Namespace aliases

 

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Declarators Reference Pointer Array Block declarations Simple-declaration   →Structured binding declaration(C++17) Alias declaration(C++11) Namespace alias definition using declaration using directive static_assert declaration(C++11) asm declaration Opaque enum declaration(C++11) Other declarations Namespace definition Function declaration Class template declaration Function template declaration Explicit template instantiation(C++11) Explicit template specialization Linkage specification Attribute declaration(C++11) Empty declaration

 

Namespace aliases allow the programmer to define an alternate name for a namespace.

They are commonly used as a convenient shortcut for long or deeply-nested namespaces.

Syntax

namespacealias_name = ns_name;	(1)
namespacealias_name = ::ns_name;	(2)
namespacealias_name = nested_name::ns_name;	(3)

Explanation

The new alias alias_name provides an alternate method of accessing ns_name.

alias_name must be a name not previously used. alias_name is valid for the duration of the scope in which it is introduced.

Keywords

namespace

Example

Run this code

#include <iostream>   namespace foo {namespace bar {namespace baz {int qux =42;}}}   namespace fbz = foo::bar::baz;   int main(){std::cout<< fbz::qux<<'\n';}

Output:

42

See also

namespace declaration	identifies a namespace
type alias declaration (C++11)	creates a synonym for a type