Issue Turning Template into Variadic Template

[ag0aep6g via Digitalmars-d-learn]

On 30.03.2016 20:12, jmh530 wrote:
> I wrote a version of cartesianProduct that will return the cartesian
> product when the some of the types are not ranges. The original code is
> below.
>
> My issue is that I can't figure out how to turn it into a variadic
> template. The latest thing I tried is:
>
> auto mixedCartesianProduct(T...)(T x)
> {
>      import std.algorithm : cartesianProduct;
>
>      foreach(t; x)
>              t = conditionalOnly(t);
>
>      return cartesianProduct(x);
> }

auto mixedCartesianProduct(T...)(T x)
{
     import std.algorithm : cartesianProduct;
     import std.meta: staticMap;
     import std.traits : ReturnType;

     alias ConditionalOnly(T) = ReturnType!(conditionalOnly!T);
     alias RangeTypes = staticMap!(ConditionalOnly, T);

     RangeTypes ranges;
     foreach (i, t; x) ranges[i] = conditionalOnly(t);

     return cartesianProduct(ranges);
}