Can this macro be converted to a function?

Question

While refactoring code and ridding myself of all those #defines that we\'re now taught to hate, I came across this beauty used to calculate the number of elements in a struc

Answer 1

I prefer the enum method suggested by [BCS](in Can this macro be converted to a function?)

This is because you can use it where the compiler is expecting a compile time constant. The current version of the language does not let you use functions results for compile time consts but I believe this coming in the next version of the compiler:

The problem with this method is that it does not generate a compile time error when used with a class that has overloaded the '*' operator (see code below for details).

Unfortunately the version supplied by 'BCS' does not quite compile as expected so here is my version:

#include 
#include 
#include 


template
struct StructSize
{
    private:    static T x;
    public:      enum { size = sizeof(T)/sizeof(*x)};
};

template
struct StructSize
{
    /* Can only guarantee 1 item (maybe we should even disallow this situation) */
    //public:     enum { size = 1};
};

struct X
{
    int operator *();
};


int main(int argc,char* argv[])
{
    int data[]                                  = {1,2,3,4,5,6,7,8};
    int copy[ StructSize::size];

    std::copy(&data[0],&data[StructSize::size],©[0]);
    std::copy(©[0],©[StructSize::size],std::ostream_iterator(std::cout,","));

    /*
     * For extra points we should make the following cause the compiler to generate an error message */
    X   bad1;
    X   bad2[StructSize::size];
}