CODEWITHSUNDEEP
c++
Rick
Rick

Reputation: 7506

Why can't cout a scoped enum class member directly while can for unscoped enum?

cout unscoped enum directly works:

#include <iostream>
using namespace std;
enum  color { red, green, blue };

int main()
{
    cout << color::green;
    return 0;
}

While with socoped enum can't:

#include <iostream>
using namespace std;
enum class color { red, green, blue };

int main()
{
    cout << color::green;
    return 0;
}

What's the difference?

Upvotes: 2

Views: 427

Answers (3)

Nikola Lukic
Nikola Lukic

Reputation: 4244

Maybe char like optimal attribute help you.

#include <iostream>

using namespace std;

enum class Color { red='r', green='g', blue='b' };

int main()
{

    cout << "Print opt attribute: " <<  static_cast<char>(Color::green);
    return 0;
}

Test online :

https://onlinegdb.com/Syw-qgg97

Upvotes: 0

Max Langhof
Max Langhof

Reputation: 23681

The unscoped enum is automatically converted to some integral type. That's why it will only print out 1, not green.

The scoped enum is not implicitly convertable to an integer and there is not other operator<< for std::cout so it fails to compile.

Upvotes: 1

Brian Bi
Brian Bi

Reputation: 119099

This works because unscoped enums can be implicitly converted to integers, whereas scoped enums can't, and require an explicit conversion:

cout << static_cast<int>(color::green);

Upvotes: 5

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