A D vs. Rust example

[Ola Fosheim Grøstad]

On Thursday, 27 October 2022 at 17:37:59 UTC, Quirin Schroll 
wrote:
> There aren’t many languages that have both, templates and 
> generics; C++/CLI and C++/CX are the only ones I know and I 
> happen to have some experience with them.

I have found that it is to some extent possible to do such type 
checks of generics with C++ concepts. I've made some attempts for 
a generic graphics library I've started on, but it gets tedious 
quite fast. I would imagine you could do some of the same in D in 
a more ad-hoc matter, but that would be even more tedious.

It basically involves setting up all the constraints and then 
test them with a single static assert (which involves 
instantiation, but in the definition file without explicitly 
using the instance methods).

The C++ concept-feature is helpful in this regard, but not 
helpful enough to make it pleasant… which basically limits my 
eagerness to use of it in practice. Still, a move in the right 
direction.

D has a chance to learn from C++ and create a better 
concept-feature. Don't replicate it, look at the use cases where 
C++ concepts become tedious or difficult to get right, then 
design something better.

> D could introduce generics and it would actually profit more 
> from them than e.g. C++ would because D has first-class 
> reference types and almost no user-defined implicit conversions.

This is probably true, but you could instead try to find a way to 
clearly specify and statically check template requirements.

> Imagine how much more attractive D would be to OO crowd if it 
> had first-class value type boxing, generics with variance and 
> wildcards, and all the other OO stuff modern OO-fist languages 
> offer. Using Java and C#, it feels like D only has the bare 
> minimum to call itself object-oriented.

That is a reasonable angle given the large number of programmers 
that have experience with Java and C#, but I think D could take a 
closer look at how templates are done and find out what is 
missing. When was the last time a feature was added to support 
generic programming?

> There was some talk (by Átila, IIRC) that having first-class 
> classes and OO in D was a design error. I have no idea whether 
> there is actually a plan to fade those out improve them to be 
> competitive on that front.

OO is not a mistake, I agree. I find it quite frustrating to not 
have inheritance when programming in Go. Just basic things like 
having a linked list node in the super class makes things much 
simpler/cost-efficient when you are mixing types in 
data-structures.