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std::error_category::operator==,!=,<,<=>

bool operator==( const error_category& rhs ) const noexcept;
 (1) (since C++11) 
bool operator!=( const error_category& rhs ) const noexcept;
 (2) (since C++11)
(until C++20)		 
bool operator<( const error_category& rhs ) const noexcept;
 (3) (since C++11)
(until C++20)		 
std::strong_ordering operator<=>( const error_category& rhs ) const noexcept;
 (4) (since C++20)

Compares to another error category.

1) Checks whether *this and rhs refer to the same object.
2) Checks whether *this and rhs do not refer to the same object.
3) Orders *this and rhs by the order of this and &rhs. Equivalent to std::less<const error_category*>()(this, &rhs).
4) Orders *this and rhs by the order of this and &rhs. Equivalent to std::compare_three_way()(this, &rhs).

The <, <=, >, >=, and != operators are synthesized from operator<=> and operator== respectively.

 (since C++20)

Parameters

rhs - specifies the error_category to compare

Return value

1) true if *this and rhs refer to the same object, false otherwise.
2) true if *this and rhs do not refer to the same object, false otherwise.
3) true if *this is less than rhs as defined by the order of this and &rhs.
4) std::strong_order::less if *this is less than rhs as defined by the order of this and &rhs, otherwise std::strong_order::greater if rhs is less than *this in the order, otherwise std::strong_order::equal.

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