// 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