Random thought: Alternative stuct

[Paul Backus]

On Tuesday, 4 September 2018 at 04:03:19 UTC, Mike Franklin wrote:
> There are also a few additional differences.  classes can 
> inherit implementations, but using the technique illustrated in 
> https://theartofmachinery.com/2018/08/13/inheritance_and_polymorphism_2.html, you can get something very much like classes.  With `alias this` and multiple-`alias this` (https://github.com/dlang/dmd/pull/8378) it gets even better.
>
> [...]
>
> In my opinion, we shouldn't add a third option.  Rather, we 
> should deprecate classes, and make and expand the capabilities 
> of structs.  Languages like Zig and Rust have done away with 
> classes and all runtime overhead that accompanies them, and are 
> showing great promise by expanding on structs with much more 
> composable features.

You can implement inheritance in C, if you really want to, but 
doing it by hand is far less productive and far more error prone 
than using a compiler that does it for you.

Now, with D's metaprogramming capabilities, it may well be 
possible to implement an object system as a library, using only 
structs. Without AST macros, though, a library solution is always 
going to have uglier syntax and worse error messages than a 
language feature with compiler support.

If D didn't have built-in OOP features already, it'd be an 
interesting question, but given that it does, I think getting rid 
of them is a clear net-negative.