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operator==, !=, <, <=, >, >=(std::optional)

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

Performs comparison operations on optional objects.

1-6) Compares two optional objects, lhs and rhs. The contained values are compared (using the corresponding operator of T) only if both lhs and rhs contain values. Otherwise,

lhs is considered equal to rhs if, and only if, both lhs and rhs do not contain a value.
lhs is considered less than rhs if, and only if, rhs contains a value and lhs does not.

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 the corresponding operator of T) only if opt contains a value. Otherwise, opt is considered less than value.

Parameters

lhs, rhs, opt	-	an `optional` object to compare
value	-	value to compare to the contained value

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.

2) If bool(lhs) != bool(rhs), returns true

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

3) If bool(rhs) == false returns false

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

4) If bool(lhs) == false returns true

Otherwise, if bool(rhs) == false, returns false
Otherwise returns *lhs <= *rhs.

5) If bool(lhs) == false returns false

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

6) If bool(rhs) == false returns true

Otherwise, if bool(lhs) == false, returns false
Otherwise returns *lhs >= *rhs.

7-8) Returns !opt.

9-10) Returns bool(opt).

11) Returns false.

12) Returns bool(opt).

13) Returns !opt.

14) Returns true.

15) Returns bool(opt).

16) Returns false.

17) Returns true.

18) Returns !opt.

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

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

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

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

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

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

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

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

27) Returns bool(opt) ? *opt > value : false.

28) Returns bool(opt) ? value > *opt : true.

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

30) Returns bool(opt) ? value >= *opt : true.

Exceptions

1-6) (none)

7-18)

noexcept specification:

noexcept

19-30) (none)

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