Problems with duplicate names in C + +

See C + + video Tutorials-Fan Lie (2.91G) Video Learning notes collation.

Why should 1.c++ introduce namespaces (namespace)?

C + + introduces the concept of namespaces in order to avoid duplicate name problems, such as avoiding duplication of function names or variable name conflicts.

2. For example: Use the name space to write, you can have three name B variable name, but their values are different.

#include <iostream>
namespace a
{
    int b=5;
}
Namespace C
{
    int b=8;
}
int main ()
{
    int b=9;
    std::cout<<b<< "" <<a::b<< "" <<c::b<<std::endl;
    return 0;
}

Print results:

3. But if we don't use namespaces, obviously we can't define it:

int b=5;

int b=8;

int b=9;

This code is wrong and cannot be compiled.

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4. When renaming conflicts:

#include <iostream>
namespace a
{
    int b=5;
}
Namespace C
{
    int b=8;
}
int main ()
{
    using namespace A;
    using namespace C;
    int b=9;
    std::cout<<b;
    return 0;
}

Print results:

The output is the value 9 in main function main.

If we comment out the int b=9 in the main function; You will not be able to compile and a B-ambiguous symbol error appears.

Author: cnblogs Nebula