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

From cppreference.com
< cpp‎ | error‎ | error category
Utilities library
General utilities
Relational operators (deprecated in C++20)
Integer comparison functions
(C++20)(C++20)(C++20)
(C++20)
Swap and type operations
(C++20)
(C++14)
(C++11)
(C++23)
(C++11)
(C++23)
(C++11)
(C++17)
Common vocabulary types
(C++11)
(C++17)
(C++17)
(C++17)
(C++11)
(C++11)
(C++17)
(C++17)
(C++23)



std::error_category
Member functions
error_category::operator==error_category::operator!=error_category::operator<error_category::operator<=>
(until C++20) (until C++20) (C++20)
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
2) Checks whether *this and rhs
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==

(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
2) true if *this and rhs do not refer to the same object, false
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