C++利用函数模板得到数组的长度

#include

template 
char (&ArraySizeHelper(T (&arr)[N]))[N];

#define arraysize(array) (sizeof(ArraySizeHelper(array)))

template 
int ArraySize (T (&arr)[N])
{           
    return N;  
}

int main() 
{ 
    int arr[10];
    std::cout << ArraySize(arr) << "," << arraysize(arr) << std::endl;
    double arr2[20];
    std::cout << ArraySize(arr2) << "," << arraysize(arr2) << std::endl;
    
    return 0;
}