About using namespaces

[tron.thomas]

If I remember correctly, in one of his books, Scott Meyers suggests
putting code into a custom namespace rather, and here I might be
paraphrasing, "polluting the global namespace" with type definitions
and such.

Assuming this is a good idea, I'm wondering about what happens when so
many people do the following:

using namespace std;

It seems like such a statement will bring a lot of stuff into the
global namespace, and a lot of it won't be used at all. Most people
only make use of a small portion what contained in the std namespace.

I'm wondering if it isn't better to only declare what someone wants to
use such as:

using std::vector;
using std::cout;

What kind of difference can it make to use either approach for
promoting items for a specific namespace for use in global scope?

 

[Daniel T.]

If I remember correctly, in one of his books, Scott Meyers suggests
putting code into a custom namespace rather, and here I might be
paraphrasing, "polluting the global namespace" with type definitions
and such.

Assuming this is a good idea, I'm wondering about what happens when so
many people do the following:

using namespace std;

It seems like such a statement will bring a lot of stuff into the
global namespace, and a lot of it won't be used at all. Most people
only make use of a small portion what contained in the std namespace.

I'm wondering if it isn't better to only declare what someone wants to
use such as:

using std::vector;
using std::cout;

What kind of difference can it make to use either approach for
promoting items for a specific namespace for use in global scope?

If "using namespace /X/" is contained within an individual translation
unit (a .cpp file) then it is a rather local "pollution" that can be
easily changed (assuming you aren't writing .cpp files that are
thousands of lines long.)

However putting using declarations or definitions in header files have a
much wider effect.

 

[Victor Bazarov]

If I remember correctly, in one of his books, Scott Meyers suggests
putting code into a custom namespace rather, and here I might be
paraphrasing, "polluting the global namespace" with type definitions
and such.

Assuming this is a good idea, I'm wondering about what happens when so
many people do the following:

using namespace std;

It seems like such a statement will bring a lot of stuff into the
global namespace, and a lot of it won't be used at all. Most people
only make use of a small portion what contained in the std namespace.

I'm wondering if it isn't better to only declare what someone wants to
use such as:

using std::vector;
using std::cout;

What kind of difference can it make to use either approach for
promoting items for a specific namespace for use in global scope?

I believe there is a FAQ on that. See 27.5.

V

 

[tron.thomas]

I believe there is a FAQ on that. See 27.5.

V

Where can the FAQ be found?

 

[Guest]

Please do not quote signatures.

Where can the FAQ be found?

Normally it can be found at http://www.parashift.com/c++-faq-lite/
though here have been some DNS problems so if that does not work try
http://www.coders2020.com/cplusplus-explained/index.html