Re: 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;
}