“enum class” emulation or solid alternative for MSVC 10.0

Question

I\'m looking for a hacky kind of solution to the following problem: GCC 4.4+ accepts the following c++0x code:

enum class my_enum
{
    value1,
    value2
};         


        

Answer 1

I just discovered a problem with James' good hack (which I have heretofore been using), and a fix to the problem. I discovered the problem when I tried to define a stream operator for my_enum.

#include 

struct my_enum {
    enum type { 
        value1, 
        value2 
    };

    my_enum(type v) : value_(v) { }

    operator type() const { return value_; }

private:

    type value_;
};

std::ostream&
operator<<(std::ostream& os, my_enum v)
{
    return os << "streaming my_enum";
}

int main()
{
    std::cout << my_enum::value1 << '\n';
}

The output is:

0

The problem is my_enum::value1 has different type than my_enum. Here's a hack to James' hack that I came up with.

struct my_enum
{
    static const my_enum value1;
    static const my_enum value2;

    explicit my_enum(int v) : value_(v) { }

    // explicit // if you have it!
       operator int() const { return value_; }

private:

    int value_;
};

my_enum const my_enum::value1(0);
my_enum const my_enum::value2(1);

Notes:

1. Unless otherwise specified by an enum-base, the underlying type of a scoped enumeration is int.
2. Explicit conversions to and from the underlying integral type are allowed. But implicit conversions are not. Do your best.
3. This hack is more of a pita than James' because of the need to enumerate the values twice. I'm hoping compilers without scoped enum support rapidly become extinct!