How to convert this C code to C++?

Question

I have some arrays that are declared like this:

static double covalent_radius[256] = {
    [ 0 ] = 0.85,
    [ 1 ] = 0.37,
    ...
};

C++ doesn't allow this kind of declaration. Is there any way to achieve this?

Answer 1

static double covalent_radius[256] = {
    0.85, /* ?,  Unknown    */
    0.37, /* H,  Hydrogen   */
    ...
};

It's C89, not C99 so I suppose it should work.

Answer 2

Why don't you do this:

static double covalent_radius[256] = {
    0.85, /* 0: ?,  Unknown    */
    0.37, /* 1: H,  Hydrogen   */
    ...
};