Array operations with array of structs

[Nicholas Wilson via Digitalmars-d-learn]

On Monday, 6 July 2015 at 01:16:54 UTC, Peter wrote:
> Hi,
> I have a struct with arithmetic operations defined using 
> opBinary but array operations with arrays of it don't work.
>
> struct Vector3 {
>     public double[3] _p;
>     ...
>     Vector3 opBinary(string op)(in Vector3 rhs) const
>     if (op == "+"){
>         Vector3 result;
>         result._p[] = this._p[] + rhs._p[];
>         return result;
>     }
>     ...
> }
>
> unittest{
>     auto a = Vector3([2.0, 2.0, 0.0]);
>     auto b = Vector3([1.0, 2.0, 1.0]);
>     Vector3[] c = [a];
>     Vector3[] d = [b];
>     Vector3 e = a + b; // works
>     Vector3[] f;
>     f[] = c[] + d[]; // Error: invalid array operation 'f[] = 
> c[] + d[]' because Vector3 doesn't support necessary arithmetic 
> operations
> }
>
> how can I get this to work?
>
> Thanks

you need to define the slice operators. e.g.

auto opSlice() // no parameters to get whole slice eg. a[]
                       // can also define with opSlice(size_t i, 
size_t j)
                       // for access like a[ i .. j]
{
     return _p;
}