const int, member array size-CodePudding

My code basically:

class myclass : public singleton<myclass> {
    public:
        myclass();
    private:
        const float myfloat = 6000.0f;
        const int sz_arr = (int)myfloat;

        int arr[sz_arr];  // compiler complains about this line
};

Need to create arr at compile-time. Size of arr is known at compile-time! Ought to be computed based on myfloat value. How to achieve it? Also, myclass is singleton, only one instance of it is ever going to be created.

CodePudding user response：

Firstly, sz_arr can't be used to specify the size of the array, you need to make it static. And mark myfloat as constexpr to make it known at compile-time (and better for sz_arr too).

class myclass : public singleton<myclass> {
    public:
        myclass();
    private:
        constexpr static float myfloat = 6000.0f;
        constexpr static int sz_arr = myfloat; // implicit conversion is enough

        int arr[sz_arr]; 
};