       
     reference_type value() &
       { 
         if (this->is_initialized())
           return this->get() ;
         else
           throw_exception(bad_optional_access());
       }
       
     reference_type_of_temporary_wrapper value() &&
       { 
         if (this->is_initialized())
           return base::types::move(this->get()) ;
         else
           throw_exception(bad_optional_access());
       }
 
 #else 
     reference_const_type value() const
       { 
         if (this->is_initialized())
           return this->get() ;
         else
           throw_exception(bad_optional_access());
       }
       
     reference_type value()
       { 
         if (this->is_initialized())
           return this->get() ;
         else
           throw_exception(bad_optional_access());
       }
 #endif
 
 
 #ifndef BOOST_NO_CXX11_REF_QUALIFIERS
     template <class U>
     value_type value_or ( U&& v ) const&
       { 
         if (this->is_initialized())
           return get();
         else
           return boost::forward<U>(v);
       }
     
     template <class U>
     value_type value_or ( U&& v ) && 
       { 
         if (this->is_initialized())
           return base::types::move(get());
         else
           return boost::forward<U>(v);
       }
 #elif !defined BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
     template <class U>
     value_type value_or ( U&& v ) const 
       {
         if (this->is_initialized())
           return get();
         else
           return boost::forward<U>(v);
       }
 #else
     template <class U>
     value_type value_or ( U const& v ) const 
       { 
         if (this->is_initialized())
           return get();
         else
           return v;
       }
       
     template <class U>
     value_type value_or ( U& v ) const 
       { 
         if (this->is_initialized())
           return get();
         else
           return v;
       }
 #endif
 
 
 #ifndef BOOST_NO_CXX11_REF_QUALIFIERS
     template <typename F>
     value_type value_or_eval ( F f ) const&
       {
         if (this->is_initialized())
           return get();
         else
           return f();
       }
       
     template <typename F>
     value_type value_or_eval ( F f ) &&
       {
         if (this->is_initialized())
           return base::types::move(get());
         else
           return f();
       }
 #else
     template <typename F>
     value_type value_or_eval ( F f ) const
       {
         if (this->is_initialized())
           return get();
         else
           return f();
       }
 #endif
       
     bool operator!() const BOOST_NOEXCEPT { return !this->is_initialized() ; }
     
     BOOST_EXPLICIT_OPERATOR_BOOL_NOEXCEPT()
 } ;
 
 } // namespace boost
 
 
 #endif // header guard

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