Aliasing member's members

[TheFlyingFiddle]

On Monday, 26 February 2018 at 20:50:35 UTC, Kayomn wrote:
> I've been experimenting with D's Better C mode, and I have a 
> question regarding something that I started thinking about 
> after watching one of Jonathon Blow's talks on data-oriented 
> programming - more specifically the aspect of fake "inheritance"
>
> I have the following code. My question is if it's possible to 
> use alias in a similar way to Jonathon's own language Jai and 
> its using keyword, referencing the internal Vector2 as 
> Player.pos instead of Player.entity.position:
>
> import core.stdc.stdio : printf;
>
> uint idCounter = 0;
>
> struct Vector2 {
> 	double x,y;
> }
>
> struct Entity {
> 	uint id;
> 	Vector2 position;
> }
>
> struct Player {
> 	Entity entity;
>
> 	alias pos = Entity.position;
> }
>
> Player createPlayer(Vector2 position) {
> 	Player player;
> 	player.entity.id = idCounter++;
> 	player.entity.position = position;
>
> 	return player;
> }
>
> int main(string[] args) {
> 	Player player = createPlayer(Vector2(50.0,50.0));
>
> 	printf(
> 		"[Player]\nid: %d\nPosition: %lf x %lf\n",
> 		player.entity.id,
> 		player.pos.x,
> 		player.pos.y
> 	);
>
> 	return 0;
> }

Don't think you can alias member variables directly.

You could do this though:

struct Player {
     Entity entity;

     ref auto pos() inout { return entity.position; }
}

Which will give you most of what you want. Although if you want 
to take the address of pos you have to use

auto addr = &player.pos();