D Properties when?

[jmh530]

On Thursday, 14 December 2023 at 18:08:52 UTC, Hipreme wrote:
> This is no news in the programming world, yet, we still don't 
> have it.
>
> This is very important for I can define a good API in which I 
> could increase my engine performance.
> With that, I could implement fields with dirty flags and not 
> make the API looks dirty (no pun intended).
>
>
> Think of an object with X and Y position. I want to be able to 
> when its value changes, it sets a dirty flag to true. The 
> problem is that I'm unable to do `X+= 50` after that. I need to 
> do `X = X + 50`, this is not news but still makes the API 
> inconsistent and more verbose.
> I don't care how this is implemented, I only want this some day 
> to not make it look ugly.

I'm not entirely sure what you mean, but what about something 
like this:

```d
import std.stdio: writeln;

struct Direction
{
     int x;
     alias x this;
     private bool _dirty;
     void opOpAssign(string op: "+")(int rhs) {
         x += rhs;
         _dirty = true;
     }
}

struct Foo
{
     Direction x;
     Direction y;
     this(int x, int y) {
      	this.x = Direction(x);
         this.y = Direction(y);
     }
}

void main()
{
     auto f = Foo(1, 2);
     f.x += 50;
     writeln(f.x._dirty);
     writeln(f.y._dirty);
}
```