constexpr value_type& value() const;

Preconditions: empty() == false.

Returns: A reference to the value_type subobject in the container-node-type object pointed to by ptr_.

Preconditions: empty() == false.

Returns: A non-const reference to the key_type member of the value_type subobject in the container-node-type object pointed to by ptr_.

Remarks: Modifying the key through the returned reference is permitted.

constexpr mapped_type& mapped() const;

Preconditions: empty() == false.

Returns: A reference to the mapped_type member of the value_type subobject in the container-node-type object pointed to by ptr_.

constexpr allocator_type get_allocator() const;

Preconditions: empty() == false.

constexpr explicit operator bool() const noexcept;

Returns: ptr_ != nullptr.

constexpr bool empty() const noexcept;

Returns: ptr_ == nullptr.