Question

I am trying to do the following:

    switch(moveDirection){
        case MOVE_DIRECTION_UP:
            //do something
        break;
    }

Where MOVE_DIRECTION_UP is this:

    const unsigned char MOVE_DIRECTION_UP = 0x0;

The compiler gives the error: MOVE_DIRECTION_UP cannot appear in constant-expression

Surely this should be allowed, because it compiles fine if I replace MOVE_DIRECTION_UP with 0x0.

Any help is appreciated, thanks!

Answer 1

If you’re working with C++11, you can declare MOVE_DIRECTION_UP as a constexpr. The compiler will regard it as a constant value that can be used as a switch label.

If you’re not, you may define an enumeration:

namespace eDirection { enum e {
    UP = 0x0,
    DOWN = 0x1
};}

switch( direction ) {
    case eDirection::UP: ...
};