Variadic template with template arguments in pairs

[Paul Backus]

On Wednesday, 12 September 2018 at 15:12:16 UTC, Anonymouse wrote:
> void doByPair(Args...)(Args args)
> if (Args.length)
> {
>     foreach (pair; args.pairwise)
>     {
>         static assert(is(typeof(pair[0]) == string));
>         static assert(isPointer!(pair[1]));
>         assert(pair[1] !is null);
>
>         string desc = pair[0];
>         auto value = *pair[1];
>         writefln("%s %s: %s", typeof(value).stringof, desc, 
> value);
>     }
> }

The easiest way is probably to iterate using indices with an 
increment of 2, e.g.:

static foreach(i; iota(0, args.length, 2))
{
     static assert(is(typeof(args[i]) == string));
     static assert(isPointer!(args[i+1]));

     // etc.
}

Another alternative is to write the function recursively:

void doByPair(T, Rest...)(string desc, T* valuePtr, Rest rest)
{
     writefln("%s %s: %s", T.stringof, desc, *valuePtr);
     if (rest.length) doByPair(rest);
}