Multiple namespace declaration in C++

Question

Is it legal to replace something like this:

namespace foo {    namespace bar {       baz();    } } 

with something like this:

namespace foo::bar {    baz(); } 

?

Answer 1

You can combine namespaces into one name and use the new name (i.e. Foobar).

namespace Foo { namespace Bar {     void some_func() {         printf("Hello World.");     } }}  namespace Foobar = Foo::Bar;  int main() {     Foobar::some_func(); } 

Answer 2

Pre C++17:

No, it's not. Instead of a bunch of indented nested namespaces, it's certainly valid to put them on the same line:

namespace Foo { namespace Bar { namespace YetAnother {     // do something fancy } } } // end Foo::Bar::YetAnother namespace 

C++17 Update:

You can now nest namespaces more cleanly in C++17:

namespace Foo::Bar::YetAnother {   // do something even fancier! }