Definition and use of C language namespace

as everyone knows std Is a namespace , It can define a series of constants , Variables and functions , The simplest namespace is defined as follows ：

namespace Output {
    
	int i = 10;
	const int con = 15;
	void printStr() {
    
		printf("hello");
	}
}
using namespace Output;

It defines a Output The namespace of , There is a constant in it , Variable , function . If we want to use them , It can be like this

Output::printStr()

You can call this function directly . Empathy ,std::bind() It's also a function , Only this function is defined in a namespace .