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

 

C++

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Language support library

Concepts library (C++20)

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Utilities library

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Technical Specifications

 

Utilities library

Type support (basic types, RTTI, type traits)
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Formatting library (C++20)
initializer_list (C++11)
source_location (C++20)
bitset
hash (C++11)
integer_sequence (C++14)
Relational operators (deprecated in C++20)
rel_ops::operator!=rel_ops::operator>rel_ops::operator<=rel_ops::operator>=
Comparisons (C++20)
three_way_comparablethree_way_comparable_with
strong_ordering weak_ordering partial_ordering common_comparison_category compare_three_way_result compare_three_way	strong_order weak_order partial_order compare_strong_order_fallback compare_weak_order_fallback compare_partial_order_fallback	is_eqis_neqis_ltis_lteqis_gtis_gteq
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pair tuple (C++11) apply (C++17) make_from_tuple (C++17)	optional (C++17) any (C++17) variant (C++17)
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swap
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declval (C++11)
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launder (C++17)

 

std::variant

Member functions

variant::variant

variant::~variant

variant::operator=

Observers

variant::index

variant::valueless_by_exception

Modifiers

variant::emplace

variant::swap

Non-member functions

visit

holds_alternative

get

get_if

operator==operator!=operator<operator<=operator>operator>=operator<=> (C++20)

swap

Helper classes

monostate

bad_variant_access

variant_size

variant_alternative

hash

Helper objects

variant_npos

 

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)
template< class... Types > constexpr std::common_comparison_category_t<     std::compare_three_way_result_t<Types>...>     operator<=>( const std::variant<Types...>& v,                  const std::variant<Types...>& w );	(7)	(since C++20)

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.

7) Three-way comparison operator for variants:

• If both v.valueless_by_exception() and w.valueless_by_exception() are true, returns std::strong_ordering::equal;
• otherwise if v.valueless_by_exception() is true, returns std::strong_ordering::less;
• otherwise if w.valueless_by_exception() is true, returns std::strong_ordering::greater;
• otherwise if v.index() != w.index(), returns v.index() <=> w.index();
• otherwise equivalent to std::get<v.index()>(v) <=> std::get<v.index()>(w).

Parameters

v,w

-

variants to compare

Return value

The result of the comparison as described above.

See also

operator==operator!=operator<operator<=operator>operator>=operator<=> (C++17)(C++17)(C++17)(C++17)(C++17)(C++17)(C++20)

compares optional objects (function template)