Name
namespace keyword — Declares namespace
Synopsis
declaration := namespace-defn
block-decl := namespace-alias-defn | using-directive
namespace-defn ::= named-namespace-defn | unnamed-namespace-defn
named-namespace-defn ::= namespace identifier { namespace-body }
unnamed-namespace-defn ::= namespace { namespace-body }
namespace-body ::= [declaration-seq]
namespace-alias-defn ::= namespace identifier = namespace-specifier ;
namespace-specifier ::= [::] [nested-name ::] namespace-name
namespace-name ::= identifier
using-directive ::= using namespace namespace-specifier ;The namespace keyword can be
used in a namespace definition, a namespace alias definition, or a
using directive. A namespace is a
scope for declarations of classes, templates, functions, objects, and
other namespaces. Outside a namespace, you can refer to a name that is
declared in the namespace by qualifying the name with the scope
operator (::), such as ns::name, or with a using directive or declaration.
Multiple namespace declarations can name the same namespace,
each one adding more declarations to the namespace. The standard
namespace, std, is built this way,
with many different headers all placing their declarations in the
std namespace. A namespace can be
anonymous, which prevents the enclosed declarations from being visible
in other source files.
A namespace alias defines an identifier as a synonym for an
existing namespace. See using for
information on the using
directive.
Example
namespace math_version_2 { const ...