• Kayomn (37/37) Feb 26 2018 I've been experimenting with D's Better C mode, and I have a
• TheFlyingFiddle (10/47) Feb 26 2018 Don't think you can alias member variables directly.
• Kayomn (4/15) Feb 26 2018 Damn, was hoping to keep my structs as plain old data-structures.
• ketmar (3/23) Feb 26 2018 write `pos` as free function then, and use UFCS. there is no real

Kayomn <spam kayomn.net> writes:

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;
}

TheFlyingFiddle <none none.com> writes:

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();

Kayomn <spam kayomn.net> writes:

On Monday, 26 February 2018 at 21:04:51 UTC, TheFlyingFiddle 
wrote:
 On Monday, 26 February 2018 at 20:50:35 UTC, Kayomn wrote:
 [...]

 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();

Damn, was hoping to keep my structs as plain old data-structures. 
Thanks for the info, guess I won't be doing this then.

ketmar <ketmar ketmar.no-ip.org> writes:

Kayomn wrote:

 On Monday, 26 February 2018 at 21:04:51 UTC, TheFlyingFiddle wrote:
 On Monday, 26 February 2018 at 20:50:35 UTC, Kayomn wrote:
 [...]

 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();

 Damn, was hoping to keep my structs as plain old data-structures. Thanks 
 for the info, guess I won't be doing this then.

write `pos` as free function then, and use UFCS. there is no real 
difference. ;-)