Correct programming with namespaces

Question

I wonder what is the right way to use namespace while calling functions or using classes from libraries. Should I always call a function in the format namespace::func()?

I'm a little bit confused because when I'm trying to use the function cout from <iostream> I always need to add the library namespace - std::cout.

But when I'm trying to call a function from <ctime> library which belongs to std namespace, I don't need to add the namespace before the function name.

Why is that?

Some functions are adopted from the global namespace regarding their plain c implementations are available. — πάντα ῥεῖ
– πάντα ῥεῖ, Commented Oct 8, 2018 at 19:10
mostly, in a module file, i would declare using namespace XXX; and use without XXX::, but in headers, i would not declare using namespace XXX; so it wont affect includers without their will. — Tomer W
– Tomer W, Commented Oct 8, 2018 at 19:16

Some programmer dude · Accepted Answer · 2018-10-08 19:10:42Z

7

The <ctime> header is a backward-compatibility header file against the old C roots of C++. Such compatibility headers can (and usually do) put their function both in the std namespace and in the global namespace.

Thus a function like std::time can be reached both as std::time and time.

answered Oct 8, 2018 at 19:10

Some programmer dude

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