std::pmr::operator==, std::pmr::operator!=

Since C++17

// 1)
template< class T1, class T2 >
bool operator==( const std::pmr::polymorphic_allocator<T1>& lhs,
                 const std::pmr::polymorphic_allocator<T2>& rhs ) noexcept;
// 2)
friend bool operator==( const polymorphic_allocator& lhs,
                        const polymorphic_allocator& rhs ) noexcept;
// 3)
template< class T1, class T2 >
bool operator!=( const std::pmr::polymorphic_allocator<T1>& lhs,
                 const std::pmr::polymorphic_allocator<T2>& rhs ) noexcept; // until C++20
// 4)
friend bool operator!=( const polymorphic_allocator& lhs,
                        const polymorphic_allocator& rhs ) noexcept;        // until C++20

Compares two polymorphic allocators. Two polymorphic allocators compare equal if their underlying memory resource compares equal.

1. Returns *lhs.resource() == *rhs.resource()

2. Same as (1), allowing conversion to polymorphic_allocator.

   This function is not visible to ordinary unqualified or qualified lookup, and can only be found by argument-dependent lookup when std::pmr::polymorphic_allocator is an associated class of the arguments.

3. Returns `!(lhs == rhs)

4. Same as (3), allowing conversion to polymorphic_allocator.

   This function is not visible to ordinary unqualified or qualified lookup, and can only be found by argument-dependent lookup when std::pmr::polymorphic_allocator is an associated class of the arguments.

The != operator is synthesized from operator== (since C++20)

Parameters

lhs, rhs - polymorphic allocators to compare

Return value

1-2) *lhs.resource() == *rhs.resource()
3-4) !(lhs == rhs)

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 3683	C++17	polymorphic_allocator could not be compared with types convertible to it	overload added