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Difference between revisions of "cpp/utility/variant/operator cmp"

From cppreference.com
< cpp‎ | utility‎ | variant
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template <class... Types>
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template< class... Types >
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constexpr bool operator==(const std::variant<Types...>& v, const std::variant<Types...>& w);
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constexpr bool operator==( const std::variant<Types...>& v,  
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                          const std::variant<Types...>& w );
 
}}
 
}}
 
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template <class... Types>
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template< class... Types >
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constexpr bool operator!=(const std::variant<Types...>& v, const std::variant<Types...>& w);
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constexpr bool operator!=( const std::variant<Types...>& v,
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                          const std::variant<Types...>& w );
 
}}
 
}}
 
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template <class... Types>
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template< class... Types >
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constexpr bool operator<(const std::variant<Types...>& v, const std::variant<Types...>& w);
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constexpr bool operator<( const std::variant<Types...>& v,  
 +
                          const std::variant<Types...>& w );
 
}}
 
}}
 
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template <class... Types>
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template< class... Types >
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constexpr bool operator>(const std::variant<Types...>& v, const std::variant<Types...>& w);
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constexpr bool operator>( const std::variant<Types...>& v,
 +
                          const std::variant<Types...>& w );
 
}}
 
}}
 
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{{dcl | since=c++17 | num=5 |1=
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template <class... Types>
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template< class... Types >
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constexpr bool operator<=(const std::variant<Types...>& v, const std::variant<Types...>& w);
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constexpr bool operator<=( const std::variant<Types...>& v,
 +
                          const std::variant<Types...>& w );
 
}}
 
}}
 
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{{dcl | since=c++17 | num=6 |1=
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template <class... Types>
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template< class... Types >
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constexpr bool operator>=(const std::variant<Types...>& v, const std::variant<Types...>& w);
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constexpr bool operator>=( const std::variant<Types...>& v,  
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                          const std::variant<Types...>& w );
 
}}
 
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Revision as of 15:11, 29 October 2019

 
C++
 
Utilities library
General utilities
Relational operators (deprecated in C++20)
 
std::variant
 
Defined in header <variant>
template< class... Types >

constexpr bool operator==( const std::variant<Types...>& v,

                           const std::variant<Types...>& w );
 (1) (since C++17)
template< class... Types >

constexpr bool operator!=( const std::variant<Types...>& v,

                           const std::variant<Types...>& w );
 (2) (since C++17)
template< class... Types >

constexpr bool operator<( const std::variant<Types...>& v,

                          const std::variant<Types...>& w );
 (3) (since C++17)
template< class... Types >

constexpr bool operator>( const std::variant<Types...>& v,

                          const std::variant<Types...>& w );
 (4) (since C++17)
template< class... Types >

constexpr bool operator<=( const std::variant<Types...>& v,

                           const std::variant<Types...>& w );
 (5) (since C++17)
template< class... Types >

constexpr bool operator>=( const std::variant<Types...>& v,

                           const std::variant<Types...>& w );
 (6) (since C++17)
1) Equality operator for variants:
  • If v.index() != w.index(), returns false;
  • otherwise if v.valueless_by_exception(), returns true;
  • otherwise returns std::get<v.index()>(v) == std::get<v.index()>(w). The behavior is undefined if std::get<i>(v) == std::get<i>(w) is not a valid expression returning a type convertible to bool, for any i.
2) Inequality operator for variants:
  • If v.index() != w.index(), returns true;
  • otherwise if v.valueless_by_exception(), returns false;
  • otherwise returns std::get<v.index()>(v) != std::get<v.index()>(w). The behavior is undefined if std::get<i>(v) != std::get<i>(w) is not a valid expression returning a type convertible to bool, for any i.
3) Less-than operator for variants:
  • If w.valueless_by_exception(), returns false;
  • otherwise if v.valueless_by_exception(), returns true;
  • otherwise if v.index() < w.index(), returns true;
  • otherwise if v.index() > w.index(), returns false;
  • otherwise returns std::get<v.index()>(v) < std::get<v.index()>(w). The behavior is undefined if std::get<i>(v) < std::get<i>(w) is not a valid expression returning a type convertible to bool, for any i.
4) Greater-than operator for variants:
  • If v.valueless_by_exception(), returns false;
  • otherwise if w.valueless_by_exception(), returns true;
  • otherwise if v.index() > w.index(), returns true;
  • otherwise if v.index() < w.index(), returns false;
  • otherwise returns std::get<v.index()>(v) > std::get<v.index()>(w). The behavior is undefined if std::get<i>(v) > std::get<i>(w) is not a valid expression returning a type convertible to bool, for any i.
5) Less-equal operator for variants:
  • If v.valueless_by_exception(), returns true;
  • otherwise if w.valueless_by_exception(), returns false;
  • otherwise if v.index() < w.index(), returns true;
  • otherwise if v.index() > w.index(), returns false;
  • otherwise returns std::get<v.index()>(v) <= std::get<v.index()>(w). The behavior is undefined if std::get<i>(v) <= std::get<i>(w) is not a valid expression returning a type convertible to bool, for any i.
6) Greater-equal operator for variants:
  • If w.valueless_by_exception(), returns true;
  • otherwise if v.valueless_by_exception(), returns false;
  • otherwise if v.index() > w.index(), returns true;
  • otherwise if v.index() < w.index(), returns false;
  • otherwise std::get<v.index()>(v) >= std::get<v.index()>(w). The behavior is undefined if std::get<i>(v) >= std::get<i>(w) is not a valid expression returning a type convertible to bool, for any i.

Contents

Parameters

v,w - variants to compare

Return value

The boolean result of the comparison as described above.

Example

This section is incomplete
Reason: no example

See also

(C++17)(C++17)(C++17)(C++17)(C++17)(C++17)(C++20)
 compares optional objects
(function template) [edit]
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