Boost C++ Libraries

namespace boost {

template<class T>
class optional
{
    public :

    // (If T is of reference type, the parameters and results by reference are by value)

    optional () ; 

    optional ( none_t ) ; 

    optional ( T const& v ) ; 

    // [new in 1.34]
    optional ( bool condition, T const& v ) ;  

    optional ( optional const& rhs ) ; 

    template<class U> explicit optional ( optional<U> const& rhs ) ; 

    template<class InPlaceFactory> explicit optional ( InPlaceFactory const& f ) ; 

    template<class TypedInPlaceFactory> explicit optional ( TypedInPlaceFactory const& f ) ; 

    optional& operator = ( none_t ) ; 

    optional& operator = ( T const& v ) ; 

    optional& operator = ( optional const& rhs ) ; 

    template<class U> optional& operator = ( optional<U> const& rhs ) ; 

    template<class InPlaceFactory> optional& operator = ( InPlaceFactory const& f ) ; 

    template<class TypedInPlaceFactory> optional& operator = ( TypedInPlaceFactory const& f ) ; 

    T const& get() const ; 
    T&       get() ; 

    // [new in 1.34]
    T const& get_value_or( T const& default ) const ;  

    T const* operator ->() const ; 
    T*       operator ->() ; 

    T const& operator *() const ; 
    T&       operator *() ; 

    T const* get_ptr() const ; 
    T*       get_ptr() ; 

    operator unspecified-bool-type() const ; 

    bool operator!() const ; 

    // deprecated methods

    // (deprecated)
    void reset() ; 

    // (deprecated)
    void reset ( T const& ) ; 

    // (deprecated)
    bool is_initialized() const ; 

};

template<class T> inline bool operator == ( optional<T> const& x, optional<T> const& y ) ; 

template<class T> inline bool operator != ( optional<T> const& x, optional<T> const& y ) ; 

template<class T> inline bool operator <  ( optional<T> const& x, optional<T> const& y ) ; 

template<class T> inline bool operator >  ( optional<T> const& x, optional<T> const& y ) ; 

template<class T> inline bool operator <= ( optional<T> const& x, optional<T> const& y ) ; 

template<class T> inline bool operator >= ( optional<T> const& x, optional<T> const& y ) ; 

// [new in 1.34]
template<class T> inline optional<T> make_optional ( T const& v ) ; 

// [new in 1.34]
template<class T> inline optional<T> make_optional ( bool condition, T const& v ) ; 

// [new in 1.34]
template<class T> inline T const& get_optional_value_or ( optional<T> const& opt, T const& default ) ;  

template<class T> inline T const& get ( optional<T> const& opt ) ; 

template<class T> inline T& get ( optional<T> & opt ) ; 

template<class T> inline T const* get ( optional<T> const* opt ) ; 

template<class T> inline T* get ( optional<T>* opt ) ; 

template<class T> inline T const* get_pointer ( optional<T> const& opt ) ; 

template<class T> inline T* get_pointer ( optional<T> & opt ) ; 

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

} // namespace boost