Is it good practice to use multiple namespace in same C++ source file?

Question

I want to include more than one namespace in the same .cpp file.

While std is widely used, the namespace z3 will be used in about 10% of a 25 KLOC file.

Will it be a good practice to use both as

    using namespace std;
    using namespace z3;

I am thinking of using only std and then use the Z3 methods by mentioning the namespase whenever required. Like,

    using namespace std;

    z3::context c;
    z3::solver s;

Which of these is better practice?

I do not want to rename them into one namespace.

Thanks and regards, Sukanya

Answer 1

It's actually best practice not to import the entire namespace into your program because it pollutes your namespace. This can lead to naming collisions. It's best to import only what you are using.

So instead of:

using namespace z3;

You should do:

using z3::context;