operator==, !=, <, <=, >, >=(std::experimental::optional)
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                    < cpp | experimental | optional
                    
                                                            
                    | Defined in header  <experimental/optional> | ||
| Compare two  optionalobjects | ||
| 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  optionalobject with anullopt | ||
| template< class T >  constexpr bool operator==( const optional<T>& opt, std::nullopt_t ); | (7) | (library fundamentals TS) | 
| template< class T >  constexpr bool operator==( std::nullopt_t, const optional<T>& opt ); | (8) | (library fundamentals TS) | 
| template< class T >  constexpr bool operator!=( const optional<T>& opt, std::nullopt_t ); | (9) | (library fundamentals TS) | 
| template< class T >  constexpr bool operator!=( std::nullopt_t, const optional<T>& opt ); | (10) | (library fundamentals TS) | 
| template< class T >  constexpr bool operator<( const optional<T>& opt, std::nullopt_t ); | (11) | (library fundamentals TS) | 
| template< class T >  constexpr bool operator<( std::nullopt_t, const optional<T>& opt ); | (12) | (library fundamentals TS) | 
| template< class T >  constexpr bool operator<=( const optional<T>& opt, std::nullopt_t ); | (13) | (library fundamentals TS) | 
| template< class T >  constexpr bool operator<=( std::nullopt_t, const optional<T>& opt); | (14) | (library fundamentals TS) | 
| template< class T >  constexpr bool operator>( const optional<T>& opt, std::nullopt_t ); | (15) | (library fundamentals TS) | 
| template< class T >  constexpr bool operator>( std::nullopt_t, const optional<T>& opt ); | (16) | (library fundamentals TS) | 
| template< class T >  constexpr bool operator>=( const optional<T>& opt, std::nullopt_t ); | (17) | (library fundamentals TS) | 
| template< class T >  constexpr bool operator>=( std::nullopt_t, const optional<T>& opt ); | (18) | (library fundamentals TS) | 
| Compare an  optionalobject with aT | ||
| 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 ); | (39) | (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, - lhsis considered equal to- rhsif, and only if, both- lhsand- rhsdo not contain a value.
- lhsis considered less than- rhsif, and only if,- rhscontains a value and- lhsdoes 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 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 optionalobject to compare | 
| value | - | value to compare to the contained value | 
| Type requirements | ||
| - Tmust meet the requirements ofEqualityComparablein 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.
2) Returns !(lhs == rhs)
3) If bool(rhs) == false returns false
 Otherwise, if bool(lhs) == false, returns true
 Otherwise returns *x < *y
4) Returns !(rhs < lhs)
5) Returns rhs < lhs
6) 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 !(opt > value).
26) Returns !(value > opt).
27) Returns bool(opt) ? value < *opt  : false.
28) Returns bool(opt) ? *opt < value  : true.
29) Returns !(opt < value).
30) Returns !(value < opt).
[edit] Exceptions
1-6) (none)
7-18) 
noexcept specification:  
noexcept
  19-30) (none)


