// Copyright (C) 2003, Fernando Luis Cacciola Carballal.

//

// 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/lib/optional for documentation.

//

// You are welcome to contact the author at:

//  fernando_cacciola@hotmail.com

//

#ifndef BOOST_OPTIONAL_OPTIONAL_FLC_19NOV2002_HPP

#define BOOST_OPTIONAL_OPTIONAL_FLC_19NOV2002_HPP

#include<new>

#include<algorithm>

#include "boost/config.hpp"

#include "boost/assert.hpp"

#include "boost/type.hpp"

#include "boost/type_traits/alignment_of.hpp"

#include "boost/type_traits/type_with_alignment.hpp"

#include "boost/type_traits/remove_reference.hpp"

#include "boost/type_traits/is_reference.hpp"

#include "boost/mpl/if.hpp"

#include "boost/mpl/bool.hpp"

#include "boost/mpl/not.hpp"

#include "boost/detail/reference_content.hpp"

#include "boost/none.hpp"

#include "boost/utility/compare_pointees.hpp"

#include "boost/optional/optional_fwd.hpp"

#if BOOST_WORKAROUND(BOOST_MSVC, == 1200)

// VC6.0 has the following bug:

//   When a templated assignment operator exist, an implicit conversion

//   constructing an optional<T> is used when assigment of the form:

//     optional<T> opt ; opt = T(...);

//   is compiled.

//   However, optional's ctor is _explicit_ and the assignemt shouldn't compile.

//   Therefore, for VC6.0 templated assignment is disabled.

//

#define BOOST_OPTIONAL_NO_CONVERTING_ASSIGNMENT

#endif

#if BOOST_WORKAROUND(BOOST_MSVC, == 1300)

// VC7.0 has the following bug:

//   When both a non-template and a template copy-ctor exist

//   and the templated version is made 'explicit', the explicit is also

//   given to the non-templated version, making the class non-implicitely-copyable.

//

#define BOOST_OPTIONAL_NO_CONVERTING_COPY_CTOR

#endif

#if BOOST_WORKAROUND(BOOST_MSVC, <= 1300) || BOOST_WORKAROUND(BOOST_INTEL_CXX_VERSION,<=700)

// AFAICT only VC7.1 correctly resolves the overload set

// that includes the in-place factory taking functions,

// so for the other VC versions, in-place factory support

// is disabled

#define BOOST_OPTIONAL_NO_INPLACE_FACTORY_SUPPORT

#endif

#if BOOST_WORKAROUND(__BORLANDC__, <= 0x551)

// BCB (5.5.1) cannot parse the nested template struct in an inplace factory.

#define BOOST_OPTIONAL_NO_INPLACE_FACTORY_SUPPORT

#endif

#if !defined(BOOST_OPTIONAL_NO_INPLACE_FACTORY_SUPPORT) \

    && BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x581) )

// BCB (up to 5.64) has the following bug:

//   If there is a member function/operator template of the form

//     template<class Expr> mfunc( Expr expr ) ;

//   some calls are resolved to this even if there are other better matches.

//   The effect of this bug is that calls to converting ctors and assignments

//   are incrorrectly sink to this general catch-all member function template as shown above.

#define BOOST_OPTIONAL_WEAK_OVERLOAD_RESOLUTION

#endif

// Daniel Wallin discovered that bind/apply.hpp badly interacts with the apply<>

// member template of a factory as used in the optional<> implementation.

// He proposed this simple fix which is to move the call to apply<> outside

// namespace boost.

namespace boost_optional_detail

{

  template <class T, class Factory>

  void construct(Factory const& factory, void* address)

  {

    factory.BOOST_NESTED_TEMPLATE apply<T>(address);

  }

}

namespace boost {

class in_place_factory_base ;

class typed_in_place_factory_base ;

namespace optional_detail {

// This local class is used instead of that in "aligned_storage.hpp"

// because I've found the 'official' class to ICE BCB5.5

// when some types are used with optional<>

// (due to sizeof() passed down as a non-type template parameter)

template <class T>

class aligned_storage

{

    // Borland ICEs if unnamed unions are used for this!

    union dummy_u

    {

        char data[ sizeof(T) ];

        BOOST_DEDUCED_TYPENAME type_with_alignment<

          ::boost::alignment_of<T>::value >::type aligner_;

    } dummy_ ;

  public:

    void const* address() const { return &dummy_.data[0]; }

    void      * address()       { return &dummy_.data[0]; }

} ;

template<class T>

struct types_when_isnt_ref

{

  typedef T const& reference_const_type ;

  typedef T &      reference_type ;

  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 ;

  typedef raw_type* pointer_const_type ;

  typedef raw_type* pointer_type ;

  typedef raw_type& argument_type ;

} ;

struct optional_tag {} ;

template<class T>

class optional_base : public optional_tag

{

  private :

    typedef

#if !BOOST_WORKAROUND(__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 mpl::true_  is_reference_tag ;

    typedef mpl::false_ is_not_reference_tag ;

    typedef BOOST_DEDUCED_TYPENAME is_reference<T>::type is_reference_predicate ;

    typedef BOOST_DEDUCED_TYPENAME mpl::if_<is_reference_predicate,types_when_ref,types_when_not_ref>::type types ;

    typedef bool (this_type::*unspecified_bool_type)() const;

    typedef BOOST_DEDUCED_TYPENAME types::reference_type       reference_type ;

    typedef BOOST_DEDUCED_TYPENAME types::reference_const_type reference_const_type ;

    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);

    }

    // Creates an optional<T> initialized with 'val' IFF cond is true, otherwise creates an uninitialzed 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());

    }

    // 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);

    }

    // 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());

      }

    }

    // 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() )

             assign_value(static_cast<value_type>(rhs.get()), is_reference_predicate() );

        else destroy();

      }

      else

      {

        if ( rhs.is_initialized() )

          construct(static_cast<value_type>(rhs.get()));

      }

    }

    // 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);

    }

    // Assigns from "none", destroying the current value, if any, leaving this UNINITIALIZED

    // No-throw (assuming T::~T() doesn't)

    void assign ( none_t ) { destroy(); }

#ifndef BOOST_OPTIONAL_NO_INPLACE_FACTORY_SUPPORT

    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

  public :

    // Destroys the current value, if any, leaving this UNINITIALIZED

    // No-throw (assuming T::~T() doesn't)

    void reset() { destroy(); }

    // 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_NO_INPLACE_FACTORY_SUPPORT

    // Constructs in-place using the given factory

    template<class Expr>

    void construct ( Expr const& factory, in_place_factory_base const* )

     {

       BOOST_STATIC_ASSERT ( ::boost::mpl::not_<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 ( ::boost::mpl::not_<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

    // Constructs using any expression implicitely 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 implicitely 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());

     }

#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 dosen't work becasue the comnpiler issues and error

    // instead of choosing the wrong overload

    //

    // 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

    void assign_value ( argument_type val, is_not_reference_tag ) { get_impl() = val; }

    void assign_value ( argument_type val, is_reference_tag     ) { construct(val); }

    void destroy()

    {

      if ( m_initialized )

        destroy_impl(is_reference_predicate()) ;

    }

    unspecified_bool_type safe_bool() const { return m_initialized ? &this_type::is_initialized : 0 ; }

    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>

    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()); }

    // 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(__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::~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 olverloads 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 ;

    typedef BOOST_DEDUCED_TYPENAME base::unspecified_bool_type  unspecified_bool_type ;

  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 ;

    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() : base() {}

    // Creates an optional<T> uninitialized.

    // No-throw

    optional( none_t none_ ) : base(none_) {}

    // Creates an optional<T> initialized with 'val'.

    // Can throw if T::T(T const&) does

    optional ( argument_type val ) : base(val) {}

    // 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) {}

#ifndef BOOST_OPTIONAL_NO_CONVERTING_COPY_CTOR

    // 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());

    }

#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 implicitely 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 is the resolved T ctor throws.

    template<class Expr>

    explicit optional ( Expr const& expr ) : base(expr,&expr) {}

#endif

    // Creates a deep copy of another optional<T>

    // Can throw if T::T(T const&) does

    optional ( optional const& rhs ) : base(rhs) {}

   // 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

    template<class Expr>

    optional& operator= ( Expr expr )

      {

        this->assign_expr(expr,&expr);

        return *this ;

      }

#endif

#ifndef BOOST_OPTIONAL_NO_CONVERTING_ASSIGNMENT

    // 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 ;

      }

#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( rhs ) ;

        return *this ;

      }

    // 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 ;

      }

    // 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_ )

      {

        this->assign( none_ ) ;

        return *this ;

      }

    // 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

    reference_const_type operator *() const { return this->get() ; }

    reference_type       operator *()       { return this->get() ; }

    // implicit conversion to "bool"

    // No-throw

    operator unspecified_bool_type() const { return this->safe_bool() ; }

       // This is provided for those compilers which don't like the conversion to bool

       // on some contexts.

       bool operator!() const { return !this->is_initialized() ; }

} ;

// Returns optional<T>(v)

template<class T> 

inline 

optional<T> make_optional ( T const& v  )

{

  return optional<T>(v);

}

// Returns optional<T>(cond,v)

template<class T> 

inline 

optional<T> make_optional ( bool cond, T const& v )

{

  return optional<T>(cond,v);

}

// Returns a reference to the value if this is initialized, otherwise, the behaviour is UNDEFINED.

// No-throw

template<class T>

inline

BOOST_DEDUCED_TYPENAME optional<T>::reference_const_type

get ( optional<T> const& opt )

{

  return opt.get() ;

}

template<class T>

inline

BOOST_DEDUCED_TYPENAME optional<T>::reference_type

get ( optional<T>& opt )

{

  return opt.get() ;

}

// Returns a pointer to the value if this is initialized, otherwise, returns NULL.

// No-throw

template<class T>

inline

BOOST_DEDUCED_TYPENAME optional<T>::pointer_const_type

get ( optional<T> const* opt )

{

  return opt->get_ptr() ;

}

template<class T>

inline

BOOST_DEDUCED_TYPENAME optional<T>::pointer_type

get ( optional<T>* opt )

{

  return opt->get_ptr() ;

}

// Returns a reference to the value if this is initialized, otherwise, the behaviour is UNDEFINED.

// No-throw

template<class T>

inline

BOOST_DEDUCED_TYPENAME optional<T>::reference_const_type

get_optional_value_or ( optional<T> const& opt, BOOST_DEDUCED_TYPENAME optional<T>::reference_const_type v )

{

  return opt.get_value_or(v) ;

}

template<class T>

inline

BOOST_DEDUCED_TYPENAME optional<T>::reference_type

get_optional_value_or ( optional<T>& opt, BOOST_DEDUCED_TYPENAME optional<T>::reference_type v )

{

  return opt.get_value_or(v) ;

}

// Returns a pointer to the value if this is initialized, otherwise, returns NULL.

// No-throw

template<class T>

inline

BOOST_DEDUCED_TYPENAME optional<T>::pointer_const_type

get_pointer ( optional<T> const& opt )

{

  return opt.get_ptr() ;

}

template<class T>

inline

BOOST_DEDUCED_TYPENAME optional<T>::pointer_type

get_pointer ( optional<T>& opt )

{

  return opt.get_ptr() ;

}

// optional's relational operators ( ==, !=, <, >, <=, >= ) have deep-semantics (compare values).

// WARNING: This is UNLIKE pointers. Use equal_pointees()/less_pointess() in generic code instead.

//

// optional<T> vs optional<T> cases

//

template<class T>

inline

bool operator == ( optional<T> const& x, optional<T> const& y )

{ return equal_pointees(x,y); }

template<class T>

inline

bool operator < ( optional<T> const& x, optional<T> const& y )

{ return less_pointees(x,y); }

template<class T>

inline

bool operator != ( optional<T> const& x, optional<T> const& y )

{ return !( x == y ) ; }

template<class T>

inline

bool operator > ( optional<T> const& x, optional<T> const& y )

{ return y < x ; }

template<class T>

inline

bool operator <= ( optional<T> const& x, optional<T> const& y )

{ return !( y < x ) ; }

template<class T>

inline

bool operator >= ( optional<T> const& x, optional<T> const& y )

{ return !( x < y ) ; }

//

// optional<T> vs T cases

//

template<class T>

inline

bool operator == ( optional<T> const& x, T const& y )

{ return equal_pointees(x, optional<T>(y)); }

template<class T>

inline

bool operator < ( optional<T> const& x, T const& y )

{ return less_pointees(x, optional<T>(y)); }

template<class T>

inline

bool operator != ( optional<T> const& x, T const& y )

{ return !( x == y ) ; }

template<class T>

inline

bool operator > ( optional<T> const& x, T const& y )

{ return y < x ; }

template<class T>

inline

bool operator <= ( optional<T> const& x, T const& y )

{ return !( y < x ) ; }

template<class T>

inline

bool operator >= ( optional<T> const& x, T const& y )

{ return !( x < y ) ; }

//

// T vs optional<T> cases

//

template<class T>

inline

bool operator == ( T const& x, optional<T> const& y )

{ return equal_pointees( optional<T>(x), y ); }

template<class T>

inline

bool operator < ( T const& x, optional<T> const& y )

{ return less_pointees( optional<T>(x), y ); }

template<class T>

inline

bool operator != ( T const& x, optional<T> const& y )

{ return !( x == y ) ; }

template<class T>

inline

bool operator > ( T const& x, optional<T> const& y )

{ return y < x ; }

template<class T>

inline

bool operator <= ( T const& x, optional<T> const& y )

{ return !( y < x ) ; }

template<class T>

inline

bool operator >= ( T const& x, optional<T> const& y )

{ return !( x < y ) ; }

//

// optional<T> vs none cases

//

template<class T>

inline

bool operator == ( optional<T> const& x, none_t )

{ return equal_pointees(x, optional<T>() ); }

template<class T>

inline

bool operator < ( optional<T> const& x, none_t )

{ return less_pointees(x,optional<T>() ); }

template<class T>

inline

bool operator != ( optional<T> const& x, none_t y )

{ return !( x == y ) ; }

template<class T>

inline

bool operator > ( optional<T> const& x, none_t y )

{ return y < x ; }

template<class T>

inline

bool operator <= ( optional<T> const& x, none_t y )

{ return !( y < x ) ; }

template<class T>

inline

bool operator >= ( optional<T> const& x, none_t y )

{ return !( x < y ) ; }

//

// none vs optional<T> cases

//

template<class T>

inline

bool operator == ( none_t x, optional<T> const& y )

{ return equal_pointees(optional<T>() ,y); }

template<class T>

inline

bool operator < ( none_t x, optional<T> const& y )

{ return less_pointees(optional<T>() ,y); }

template<class T>

inline

bool operator != ( none_t x, optional<T> const& y )

{ return !( x == y ) ; }

template<class T>

inline

bool operator > ( none_t x, optional<T> const& y )

{ return y < x ; }

template<class T>

inline

bool operator <= ( none_t x, optional<T> const& y )

{ return !( y < x ) ; }

template<class T>

inline

bool operator >= ( none_t x, optional<T> const& y )

{ return !( x < y ) ; }

//

// The following swap implementation follows the GCC workaround as found in

//  "boost/detail/compressed_pair.hpp"

//

namespace optional_detail {

// GCC < 3.2 gets the using declaration at namespace scope (FLC, DWA)

#if BOOST_WORKAROUND(__GNUC__, < 3)                             \

    || BOOST_WORKAROUND(__GNUC__, == 3) && __GNUC_MINOR__ <= 2

   using std::swap;

#define BOOST_OPTIONAL_STD_SWAP_INTRODUCED_AT_NS_SCOPE

#endif

// optional's swap:

// If both are initialized, calls swap(T&, T&). If this swap throws, both will remain initialized but their values are now unspecified.

// If only one is initialized, calls U.reset(*I), THEN I.reset().

// If U.reset(*I) throws, both are left UNCHANGED (U is kept uinitialized and I is never reset)

// If both are uninitialized, do nothing (no-throw)

template<class T>

inline

void optional_swap ( optional<T>& x, optional<T>& y )

{

  if ( !x && !!y )

  {

    x.reset(*y);

    y.reset();

  }

  else if ( !!x && !y )

  {

    y.reset(*x);

    x.reset();

  }

  else if ( !!x && !!y )

  {

// GCC > 3.2 and all other compilers have the using declaration at function scope (FLC)

#ifndef BOOST_OPTIONAL_STD_SWAP_INTRODUCED_AT_NS_SCOPE

    // allow for Koenig lookup

    using std::swap ;

#endif

    swap(*x,*y);

  }

}

} // namespace optional_detail

template<class T> inline void swap ( optional<T>& x, optional<T>& y )

{

  optional_detail::optional_swap(x,y);

}

} // namespace boost

#endif