Re: how to do this meta-programming? print the address of random element's address of a variable length of arrays?

[mw via Digitalmars-d-learn]

On Saturday, 12 September 2020 at 14:31:59 UTC, Paul Backus wrote:
On Saturday, 12 September 2020 at 03:19:23 UTC, mw wrote:
I.e. I want to learn the generic meta-programming way to 
assemble such parameter list (&(x[i], &(y[j])) at compile 
time, it is possible?

It's possible if you use a helper function. Here's how:

import std.meta: allSatisfy;
import std.traits: isArray;

void printRandomElemAddr(Arrays...)(Arrays arrays)
    if (allSatisfy!(isArray, Arrays))
{
    auto randomElemAddr(size_t i)()
        if (i < arrays.length)
    {
        import std.random: uniform;

        return &arrays[i][uniform(0, $)];
    }

    import std.stdio: writeln;
    import std.meta: staticMap, aliasSeqOf;
    import std.range: iota;

    writeln(staticMap!(randomElemAddr, 
aliasSeqOf!(iota(arrays.length))));
}

void main()
{
    int[] a = [1];
    int[] b = [2, 3];
    double[] c = [4, 5, 6];

    printRandomElemAddr(a);
    printRandomElemAddr(a, b);
    printRandomElemAddr(a, b, c);
}

Thanks, this works. staticMap and aliasSeqOf is the key.

Now, let me expand this challenge: suppose we need to add a new 
set of variable length extra parameters in parallel to the 
arrays, i.e:

     // just use scalar type for demo
     int    extraA;
     string extraB;
     double extraC;

     // need to be called as:
     printRandomElemAddr(extraA, a);
     printRandomElemAddr(extraA, extraB, a, b);
     printRandomElemAddr(extraA, extraB, extraC, a, b, c);


basically, two sets of variadic parameters, but need to be 
treated differently:

-- the 1st scalar set, just use as it is
-- the 2nd array set, need some processing (which you have done).

Now the question is how to pass & handle 2 sets of variadic 
parameters?