What are good alternatives to "using namespace std;"?

 

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  • Why is “using namespace std” considered bad practice? 35 answers

    • The main alternatives to bringing in everything from the std namespace into the global one with using namespace std; at global scope are:

  • Only bring in the actual names you need. For example just bring in vector with using std::vector;

  • Always use explicit namespace qualifications when you use a name. For example std::vector<int> v; (in headers, this should almost always be the only thing you do)

  • Bring in all names, but in a reduced scope (like only inside a function). For example void f() { using namespace std; vector<int> v; } void f() { using namespace std; vector<int> v; } void f() { using namespace std; vector<int> v; } - this does not pollute the global namespace.

    • The alternative is to write std:: everywhere. It's frowned upon because of name collisions and because it's unclear. If you just write vector I don't immediately know if you're using some math 3d vector or the standard library vector or something else. If you write std::vector it's clear. If you using namespace std , vector may collide with my own 3d math class called vector .

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