26 Containers library [containers]

26.2 Container requirements [container.requirements]

26.2.4 Node handles [container.node]

26.2.4.4 node_­handle observers [container.node.observers]

value_type& value() const;
Requires: empty() == false.
Returns: A reference to the value_­type subobject in the container_­node_­type object pointed to by ptr_­.
Throws: Nothing.
key_type& key() const;
Requires: 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_­.
Throws: Nothing.
Remarks: Modifying the key through the returned reference is permitted.
mapped_type& mapped() const;
Requires: 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_­.
Throws: Nothing.
allocator_type get_allocator() const;
Requires: empty() == false.
Returns: *alloc_­.
Throws: Nothing.
explicit operator bool() const noexcept;
Returns: ptr_­ != nullptr.
[[nodiscard]] bool empty() const noexcept;
Returns: ptr_­ == nullptr.