opDispatch is grand!

[Ellery Newcomer]

On 04/10/2010 05:49 PM, so wrote:
>
> struct vector(T, uint N) {
> auto opDispatch(string s) const {
> static if(N>0 && ("x"==s || "r"==s)) return v_[0];
> static if(N>1 && ("y"==s || "g"==s)) return v_[0];
> static if(N>2 && ("z"==s || "b"==s)) return v_[0];
> static if(N>3 && ("w"==s || "a"==s)) return v_[0];
> static assert("boom!");
> }
> private:
> T[N] v_;
> }
>
> No unions, clean and all!
> Then why do we need properties?

Can you get

vector!(int,3) v;
v.x = 1;

to work?


The closest I can get is

struct vector(T, uint N) {
     ref T opDispatch(string s )() {
         static if(N>0 && ("x"==s || "r"==s)) return v_[0];
         static if(N>1 && ("y"==s || "g"==s)) return v_[1];
         static if(N>2 && ("z"==s || "b"==s)) return v_[2];
         static if(N>3 && ("w"==s || "a"==s)) return v_[3];
         static assert("boom!");
     }
     private:
     T[N] v_;
}

..

vector!(int, 3) v;
v.x() = 1;


when DMD sees

v.x = 1;

it tries to rewrite it as v.x(1);

And I can't figure out how to overload opDispatch