C++ vs D: Default param values and struct to array casting

[Paul Backus]

On Friday, 6 September 2019 at 09:28:57 UTC, Andrew Edwards wrote:
> This is my thought on how to accomplish op overloading:
>
> struct Test
> {
>     float a, b, c, d;
>     float opIndex(size_t i)
>     in(i >= 0 && i <= 3)
>     {
>         final switch(i)
>         {
>             case 0: return a;
>             case 1: return b;
>             case 2: return c;
>             case 3: return b;
>         }
>     }
>
>     void opIndexAssign(float val, size_t i)
>     in(i >= 0 && i <= 3)
>     {
>         final switch(i)
>         {
>             case 0: a = val; break;
>             case 1: b = val; break;
>             case 2: c = val; break;
>             case 3: d = val; break;
>         }
>     }
> }
>
> Please advise if I've gone off the beaten path. It seems 
> overkill for the two lines of code C++ requires so any 
> suggestion is greatly appreciated.

You can use `static foreach` to eliminate the repetition in the 
switch statements. For example:

float opIndex(size_t i)
     in (i < typeof(this).tupleof.length)
{
     final switch (i) {
         static foreach (fid, field; typeof(this).tupleof) {
             case fid: return field;
         }
     }
}