Unscoped Enumerations in C++

An unscoped enumeration defines the enumerators in the global namespace as shown below:

enum Color
{
    red,
    green,
    blue,
};
 
int main(int argc, char const *argv[])
{
    Color color{blue};
    
    return 0;
}

blue enumerator from enumeration Color is used without any scope resolution operator (::), although we could use Color::blue. This property creates problems like naming collisions and polluting the global namespace.

If we want to scope them, either we can use a namespace and define them in there or use scoped enumeration. Following example shows using a namespace.

namespace Color
{
    enum Color
    {
        red,
        green,
        blue,
    };
}

Now we have scoped Color enumerators to Color namespace.

References

1. https://www.learncpp.com/cpp-tutorial/unscoped-enumerations/