operator==, !=, <, <=, >, >=(std::experimental::optional) (original) (raw)

Defined in header <experimental/optional>
Compare two optional objects
template< class T > constexpr bool operator==( const optional<T>& lhs, const optional<T>& rhs ); (1) (library fundamentals TS)
template< class T > constexpr bool operator!=( const optional<T>& lhs, const optional<T>& rhs ); (2) (library fundamentals TS)
template< class T > constexpr bool operator<( const optional<T>& lhs, const optional<T>& rhs ); (3) (library fundamentals TS)
template< class T > constexpr bool operator<=( const optional<T>& lhs, const optional<T>& rhs ); (4) (library fundamentals TS)
template< class T > constexpr bool operator>( const optional<T>& lhs, const optional<T>& rhs ); (5) (library fundamentals TS)
template< class T > constexpr bool operator>=( const optional<T>& lhs, const optional<T>& rhs ); (6) (library fundamentals TS)
Compare an optional object with a nullopt
template< class T > constexpr bool operator==( const optional<T>& opt, std::nullopt_t ) noexcept; (7) (library fundamentals TS)
template< class T > constexpr bool operator==( std::nullopt_t, const optional<T>& opt ) noexcept; (8) (library fundamentals TS)
template< class T > constexpr bool operator!=( const optional<T>& opt, std::nullopt_t ) noexcept; (9) (library fundamentals TS)
template< class T > constexpr bool operator!=( std::nullopt_t, const optional<T>& opt ) noexcept; (10) (library fundamentals TS)
template< class T > constexpr bool operator<( const optional<T>& opt, std::nullopt_t ) noexcept; (11) (library fundamentals TS)
template< class T > constexpr bool operator<( std::nullopt_t, const optional<T>& opt ) noexcept; (12) (library fundamentals TS)
template< class T > constexpr bool operator<=( const optional<T>& opt, std::nullopt_t ) noexcept; (13) (library fundamentals TS)
template< class T > constexpr bool operator<=( std::nullopt_t, const optional<T>& opt ) noexcept; (14) (library fundamentals TS)
template< class T > constexpr bool operator>( const optional<T>& opt, std::nullopt_t ) noexcept; (15) (library fundamentals TS)
template< class T > constexpr bool operator>( std::nullopt_t, const optional<T>& opt ) noexcept; (16) (library fundamentals TS)
template< class T > constexpr bool operator>=( const optional<T>& opt, std::nullopt_t ) noexcept; (17) (library fundamentals TS)
template< class T > constexpr bool operator>=( std::nullopt_t, const optional<T>& opt ) noexcept; (18) (library fundamentals TS)
Compare an optional object with a T
template< class T > constexpr bool operator==( const optional<T>& opt, const T& value ); (19) (library fundamentals TS)
template< class T > constexpr bool operator==( const T& value, const optional<T>& opt ); (20) (library fundamentals TS)
template< class T > constexpr bool operator!=( const optional<T>& opt, const T& value ); (21) (library fundamentals TS)
template< class T > constexpr bool operator!=( const T& value, const optional<T>& opt ); (22) (library fundamentals TS)
template< class T > constexpr bool operator<( const optional<T>& opt, const T& value ); (23) (library fundamentals TS)
template< class T > constexpr bool operator<( const T& value, const optional<T>& opt ); (24) (library fundamentals TS)
template< class T > constexpr bool operator<=( const optional<T>& opt, const T& value ); (25) (library fundamentals TS)
template< class T > constexpr bool operator<=( const T& value, const optional<T>& opt ); (26) (library fundamentals TS)
template< class T > constexpr bool operator>( const optional<T>& opt, const T& value ); (27) (library fundamentals TS)
template< class T > constexpr bool operator>( const T& value, const optional<T>& opt ); (28) (library fundamentals TS)
template< class T > constexpr bool operator>=( const optional<T>& opt, const T& value ); (29) (library fundamentals TS)
template< class T > constexpr bool operator>=( const T& value, const optional<T>& opt ); (30) (library fundamentals TS)

Performs comparison operations on optional objects.

1-6) Compares two optional objects, lhs and rhs. The contained values are compared (using operator== for (1,2) and operator< for (3-6)) only if both lhs and rhs contain values. Otherwise,

7-18) Compares opt with a nullopt. Equivalent to (1-6) when comparing to an optional that does not contain a value.

19-30) Compares opt with a value. The values are compared (using operator== for (19-22) and operator< for (23-30)) only if opt contains a value. Otherwise, opt is considered less than value.

[edit] Parameters

lhs, rhs, opt - an optional object to compare
value - value to compare to the contained value
Type requirements
-T must meet the requirements of EqualityComparable in order to use overloads (1,2).

[edit] Return value

  1. If bool(lhs) != bool(rhs), returns false.

Otherwise, if bool(lhs) == false (and so bool(rhs) == false as well), returns true.

Otherwise, returns *lhs == *rhs.

  1. Returns !(lhs == rhs).

  2. If bool(rhs) == false returns false.

Otherwise, if bool(lhs) == false, returns true.

Otherwise returns *x < *y.

  1. Returns !(rhs < lhs).

  2. Returns rhs < lhs.

  3. Returns !(lhs < rhs).

7,8) Returns !opt.

9,10) Returns bool(opt).

  1. Returns false.

  2. Returns bool(opt).

  3. Returns !opt.

  4. Returns true.

  5. Returns bool(opt).

  6. Returns false.

  7. Returns true.

  8. Returns !opt.

  9. Returns bool(opt) ? *opt == value : false.

  10. Returns bool(opt) ? value == *opt : false.

  11. Returns bool(opt) ? !(*opt == value) : true.

  12. Returns bool(opt) ? !(value == *opt) : true.

  13. Returns bool(opt) ? *opt < value : true.

  14. Returns bool(opt) ? value < *opt : false.

  15. Returns !(opt > value).

  16. Returns !(value > opt).

  17. Returns bool(opt) ? value < *opt : false.

  18. Returns bool(opt) ? *opt < value : true.

  19. Returns !(opt < value).

  20. Returns !(value < opt).

[edit] Exceptions

1-6) (none)

19-30) (none)