19.6. union
: A Space-Saving Class
A union
is a special kind of class. A union
may have multiple data members, but at any point in time, only one of the members may have a value. When a value is assigned to one member of the union
, all other members become undefined. The amount of storage allocated for a union
is at least as much as is needed to contain its largest data member. Like any class, a union
defines a new type.
Some, but not all, class features apply equally to union
s. A union
cannot have a member that is a reference, but it can have members of most other types, including, under the new standard, class types that have constructors or destructors. A union
can specify protection labels to make members public
, private
, or protected
. By ...
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