PyD-like wrapping for Excel/VBA and Julia?

[Laeeth Isharc via Digitalmars-d-learn]

I have a bunch of D functions I would like to make available to 
Excel (and possibly Julia) without having to write wrappers for 
each function individually.

For Excel, I think one needs two levels of wrapper - one is to 
create a C style interface [using extern(Windows) calling 
convention, and pointers to doubles or structs rather than 
dynamic arrays], and the second is to write the VBA wrapper that 
calls the C interface.  (There may be more efficient purer ways 
of doing this, but I don't wish to spend time learning Excel 
internals/object models, and I know my route will work reasonably 
well).

So a very simple D function:
double test(double[] inp,  ref double[] oup)
{
        double sum=0.0;
        oup.length=inp.length;
        foreach(i;0..inp.length)
        {
                oup[i]=inp[i]*inp[i];
                sum+=oup[i];
        }
        return sum;
}

and my first attempt at a wrapper:

extern(Windows) double vbwrap_test(double* inp,size_t 
num_inp,double* oup,size_t num_oup)
{
        double[] arg_inp;
        arg_inp.length=num_inp;
        double[] arg_oup;
        arg_oup.length=num_oup;
        foreach(arg;0..num_inp)
        {
                arg_inp[arg]=inp[arg];
        }

        foreach(arg;0..num_oup)
        {
                arg_oup[arg]=oup[arg];
        }

        return test(arg_inp,arg_oup);
}

I didn't yet write the bit that copies the result from test back 
to the calling double*.

Slowly learning metaprogramming/CTFE in D, and the code above was 
generated from the function definition by some horrible looking D 
code, ready to place into a string mixin.  I need to make it more 
general (to accept structs etc), and write the VBA wrapper 
generation too.

But if anyone has any useful pointers or suggestions or would 
like to help, do let me know.  I guess this project could be of 
broader application since in the financial and other sectors 
people still are stuck with Excel as a front end in many cases, 
for better or for worse.

I will look at LuaD and PyD and Adam's web.d for inspiration..

Julia was just something to think about further down the line.  I 
haven't used it much yet.


Thanks.


Laeeth.