enum class cast?

[squarehead]

I am trying to set the value of an enum class type object with the value given by the user from the command prompt.

#include <iostream>

enum class EnergyState : unsigned char {
    ON,
    OFF
};

int main()
{
    EnergyState state;
    unsigned char s;
    std::cin >> s;
    state = static_cast<EnergyState>(s);    // Something goes wrong here?
    std::cout << static_cast<unsigned char>(state) << std::endl;    // Test
    std::cout << "Your computer is currently "
              << ((state == EnergyState::ON) ? "on" : "off")
              << "." << std::endl;
    return 0;
}

Is this type of assignment (state = static_cast<EnergyState>(s);) possible, or do I have to do something like this instead?

std::cin >> s;
if (s == 0)
    state = EnergyState::ON;
else if (s == 1)
    state = EnergyState::OFF;

[giblit]

EnergyState::On should be equal to 0 and off equal to 1. I would change state = static_cast<EnergyState>(s); to state = s or just simply remove the state part then at the end put ((s == EnergyState::ON) ? "on" : "off")

Sorry it should just be static_cast<EnergyState>(s-'0'); didn't realize you are using unsigned char instead of int.

[squarehead]

The problem was the use of unsigned char? I don't understand why there is a difference using unsigned short int for instance. Both unsigned char and unsigned short int are integral types.

The following seems to work just fine.

#include <iostream>

enum class EnergyState : unsigned short int {
    ON,
    SUSPENDED,
    OFF
};

int main()
{
    EnergyState state;
    unsigned short int s;
    std::cin >> s;
    state = static_cast<EnergyState>(s);
    std::cout << "Your computer is currently "
        << ((state == EnergyState::ON) ? "on" : (state == EnergyState::SUSPENDED) ? "suspended" : "off")
        << "." << std::endl;
    return 0;
}

[giblit]

When its a char it reads it in as '0' which is 48 in the ascii table and when you read in as an int it reads in as 0.

[squarehead]

Of course. How simple. Yet another one of those moments when I feel stupid and enlightened at the same time. Thank you.