A
namespace is an optionally named scope. You declare names
inside a namespace as you would for a class or an enumeration. You can
access names declared inside a namespace the same way you access a nested
class name by using the scope resolution (::)
operator. However namespaces do not have the additional features of
classes or enumerations. The primary purpose of the namespace is to add
an additional identifier (the name of the namespace) to a name.
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